FRCPath Part 1 Examination in Clinical Biochemistry ......FRCPath Part 1 Examination in Clinical Biochemistry Specimen Short Answer Question Question provided for illustrative and

FRCPath Part 1 Examination in Clinical Biochemistry Specimen Short Answer Question

Question provided for illustrative and educational purposes. It has not undergone the full quality assurance process of live FRCPath questions and additional or alternative

Topic area: Calcium, magnesium, bone disease Question no: 1 Osteoporosis is a skeletal disease characterised by low bone mass and microarchitectural deterioration of bone tissue with a consequent increase in bone fragility and susceptibility to fracture. a) Give four major risk factors for

osteoporotic fracture [4] Four from: Age, female sex, low BMD, previous fracture, positive family history, susceptibility to fall

b) Name two of the most common sites for osteoporotic fracture? [4]

Two from Hip, vertebrae, wrist/distal forearm

c) What technique is used to measure bone mass? [2]

Dual energy X-ray absorptiometry

d) What is a T-score? [2] This is a bone mineral density result expressed in number of standard deviations below the young adult mean value.

e) Give 4 secondary causes of low bone mass. [4]

4 from: Steroids, transplant, primary hyperparathyroidism, hyperthyroidism, Cushing’s Syndrome, hyperprolactinaemia, female athlete, anorexia nervosa, inflammatory bowel disease, alcoholism, coeliac disease, liver disease (eg PBC), multiple myeloma, systemic mastocytosis etc

f) Name 2 drugs used to treat postmenopausal osteoporosis. [4]

Bisphosphonate, teriparatide, raloxifene, calcitonin, strontium ranelate (not calcium and vitamin D and not HRT)

answers may apply in some cases.



Topic area: Calcium, magnesium, bone disease Question no: 2

Osteoporosis is a progressive, systemic skeletal disease.

a) State four characteristics of

osteoporosis? [4] Low bone mass (allow reduced bone mineral density) Deterioration of the microarchitecture of bone tissue Susceptibility to fracture Altered bone proteins

b) What non-pathology test diagnoses osteoporosis? [2]

Duel emission X-ray absorptiometry (allow 1 mark for DEXA) scan

c) Name three causes of secondary osteoporosis, and a biochemical test that may be used to exclude each of these [6]

Three from: Endocrine or hypogonadism Deficiency states Inflammatory disease Haematological/neoplastic Drug-induced Genetic/congenital With a relevant investigation in each case

d) Name two of the most common sites for osteoporotic fractures? [2]

Two from: Distal forearm/wrist Hip Vertebrae

e) What class of drug is used in the treatment of osteoporosis? [2]

Bisphosphonates

f) Give two examples of lifestyle advice is given to patients with osteoporosis? [4]

Two from: Smoking cessation, avoid excess alcohol intake, increased weight-bearing exercise, adequate calcium and vitamin D intake





Biochemical hypophosphataemia is common in hospitalised patients, but may not indicate phosphate depletion.

a) Name 4 causes of hypophosphataemia

[4] Four from: Acute alcoholism, recovery phase of DKA, severe burns, inadequate phosphate in TPN, refeeding syndrome, severe respiratory alkalosis, fulminant hepatic failure, gram negative septicaemia, hyperparathyroidism, Cushing’s syndrome, hypothyroidism, hypomagnesaemia, hypokalaemia, theophylline intoxication, chronic diuretic use, phosphate binding antacids, starvation, malabsorption

b) State four consequences of severe, prolonged phosphate deficiency? [4]

Four from: Anorexia, muscle weakness, neuromuscular (seizures, encephalopathy or coma), haematological (haemolytic anaemia, impaired white cell and platelet function), respiratory depression, reduced cardiac output

c) What muscular complication may arise at very low phosphate concentrations? [2]

Rhabdomyolysis

d) What bony complications may arise in adults and children with chronic phosphate depletion? [4]

Children – Rickets Adults - osteomalacia

e) The most common method used to measure phosphate is based on the formation of a phosphomolybdate complex. Name the substrate used in this reaction [2]

Ammonium molybdate (allow one mark for molybdate)

f) The phosphomolybdate complex may be measured directly, or reduced to molybdenum blue. What is the advantage of measuring the reduced complex? [4]

Less interference [1] from haemolysis, icterus and lipaemia [1 for at least one of these] as measurement is at 600-700nm compared with 340nm for unreduced complexes [2] (allow 1 for higher or different wavelength)





Biochemical markers may be used in the assessment of metabolic bone diseases such as Paget’s disease, osteoporosis and osteomalacia

a) Define osteoporosis (2) A reduction in bone mass and strength

leading to increased susceptibility to fracture.

b) State four risk factors in the development of osteoporosis (4)

Four from: Ageing, early menopause Family history, Alcohol abuse Smoking, chronic glucocorticoid use, anorexia nervosa, amenorrhoea

c) State two markers of bone resorption (2) Two from: CTX, NTX and Dpd

d) Explain the benefits of bone resorption markers in osteoporosis. (4)

Identifies much earlier response to treatment than BMD (2), may detect rapid bone loss and fracture risk (2).

e) Name the class of drug used as first line treatment for postmenopausal osteoporosis and state its action in the bone remodelling process. (4)

Bisphosphonates (2), inhibit osteoclast mediated bone resorption (2).

f) Describe two preanalytical factors that may influence the concentration of a marker (4).

Two from: Diurnal variation, fasting status, pre menopausal/menopausal status, exercise.




Topic area: Calcium, magnesium, bone disease Question no: 5 Phosphaturia is relatively common. Rare causes include genetic forms of hypophosphataemic vitamin-D resistant rickets a) How does hypophosphataemic vitamin

D-resistant rickets present? [4] May be positive family history [1] Otherwise minimal problems before child starts to walk when progressive lower limb deformities develop [1]. Growth rate is impaired. [1] Later in childhood/early adulthood dental problems (abcesses) may be problematic [1]

b) Indicate the expected biochemical abnormalities in serum/plasma observed in this condition. [5]

Two from: Low PO4, normal calcium, raised alkaline phosphatase [2] Parathyroid hormone normal [1] 25-hydroxyvitamin D normal [1] 1.25 dihydroxyvitamin D unexpectedly low [1]

c) What is the major regulated step in renal phosphate handling and how is it thought to be regulated? [5]

Major regulated step is activity of sodium –phosphate co-transporter (NPT 2a) in proximal tubule. [2] NPT2a reduced by PTH and fibroblast growth factor 23 (FGF 23) [2] NPT2a increased by reduction in dietary phosphate [1]

d) What are the two main methods of treatment of hypophosphataemic vitamin D resistant rickets? [2]

High dose oral phosphate supplements Supraphysiological doses of calcitriol to

e) State two the potential long-term complications of this treatment? [2]

Nephrocalcinosis Secondary/tertiary hyperparathyroidism

f) What is the cause of vitamin-D resistant rickets when the serum 1,25-dihydroxyvitamin D is elevated? [2]

Inactive 1,25-dihydroxy vitamin D [1] owing to receptor defect [1]




Topic area: Cancer Question no: 1

A GP requests an alpha-feto protein, AFP, test on his patient. The Clinical details are “Jaundice, query cause?”

a) What is the physiological function of

AFP? [2] The fetal counterpart [1] of albumin [1]

b) State two causes of a raised serum AFP concentration in non-pregnant adults [2]

Two from Hepatocarcinoma Germ cell tumours Testicular cancer Liver disease (cirrhosis) Liver metastases,

c) What two causes can result in an abnormally raised AFP during pregnancy? [4]

Neural tube defect Multiple pregnancy

d) What is the half-life of AFP? [2] 6 days (allow 5 to 7)

e) Give two ways in which the laboratory do to aid clinicians in comparing AFP results across different hospitals [4]

Two from Add a comment to show which method was used to produce the result. Keep accurate records of methods in use. Maintain good EQA performance Report as multiples of the median

f) Discuss the use of AFP in this GP patient’s investigation [6]

• Jaundice suggests raised bilirubin. • Bilirubin could be from liver –

cirrhosis/hepatocarcinoma could be part of differential

• Bilirubin could be from non-liver pathology

• Better to ascertain bilirubin origin first, and use AFP second line.

• High AFP level can be diagnostic of cancer but only if >4x normal value.

• AFP test expensive relative to other investigations




Topic area: Cancer Question no: 2

A 56-year old woman with a history of alcohol abuse and liver cirrhosis attended A&E with acute abdominal pains. A panel of tumour markers were requested with results as follows: AFP = 5 kU/L (<7) CA125 = 48 kU/L (<35) CA199 = <10 kU/L (<33) CEA = 3 µg/L (<5)

a) Name two possible causes of elevated CA125 in this lady [2]

Two from: Ovarian cancer, cirrhosis, ascites, pancreatitis, inflammation of GI tract, peritonitis

b) The biomarkers listed above are proteins produced by the tumour cell. State another class of molecule that is currently used as a tumour biomarker giving one example plus the malignancy it is most associated with. [2]

Hormones: e.g ACTH; pituitary, Calcitonin; medullary thyroid cancer Enzymes eg LDH; germ cell, NSE; lung Neurotransmitters: eg noradrenaline; phaeochromocytoma, dopamine; neuroblastoma.

c) Give two reasons why tumour markers should not be used in isolation to diagnose malignancy [4]

Inadequate sensitivity; low result cannot exclude malignancy. [2] Inadequate specificity; may be elevated in benign conditions. [2]

d) Give two general examples of when the measurement of tumour markers is clinically useful [2]

Monitoring response to therapy [2] Detection of recurrence after treatment or period of remission. [2]

e) List three properties of the ideal cancer biomarker [6]

Three from: Detectable only when tumour is present. Sensitive enough to detect small treatable tumours. Specific for type and site of malignancy Correlate with tumour burden. Respond rapidly to change in tumour size.

f) Using hCG as an example, briefly discuss the analytical problems associated with tumour marker assays. [4]

Include following up to maximum of four: Assay standardisation: [1] Heterogeneous molecule [1] (intact, core fragment, nicked, hyperglycosylation); different manufactures use antibodies with differing specificities. [1] Biological variation [1]: Different tumours produce different forms of hCG [1]; international reference preparation may not represent biological specimen [1]




Topic area: Cardiovascular system Question no: 1

Heart failure is a complex clinical condition in which a cardiac abnormality reduces the ability of the heart to pump blood.

a) State two causes of heart failure [4] Two from:

Coronary artery disease, myocarditis cardiomyopathy, volume overload, obstruction to outflow, obligatory high output (e.g. anaemia, thyrotoxicosis), compromised ventricular filling, altered rhythm (accept other credible answer)

b) Which system is activated in heart failure, as a result of diminished renal perfusion? [2]

Renin-angiotensin-aldosterone system

c) Measurement of B-type natriuretic peptide (BNP) may be used in the diagnosis of heart failure. State two actions of BNP. [4]

Two from: Natriuresis, diuresis, vasodilation, smooth muscle relaxation, antagonist of renin-angiotensin system

d) State a cause of a false positive and a false negative BNP result. [4]

False positive: Failure to adjust cut-offs for age or sex, high sodium diet, exercise, renal failure, acute coronary syndrome, acute pulmonary embolism (accept other credible answer) False negative: Failure to adjust cut-offs for age or sex, flash pulmonary oedema, acute mitral regurgitation, mitral stenosis, atrial myxoma

e) With reference to standardisation, what advantage does measurement of BNP have over NT-pro- BNP? [4]

BNP – all major commercial assays are calibrated to the same standard (Biosite-based standard) NT-pro-BNP – different assays use different antibodies – lack of standardisation due to molecular heterogeneity of degradation products

f) What is the gold-standard test for heart failure? [2]

Cardiac echocardiography




Topic area: Chromatography Question no: 1

Liquid Chromatography (LC) is a separation technique used in the quantification of a wide variety of biological molecules.

a) Name four types of liquid

chromatography (4) Four from: Ion exchange, affinity, size exclusion (gel filtration), partition and adsorption

b) Explain why sample preparation procedures may be required. (4)

Sample purification (2), and making sample amenable for detection (2)

c) List two methods of sample preparation (4)

Two from: Liquid extraction Solid phase extraction Derivitization

d) Define gradient elution (2) A steady change in mobile phase composition during chromatographic run

e) What is the benefit of gradient elution (2)

To accelerate the elution of strongly retained solutes.

f) State two limitations of HPLC (4) Two of: Expensive hardware, Requires experienced operators, Possibility of interferences (co-elution)




Topic area: Chromatography Question no: 2

High performance liquid chromatography (HPLC) is a popular technique in the clinical chemistry laboratory

a) What is the difference between isocratic

and gradient modes in HPLC? [4] In the isocratic mode, the mobile phase composition remains constant throughout the run. In gradient elution, the mobile phase composition is changed throughout the run [3], either in a step-wise or continuous manner [1]

b) What is the most widely used stationary phase for HPLC? [2]

Silica

c) Describe the difference between normal phase and reverse phase HPLC. [4]

In normal phase the functional groups of the stationary phase are polar relative to the mobile phase, which usually consists of non-polar solvents such as hexane or pentane [2]. Reverse phase involves a non-polar stationary phase [2]

d) Name two commonly used detectors in HPLC [2]

Two from: Visible light, UV light, diode array absorbance, fluorimeter, electrochemical

e) State one modification that can be made to improve

a) Sensitivity [2] and

b) Specificity [2]

Sensitivity: Smaller internal diameter of column Suppressor (to minimise ‘pump pulsations’) Fluorescence detection HPLC-MS Specificity: Use of restricted access column packing Chiral column packing Change polarity of mobile phase Column selection

f) Name two modifications that can be made to improve sample throughput [4]

Two from: Automated sample injection Restricted access column packing (allows direct injection of biological samples – no sample preparation) Gradient elution




Topic area: Diabetes mellitus and glucose Question no: 1 A 15-year-old boy, diagnosed with Type 1 diabetes mellitus 6 years previously, presented with a 36-hour history of malaise, abdominal pain, and a reduced conscious level. On examination he was drowsy and breathing rapidly and deeply. His biochemistry on admission was as follows: Serum sodium 122 mmol/L potassium 5.8 mmol/L bicarbonate 8.0 mmol/L urea 15.6 mmol/L creatinine 454 µmol/L Plasma glucose 54.0 mmol/L Urine ketones +++ a) Which ketone body species is likely to

be present in the largest concentration? [2]

β-hydroxbutyrate

b) Which ketone body species is most readily detected by dipstick tests for ketone? [2]

Acetoacetate

c) What are the two most likely causes for the hyperkalaemia? (4)

Exchange of intracellular K+ for H+ Impaired renal excretion of potassium

d) Other than renal impairment, what is the most likely explanation for the high creatinine result, and how might this be differentated? [4]

Interference by ketones with the kinetic Jaffe reaction (method dependent). Use either an enzymatic creatinine method or an alternative Jaffe method which is not prone to ketone interference

e) 12 hours after the initiation of treatment with insulin, 0.9% saline and potassium chloride his sodium was 140mmol/L and his glucose was 6.0mmol/L. What is the explanation for the rise in his serum sodium? [4]

The osmotic effect of hyperglycaemia on extracellular fluid

f) State two possible causes for this episode of diabetic ketoacidosis? [4]

Missed taking insulin Underlying infection (or inflammation)




Topic area: Diabetes mellitus and glucose Question no: 2 Diabetes Mellitus (DM) is a metabolic disorder of multiple aetiology characterised by chronic hyperglycaemia with disorders of carbohydrate, protein and fat metabolism resulting from defects in insulin secretion, insulin action, or both a) Diabetes can be categorised as Type 1

and type 2 diabetes. List 3 clinical features that suggest a diagnosis of Type 1 rather than type 2 [6]

Type 1 typically has a sudden onset. Type 1 more likely to present with weight loss Ketonuria/ ketoacidosis present Type 2 unlikely in patients with BMI <25/type 1 more likely in patients with BMI <25. . Type 1 earlier age of onset than type 2.

b) The incidence of Type 2 diabetes is rising. Give 2 possible reasons for this [2]

Aging population Increasing incidence of obesity

c) List 2 chronic complications of Type 2 diabetes [2]

Atherosclerosis/ increased CV risk Retinopathy Neuropathy Nephropathy

d) State the biochemical WHO diagnostic criteria for diagnosis of diabetes [6]

Random venous plasma glucose ≥ 11.1mmol/L [2] Fasting plasma glucose ≥7.0mmol/L [2] Plasma glucose ≥ 11.1mmol/L at 2 hours after an OGTT [2]

e) What antibodies may be measured to assist in diagnosis of Type 1 diabetes [2]

GAD antibodies (allow islet cell antibodies)

f) Maturity onset diabetes of the young (MODY) is a relatively rare familial form of diabetes. What is its most common mode of inheritance? [2]

Autosomal dominant mode of inheritance.




Topic area: Electrophoresis Question no: 1 Capillary electrophoresis is electrophoresis in capillary format. It is the most efficient and versatile separation technique for analysis of small and large molecules and is commonly used in clinical laboratories. a) List two modes of separation used in

capillary electrophoresis [2] Two from: Capillary zone electrophoresis (CZE) Micellar electrokinetic capillary chromatography (MECC) Capillary gel electrophoresis (CGE)

b) State how capillary zone electrophoresis separates species [2]

Charged species are separated according to their mobility (speed and direction of movement) in an aqueous solution under the influence of an applied field

c) Outline what is meant by the term electro-osmosis [6]

Movement of buffer solution in a capillary under the influence of an electric field [2]. Silanol groups on the stationary phase become negatively charged and attract positive ions present in solution [2]. Under the influence of an electric field the cations migrate to the cathode, dragging ions in solution and creating an electro-osmotic flow [2]

d) State four components of a capillary zone electrophoresis system [4]

Four from: High voltage power supply Fused silica capillary Electrodes Buffers Online detector

e) State two advantages of capillary zone electrophoresis over standard electrophoretic separation techniques? [4]

Two from: Fast and efficient Small sample volume Decreased cost Increased separation efficiency

f) Describe two applications of capillary zone electrophoresis in the clinical laboratory [2]

Two from: Serum proteins Carbohydrate deficient transferrin (CDT) DNA Amino acids




Topic area: Electrophoresis Question no: 2

Electorphoresis is a common technique utilised in the clinical laboratory for a wide range of applications.

a) Define the principles behind

electrophoretic separation [4] Process by which molecules can be separated according to size and electrical charge by applying an electrical current [2]. Each molecule travels through the medium at a different rate depending on its electrical charge and molecular size [2]

b) State two different mediums used in electrophoresis [2]

Cellulose acetate Agarose gel

c) State two related electrophoretic techniques [2]

Two from: Isoelectric focusing Isotachophoresis Capillary zone electrophoresis

d) List two stains commonly used to visualise bands of interest [4]

Two from: Coomasie Blue Ponceau S Silver stain Amido Black Ethidium bromide

e) Name two applications of electrophoresis in the clinical laboratory [4]

Two from: Alkaline phosphatase isoenzymes Urine and serum proteins Alpha 1 Antitrypsin phenotyping

f) State two advantages of capillary zone electrophoresis over standard electrophoretic separation techniques [4]

Two from: Fast and efficient Small sample volume Decreased cost Increased separation efficiency




Topic area: Endocrinology Question no: 1 A woman aged 50y visits her GP complaining that she feels tired all the time, that she is experiencing symptoms suggestive of the menopause and that her periods have become intermittent. The GP takes blood and tells her that he is going to assess both the likelihood that she is in transition to menopause and her thyroid function status. Thyroid function test results are FT4 14pmol/L (9-25) and TSH 8.5mU/L (0.40-4.50) a) Which single biochemical test is most

useful in assessing menopausal transition? [2]

Follicle stimulating hormone (FSH)

b) What is this biochemical pattern of thyroid function tests called? [2]

Subclinical (or borderline) hypothyroidism

c) What strategy would you advise the GP to pursue to follow up the patient and decide if/when to commence thyroxine therapy? [6]

Repeat TFT to confirm pattern [1] (3 to 6 months) [1] Measure TPOAb [1] to determine frequency of future TFT testing [1] Treat when TSH >10mU/L [1]or when symptoms develop further [1]

d) Describe the TSH levels typically found in patients with primary hypothyroidism, secondary hypothyroidism and hyperthyroidism [6]

Hypothyroidism – raised TSH [2] Secondary Hypothyroidism – low normal TSH [2] (normal 1 mark) Hyperthyroidism – undetectable TSH (low 1 mark)

e) What is the most important biochemical objective of thyroxine replacement therapy in primary hypothyroidism? [2]

Normalization of serum TSH

f) When assessing thyroid replacement in primary hypothyroidism, what is the minimum acceptable period between biochemical tests of thyroid? [2]

6-8 weeks




Topic area: Endocrinology Question no: 2 The hormones of the adrenal cortex are essential for survival a) Name the two major hormones

produced in the adrenal cortex. [2] Cortisol Aldosterone

b) Summarise the main physiological actions of each of these hormones [4]

Cortisol: Maintains plasma glucose during fasting; increases gluconeogenesis; stimulates lipolysis [3] Aldosterone: Stimulates tubular reabsorption of sodium [1]

c) Give two clinical symptoms or signs for acute and for chronic adrenal insufficiency. [4]

Acute –two from: shock, nausea/vomiting, epigastric pain, postural hypotension Chronic – two from: tiredness, weakness, weight loss, pigmentation (primary disease)

d) List two causes of primary adrenal insufficiency? [2]

Two from: Autoimmune, tuberculosis, sarcoidosis, haemachromatosis, congenital defects, adrenalectomy

e) List two causes of secondary adrenal insufficiency? [2]

Two from: Iatrogenic (exogenous steroid), hypopituitarism, post-pituitary surgery

f) Name three laboratory tests that are used in the diagnosis of glucocorticoid deficiency? [6]

Serum cortisol response to Synacthen Basal plasma ACTH Serum cortisol response to insulin induced hypoglycaemia (allow serum ACTH and cortisol response to CRF)




Topic area: Endocrinology Question no: 3

A 55-year old Caucasian lady is seen by her GP for tiredness. Her thyroid function results are as follows:

• Free T4 12 pmol/L (7.5 – 21.0) • TSH 9 mU/L (0.3 – 4.0)

a) How would you define these results? [2] Subclinical (or borderline)

hypothyroidism

b) List two risk factors for developing hypothyroidism? [4]

Two from: Female Family history Presence of autoimmune disease Drug treatment (or specific drug inc. amiodarone and anti-thyroid therapy)

c) What autoantibody is of value in further investigation of this case? [2]

Thyroid peroxidise (TPO)

d) Give two other diseases that might be associated with these results [4]

Two from: Addison’s Disease Pernicious anaemia Diabetes mellitus Autoimmune hepatitis

e) Describe the probable mechanism behind this condition [4]

Antibodies against TPO are found in most (95% of ) patients with autoimmune hypothyroidism [2]. TPO plays a critical role in thyroid hormone synthesis and antibodies therefore interfere with hormone production [1]. It is also likely that TPO plays a pathogenic role in the destruction of thyrocytes [1].

f) When should treatment start in this patient? [4]

Thyroxine therapy should be started if TSH rises above 10mU/L [2] or if symptomatic of hypothyroidism [2]





A 23-year old lady presents to her GP complaining of anxiety and has recently suffered a family bereavement. Her thyroid function test results are as follows:

• Free T4 80 pmol/L (7.5 – 21.0) • Free T3 40 pmol/L (3.8 – 6.0) • TSH < 0.1 mU/L (0.3 – 4.0)

a) What is the most likely diagnosis based

on these results? [2] Thyrotoxicosis (or hyperthyroidism)

b) List four causes or triggers for this condition? [4]

Two from: Anxiety/stress Iodine overload Autoimmune disease Infection Drugs e.g. amiodarone

c) Give two further investigations you would recommend [2]

Autoantibodies against thyroid peroxidase Radioiostope scan using 131Iodine

d) List four diseases might be associated with this condition[4]

Addison’s Disease Diabetes Mellitus Pernicious anaemia Autoimmune hepatitis (allow other recognised autoimmune)

e) Describe the possible mechanism behind the commonest cause of this condition [4]

Hyperthyroidism of Grave’s disease is mediated via the effect of IgG class autoantibodies [1] that bind to TSH receptor [1]. This causes an increase in intracellular concentrations of AMP [1] and the consequent synthesis and release of thyroid hormones [1].

f) List the possible treatment options [4] Carbimazole Propylthiouracil (PTU) Radioiodine Thyroidectomy




Topic area: Endocrinology Question no: 5 The most common cause of congenital adrenal hyperplasia (CAH) is a deficiency of the enzyme 21-hydroxylase. a) What is the gene which is affected in

this condition? [2]

CYP21A2 or CYP21A or CYP21

b) Describe the mechanism of the adrenal hyperplasia in this condition. [6]

Deficiency in 21-hydroxylase results in a block in cortisol synthesis [2]. This leads to a compensatory increase in ACTH release [2]. ACTH stimulates steroid synthesis to the point of enzyme block, resulting in adrenal hyperplasia [2].

c) Why are do some people with 21-hydroxylase deficiency get salt-wasting and hypotension while others do not? [4]

In some patients the enzyme is deficient only in the zona fasiculta. In others the defect extends to the zona glomerulosa, resulting in aldosterone deficiency and thus salt-wasting and hypotension.

d) Which steroid would be measured as a first line screen in a neonate suspected of having classical CAH? [2]

17-hydroxyprogesterone or 17-OHP

e) What physical sign would be present at birth in a girl with severe CAH? [2]

Ambiguous genitalia

f) 11β-hydroxylase deficiency results in a form of CAH with salt-retention and hypertension. What is the basis for this? [4]

11β-hydroxylase deficiency results in a build-up of deoxycorticosterone which has aldosterone like activity, thus resulting in salt-retention and hypertension.





With regard to the investigation of infertile couples

a) What test is used to confirm ovulation in

females, and when should the sample be taken? [4]

Progesterone [2]. Mid-luteal phase (allow day 21 sample or seven days before period is due) [2]

b) List 2 causes of amenorrhoea in the female [2]

Two from: Primary ovarian failure (e.g. Turner’s syndrome, autoimmune), gonadotrophic disorders (e.g. hyperprolactinaemia, pituitary disease), weight loss/ excessive exercise, chronic illness, PCOS, late-onset CAH, ovarian tumour Menopause, pregnancy (allow any other reasonable)

c) What metabolic complication is associated with PCOS? [2]

Insulin resistance (allow dyslipidaemia or hyperglycaemia)

d) Uterine dysfunction is a rare cause of amenorrhoea – what test is used in its investigation? [4]

Progestogen challenge test

e) List 2 causes of male infertility [4] Structural abnormalities (e.g. varicocele, ductal, prostate), endocrine disorders (e.g. Kallman’s, hyperprolactinaemia), testicular (e.g. Klinefelter’s), sperm antibodies, sexual dysfunction

f) Name 4 laboratory investigations that should be carried out in the male being investigated for infertility? [4]

Semen analysis, gonadotrophins, testosterone, prolactin (allow SHBG)




Topic area: Endocrinology Question no: 7 A male patient is found to have a serum prolactin concentration of 843mIU/L, a macroprolactin is added by the Clinical Biochemist. a) What is macroprolactin? [2] High molecular weight forms of prolactin

b) Why is it important to screen for

macroprolactin? [6] Macroprolactin is biologically inactive [2] Macroprolacin cross reacts with prolactin assays giving false positive results [2] Stop unnecessary investigation of patients with high prolactin levels [2]

c) Name the common method for macroprolactin detection? [2]

PEG precipitation

d) Name the definitive method for macroprolactin detection? [4]

Gel filtration chromatography

e) What immune disease has been shown to affect macroprolactin estimates? [2]

HIV

f) State two other possible reasons, apart from pituitary disease, for this prolactin result [4]

Two from: Stress response Antipsychotic drug Antiemetic drug Assay interference





A 25 year old woman was referred to an endocrinologist for investigation of oligomenorrhoea, hirstuism and easy bruising. The endocrinologist noted increased abdominal fat and raised blood pressure. A diagnosis of Cushing’s syndrome was suspected.

a) State two possible causes of increased

cortisol secretion. [2] Stress, Obesity, Depression Excess ACTH production: Cushings disease, ectopic ACTH due to malignancy Excess cortisol : Adrenal tumour, alcohol, steroid therapy Excess cortisol binding globulin: Oestrogen therapy, Oral contraceptive, pregnancy

b) State two biochemical tests that can be used to screen for Cushing’s syndrome. [2]

24 hour urinary cortisol Early morning urine cortisol (x3) Dexamethasone suppression test

c) What is meant by the term ‘circadian rhythm’ and what happens to this in Cushing’s syndrome. [4]

Circadian rhythm relates to the daily variation in the secretion of an analyte. Circadian rhythm in cushing’s syndrome is lost. Cortisol is secreted continuously.

d) State two causes of pseudo-cushings. [2] Depression Alcohol Stress

e) Describe the high dose dexamethasone suppression test and the cortisol result you would expect if the tumour originates in the pituitary. [6]

2mg of dexamethasone given 6 hourly for 48 hours. Cortisol taken at baseline, 9am on day 1 and 9 am on day 2. Some candidates may describe the 8mg overnight test which is also acceptable. In this test, basal cortisol is taken at 9am. 8mg dex given at 11pm and blood taken at 9am the following morning. In pituitary dependent Cushing’s the plasma cortisol should suppress to below 50% of the basal level.

f) Having identified a patient with Cushing’s syndrome name two non-biochemical investigations that are available to aid the diagnosis [4]

Inferior petrosal sinus sampling CT scan MRI




Topic area: Endocrinology Question no: 9 A one-year old girl is seen in A&E. She has ambiguous genitalia and abnormal serum electrolytes. Previously undiagnosed congenital adrenal hyperplasia (CAH) is suspected. a) Which enzyme in the steroid pathway is

defective in the majority of cases of CAH in the UK? [2]

21α-hydroxylase

b) Why are the electrolytes affected in this condition and what are the electrolyte disturbances commonly found? [4]

Inadequate secretion of aldosterone [2] resulting in potassium retention (high potassium) [1] and sodium excretion (low sodium) [1].

c) State two other enzyme deficiencies which cause CAH. [2]

Two from: 11β-hydroxylase deficiency, 3β hydroxydehydrogenase deficiency, 17α-hydroxylase deficiency, StAR protein deficiency

d) What biochemical blood test is used to aid the diagnosis of CAH and may be used for neonatal screening for the condition. State one cause of false positive results? [4]

17 hydroxyprogesterone [2] One from: • Maternal contribution if blood taken

before day 3 of life • Stress • Prematurity

e) What is the cause of late onset female CAH? [2] State two clinical effects of this condition [4]

Late onset CAH is caused by alleles that result in mild degrees of hyperandrogenism. Two from • Mild androgen effects in young

women • hirsutism • acne • anovulation (which in turn can cause

infertility). • Testosterone levels in these woman

may be mildly elevated. • Symptoms similar to PCOS •

f) Genetically, what is the pattern of inheritance for this condition? [2]

Autosomal recessive




Topic area: Endocrinology Question no: 10 Maintenance of normal potassium levels is essential to the life of cells. The distribution of potassium is such that 90% of total body potassium is intracellular and only 2% is extracellular. a) Name the pump that maintains this

intracellular to extracellular potassium ratio [2]

Na+K+ ATPase

b) Name the major route of potassium output and the adrenal hormone involved in its regulation [2]

-Renal excretion -Aldosterone

c) Name three other physiological factors that modulate potassium excretion [6]

Three from: -Potassium concentration -Sodium delivery- flow rate -ADH -Chloride delivery -pH

d) Name the syndrome of primary hyperaldosteronism [2]

Conn’s syndrome

e) Explain the effects of primary hyperaldosteronism on potassium concentration [4]

Hypokalaemia is due to increased sodium retention as a result of the excess aldosterone, which acts on the distal tubule to produce a net increase in sodium absorption [2]. As sodium reabsorption increases, potassium secretion is simultaneously increased, largely to maintain electroneutrality [2].

f) Describe 2 adrenal causes of primary aldosteronism [4]

Two from: -Aldosterone producing adrenal adenoma -Idiopathic adrenal hyperplasia (Hyperplasia of aldosterone producing cells in both adrenals) - Glucocorticoid-remediable aldosteronism




Topic area: Enzymology Question no: 1

A 36-year old woman experiences prolonged apnoea following surgery. Her Doctor is concerned that she may be sensitive to muscle relaxants and collects a sample for Cholinesterase phenotyping the following day.

a) What enzyme forms the basis of cholinesterase phenotyping, and what other form of this enzyme is there? [2]

Phenotyping for butyrylcholinesterase Other form is acetylcholinesterase

b) What two factors are important in determining the patient’s level of risk? [2]

Phenotype and enzyme activity

c) List three reasons that could potentially cause a secondary increase in a person’s risk of sensitivity to muscle relaxants. [6]

Three from: Renal failure Malnutrition Certain Malignancies Pregnancy Neostigmine OCP/HRT Organophosphates Carbamates Liver disease

d) Describe the basis of the phenotyping assay. [4]

The disappearance of the substrate is measured using a spectrophotometer [1]. Inhibitors of cholinesterase activity are incubated with the sample [1]. The ‘normal’ cholinesterase enzyme will be inhibited by these inhibitors reducing in reduced substrate conversion [1]. The percentage inhibition of the enzyme by each of the inhibitors allows assignment of a particular phenotype [1].

e) Why did the doctor wait until the following day to collect the sample? [2]

You need to wait for the drug to be cleared from the body [1]. If the drug is present when the analysis is performed this can lead to erroneous activity and inhibitor numbers [1].

f) The patient is told that she has an UA phenotype and family studies are recommended. She has a five-year old daughter who is found to have a ’Usual’ phenotype, what advice would you give to the requesting clinician and why? [4]

To retest the child after puberty [1]. Children have higher activity levels than adults [1]. Adult levels are reached by puberty [1]. A ‘usual’ phenotype does not exclude the presence of a quantitative variant [1].




Topic area: Gas transport and H+ metabolism Question no: 1 An elderly man was admitted to hospital by his GP for exacerbation of his COPD and LVF. He was treated on the ward with bendrofluazide and iv furosemide where it was noted that he had developed a metabolic alkalosis. a) State 2 risk factors for developing

COPD [4] Two from: Smoking; environmental exposure to toxins; alpha 1 antitrypsin deficiency

b) What biochemical findings indicate a metabolic alkalosis? [2]

Reduced H+ or high pH (1) Increased plasma bicarbonate (1)

c) State 2 causes of metabolic alkalosis. [2]

Two from: Excess vomiting, hypokalaemia, mineralocorticoid excess, excessive consumption of antacids/milk

d) What is likely to have precipitated this patient developing a metabolic alkalosis? [2]

Hypokalaemia from diuretic therapy

e) What will the pH of his urine be and why? [6]

Paradoxical acid urine. K+ depletion leads to HCO3 reabsorption in proximal tubule and increased NH4+ production – i.e. net increase in urine H+ excretion

f) Outline the principles of the measurement of H+. [4]

Ion selective electrode measures the difference in potential of the unknown solution compared to the reference method.




Topic area: Gas transport and H+ metabolism Question no: 2 The interpretation of blood gas measurements can be challenging. Assume the following reference ranges: H+ 38-43 nmol/L pCO2 4.6-6.0 kPa Serum bicarbonate 21-28 mmol/L. a) What kind of acid-based disorder would

be associated with the following results H+ 89nmol/L; pCO2 2.8kPa; Bicarbonate 11 mmol/L. [4]

Uncompensated metabolic acidosis

b) Suggest a clinical condition that could explain the results in a). [2]

Cardiac arrest

c) What kind of acid-base disorder would be associated with the following results H+ 26 nmol/L; pCO2 2.8kPa; Bicarbonate 20 mmol/L. [4]

Uncompensated respiratory alkalosis

d) Suggest a clinical condition that could explain the results in c) [2]

Hysterical over breathing

e) What is the Henderson Hasselbach equation? [4]

pH = pKa + log [Base] / [Acid] – log[H+]= - logKa – log[Acid] / [Base]

f) What is the anion gap and give one example of how it could be useful? [4]

Anion Gap = ([Na] + [K]) - ([Cl] + [HCO3]) Useful for detecting unmeasured anions. E.g. increased anion gap in ketoacidosis, lactic acidosis, salicylate poisoning etc




Topic area: Genetics and molecular biology Question no: 1 In the last 20 years, molecular genetics and diagnostics have been improved due to developments of PCR. a) What does PCR stand for? [2] Polymerase chain reaction

b) What are the four critical components

(ingredients) needed for a PCR to be carried out? [4]

Thermostable DNA polymerase, Nucleotides of each base (dNTPs) Target DNA sequence Primers (complementary oligonucleotides)

c) What is the purpose of including a negative control in a PCR run, and how is it created? [2]

To check for contamination All ingredients except target DNA

d) What is reverse transcriptase? Name a use for this. [4]

The enzyme that converts single stranded RNA into double stranded DNA. [2] One from: RT-PCR to amplify DNA from RNA. Creation of cDNA libraries from mRNA. Detection of retroviruses.

e) What does SNP stand for? [2] Single nucleotide polymorphism

f) Explain the meanings of the terms’mutation’ and ‘polymorphism’. [6]

A mutation is any change to the wild-type DNA structure due to a base substitution, deletion, translocation etc. [3] A polymorphism is a common variation in DNA structure found in at least 1% of the population. [3]




Topic area: Genetics and molecular biology Question no: 2 Hereditary Haemochromatosis is normally an autosomal recessive condition due to mutations in a gene known as the HFE gene. a) Which ethnic population has the highest

prevalence of predisposing genotype? [2]

Caucasian of Northern European origin

b) What diagnostic tests are carried out? [4]

Plasma iron, ferritin and transferrin saturation [2]. HFE genotyping [1]. Liver biopsy [1].

c) What is the classic triad of signs when the condition is expressed? [6]

Liver disease (hepatomegaly) Hyperglycaemia Pigmented skin

d) What is the basis of treatment of this condition? [2]

Venesection to normalise indicators of iron status

e) Both parents have symptomatic haemachromatosis. What are the chances of the girl child (age 16) expressing the condition? Or the older son (age 22)?. Explain your reasoning. [4]

Although both children will be homozygous the daughter is unlikely to express disease at this age [1], son more likely to express disease [1] but chances still relatively low. Disease expression generally low [1], with males more likely than females [1]

f) A mutation associated with hereditary haemochromatosis is referred to as C282Y. What does this terminology define? [2]

Single point polymorphism at position 282 with cysteine being replaced by tyrosine




Topic area: Immunochemical techniques and radioisotopes Question no: 1 Two-site immunometric assays are used for the measurement of a wide range of biochemical analytes a) What does ‘two-site’ mean in the

context of an immunometric assay? [2] Use of two antibodies

b) In a typical two-site immunometric assay: Are the antibodies present in excess or are concentrations limiting? [2] Is the assay design competitive or non-competitive? [2]

Excess [2] Non-competitive [2]

c) List three benefits to assay performance arising from the two-site immunometric assay compared to the single-site immunoassay? [6]

Three from: Better minimum detection limit (more sensitive) Wider working range Quicker to perform Readily adaptable to automated analysers Less susceptible to interference

d) Describe the relationship between analyte concentration and signal in an immunometric assay and indicate why in general this assay format has greater sensitivity than a competitive immunoassay

Signal increases in proportion to analyte concentration [2] Higher sensitivity because higher signal to noise ratio [2]

e) Why does the number of wash steps used in a two-site immunometric assay influence the minimum detection limit of the assay? [2]

Reduces signal to noise ratio

f) Why does the two-site immunometric assay design not lend itself to the measurement of steroid hormones (e.g. cortisol)? [2]

Steroid not large enough to have two separate binding sites




Topic area: Inherited metabolic disorders Question no: 1 A 4-day old baby boy presents with poor feeding, vomiting, and reduced level of consciousness. He was born at term and was initially well. You are duty biochemist and receive a phone call from paediatric admissions wanting to add on ammonia to the U&Es and LFTs already sent to the laboratory. a) Can the ammonia be added on? Explain

your answer [4] No [2] Requires specific collection procedure [2] (Paediatric lithium heparin tube and transfer to lab on ice)

b) State 2 other EMERGENCY tests that you would recommend? [2]

Two from: Blood gases Plasma glucose Lactate

c) State two further crisis samples that should be collected to investigate for a metabolic disorder [2]

Two from: urine organic acids plasma amino acids blood spot or plasma acylcarnitines blood for galactose-1-phosphate uridyl transferase

d) Name three groups of metabolic disorders that may result in a raised ammonia level [6].

Urea cycle defects Organic acidurias Fatty acid oxidation defects

e) What acid-base disorder would you expect to see if the child had a urea cycle defect? [2]

Respiratory alkalosis

f) What is the most common urea cycle disorder, and what is its mode of inheritance? [4]

Ornithine transcarbamoylase deficiency (OTC) [2]. X-linked [2]




Topic area: Inherited metabolic disorders Question no: 2

A 9-day old term baby boy, born to healthy parents, presented to A&E floppy, with a history of poor feeding. On admission both ammonia and lactate were normal. A urine specimen showed gross ketosis and had a sweet odour. A diagnosis of Maple Syrup Urine Disease is considered.

a) What is the enzyme defect in Maple

Syrup [2] Deficiency in 2-ketoacyl-Co A dehydrogenase.

b) What findings would you expect to see on an amino acid profile [6]

Elevated branched chain amino acids [3] leucine [1], isoleucine [1] and valine [1].

c) What further analyses would you perform to confirm the diagnosis [4]

Quantitative amino acids [2] Detection of alloisoleucine [2]

d) What is the treatment regime for this disorder during the acute phase [4]

Treat metabolic de-compensation [1] Reduce branched chain amino acids [1]. Induce anabolism and protein synthesis via high energy feed glucose, insulin and lipids [1]. Dialysis [1]

e) What is the principle neurotoxin [2] Leucine

f) What is the mode of inheritance and the likelihood of his subsequent siblings having the same condition [2]

Autosomal recessive disorder [1] 1:4 (25%) [1]




Topic area: Inherited metabolic disorders Question no: 3 A 13-year old boy has become increasingly drowsy and ataxic. On admission his UE, LFT are unremarkable, but his ammonia is 550 umol/l with a markedly increased urinary orotic acid. a) What is the most likely diagnosis? [2] Ornithine transcarbamylase deficiency

b) What findings would you expect in an

amino acid profile? [4] Increased glutamine and alanine [2] Decreased ornithine and citrulline and absent arginosuccinate [2]

c) How would you confirm the diagnosis? [2]

Enzyme analysis

d) State the mode of inheritance of this condition and indicate the risk that his female cousin is a carrier who has previously been entirely well. [4]

Condition is X-linked [2]. If there is a common grandfather [1], risk of carriage is 1 in 4. [1]

e) What biochemical test may help address this? [4]

Allopurinol loading test

f) What implications are there for this cousin and her baby, should she become pregnant? [4]

Cousin could become acutely encephalopathic after delivery – monitoring required [2]. 1 in 8 chance that offspring will be affected, if male, within first two weeks of life [2].




Topic area: Inherited metabolic disorders Question no: 4

A 25 year old female presents to A&E with severe abdominal pain and peripheral neuropathy. Her father has previously been diagnosed with acute intermittent porphyria (AIP).

a) A simple urine test for which porphyrin

precursor should be available to screen for acute porphyrias? [2]

Porphobilinogen

b) What enzyme is deficient in AIP and what reaction does it catalyze. [4]

PBG deaminase/HMB synthase [2] Porphobilinogen (PBG) Hydroxymethylbilane [2]

c) Name the 2 other most common acute porphyrias in the UK. [4]

Hereditary coproporphyria [2] Variegate porphyria [2]

d) How could AIP be distinguished from the other acute porphyrias biochemically? [6]

Using plasma and faecal porphyrins [2] HCP has increased faecal porphyrin excretion due to increased coproporphyrin III excretion. AIP faecal excretion is normal or only very mildly raised [2] VP has a plasma porphyrin fluorescence emission maximum at 625-628 nm. The emission maxima for both AIP and HCP is 615-620 nm [2].

e) State 2 common precipitants of an acute attack in young women. [2]

2 of: Pregnancy, premenstrual, infection, stress, starvation, drugs, alcohol

f) What is the rationale for prescribing haem arginate during an acute attack? [2]

Supplies haem which has a negative feedback effect and down regulates the activity of ALA synthase.




Topic area: Inherited metabolic disorders Question no: 5 A female patient age 32 years presented at A&E with acute abdominal pain, nausea and vomiting. No obvious cause could be found for the symptoms. Her mother was said to have been diagnosed with porphyria some years ago a) Of the various types of porphyria which

is the likeliest to cause this type of presentation? [2]

Acute intermittent porphyria

b) What biochemical test is useful in the initial investigation of this case? [2]

Urine porphobilinogen (PBG). A normal PBG during an acute episode excludes porphyria as cause.

c) Name two precipitating factors that can cause the development of these symptoms? [4]

Two from: Drugs (ethanol, barbiturates, anticonvulsants etc.) Hormones (especially oestrogen in premenopausal women) Dietary restriction Inter-current illness

d) What is the nature of the inheritance of this type of porphyria? [2]

Autosomal dominant

e) How should studies be carried out on the patient’s family? [4]

EDTA blood from affected relative and family members sent to reference laboratory for measurement of red cell PBG deaminase and for detection of mutation present in affected individual

f) What biochemical tests should be available locally, and when should sample be sent to a reference laboratory? [6]

Locally: urinary PBG and total porphyrin, faecal total porphyrin, serum porphyrin scanning. Urinary PBG may be required on urgent basis. Reference laboratory: all additional definitive tests including molecular diagnostics (This will depend on the candidates laboratory experience and as long as all analysis is mentioned, full marks should be allocated)




Topic area: Laboratory instrumentation Question no: 1

A consultant nephrologist telephones you while duty biochemist, concerned that the bicarbonate results being produced by your lab are lower than normal.

a) What two pieces of lab data would you

examine to determine if this was the case? [4]

Internal quality control results Latest EQA scheme return

b) Suggest two actions you could take if the assay was not in control [4]

Two from: Change reagents Check QC material in date Re-calibrate Use alternative method

c) The UK NEQAS return for the assay shows a poor ‘C score’. What does ‘C score’ mean? [2]

Consistency of bias

d) The assay uses a “one point calibration”. What is the second point used? [2]

Zero

e) State two acid-base disorders in which bicarbonate may be low. [4]

Metabolic acidosis Respiratory alkalosis

f) What would you advise the nephrologist to do if the assay was not in control? [4]

Do not act on affected results [1] Ensure incorrect results are marked as such in patient record [1] Repeat samples if assay error can be rectified immediately [1] If urgent suggest use results from blood gas analyser [1]




Topic area: Laboratory instrumentation Question no: 2 The UK Departments of Health have determined that all medical laboratories should be enrolled with an approved accreditation body.

a) Most NHS laboratories choose to be

enrolled with CPA. What is the full name of the organization abbreviated to CPA? [2]

Clinical Pathology Accreditation UK Ltd

b) What is the timetable used by CPA for full accreditation assessments and surveillance visits? [4]

Full assessments every 4 years Surveillance visits in the intervening 2 years

c) The CPA standards for laboratory accreditation are based on which international standard for the accreditation of medical laboratories? [2]

ISO 15189

d) The CPA standards place great emphasis on the laboratory service meeting the needs and requirements of its users. List four ways in which a laboratory may demonstrate that it is complying with this standard. [4]

Four from: User satisfaction surveys, Clinical audit of selected areas of service Input to and compliance with best practice guidelines, Grand Rounds, Meetings with users, Interactive websites Email suggestions box

e) Quality management is central to CPA laboratory accreditation. List three features of an effective quality management system. [6]

Three from: Quality policy; Quality manager; Quality plans and objectives; Annual management review; Document control system; planned programme of audits (Allow other relevant)

f) Name one other body approved for accreditation of UK medical laboratories. [2]

UK Accreditation Service (UKAS)




Topic area: Laboratory instrumentation Question no: 3 An understanding of evidence-based medicine (EBM) is fast becoming an essential requirement for the clinical biochemist as we move towards an era of knowledge management. One component of EBM is the level of research evidence from the literature. a) Describe a meta-analysis. [4] Statistical aggregation of data [2] from a

set of comparable studies [2] b) Describe a systematic review. [4] A review based on the selection [1] and

critical appraisal [1] of relevant [1] research to answer a specific question [1]

c) Describe a cohort study [4] A research study that compares a particular outcome in groups of individuals [2] that are alike in many ways but differ in a certain characteristic [2]

d) Which of the above a) to c) would yield the lowest level of research evidence? [2]

c) Cohort study

e) The Cochrane Library has an important role to play in EBM. What is that role? [2]

Source of evidence-based systematic reviews

f) Apart from research evidence describe two other factors that should be taken into account when practicing EBM [4]

Clinical experience Patient values




Topic area: Laboratory methods Question no: 1 Dipsticks can be used at the point-of-care to test for a number of analytes in urine.

a) Name the two enzymes used in the urine

dipstick test for glucose. [4]

Glucose oxidase and peroxidise.

b) Name two substances which may interfere with the urine dipstick test for glucose. [4]

Reducing agents (e.g. ascorbic acid) and ketones.

c) Explain why the urine dipstick test for glucose is a poor screening test for diabetes mellitus. [4]

Plasma glucose level must be above the renal threshold (~10mmol/L) before glucose will pass into the urine. This makes urine glucose analysis an insensitive test for raised plasma glucose levels.

d) Name 2 physiological states which may result in a positive urine dipstick test for ketones. [4]

Pregnancy, prolonged fasting, low carbohydrate diet.

e) What is the reaction used in the urine dipstick test for bilirubin. [2]

Bilirubin + Diazo salt → Azobilirubin

f) A urine dipstick shows bilirubin ++ and urobilinogen negative. Would this picture be associated with biliary obstruction or haemolytic anaemia? [2]

Biliary obstruction




Topic area: Laboratory methods Question no: 2 The most common methods for bilirubin measurement use diazo reagents a) Which fraction of bilirubin reacts with

diazo in the absence of an accelerator? [2]

Conjugated/direct

b) Name one accelerator that can be used in the diazo reaction [2]

One from: Alcohol (methanol/ethanol) Caffeine Urea Surfactant/detergent

c) What would be your response, if asked to add a bilirubin measurement to an existing 3 day old sample Explain why and what you would recommend [6]

Would not add test [2] Bilirubin is light sensitive [2] Suggest fresh sample [2]

d) List 2 of the 4 bilirubin fractions in plasma [4]

2 from: Unconjugated bilirubin (alpha) Monoglucuronide conjugated bilirubin (beta) Diglucuronide conjugated bilirubin (gamma) Bilirubin bound to albumin (delta)

e) Which common interferent is the direct spectrophotometry method for bilirubin sensitive to? [2]

Haemolysis

f) Explain why use of a bilirubinometer should be restricted to newborns [4]

May be pigments present in serum from older children and adults [2], which interfere with measurement [2]




Topic area: Laboratory methods Question no: 3

60 year old man on admission to A&E has the following test results. Sodium 130 mmol/L, potassium 5.6 mmol/L, urea 35.0 mmol/L, creatinine 104 µmol/L Bilirubin 728 µmol/L, ALP 402 U/L, ALT 241 U/L, GGT 987 U/L The comment attached to the results was: NB-Icteric sample.

a) Which creatinine method is affected by

icteric samples? [2] Jaffe

b) What effects do icteric samples have on the creatinine result? [2]

May lower result

c) Name and outline a creatinine method that overcomes interference from bilirubin and state how it achieves this [4]

O’Leary: Creatinine+Picrate+Ferricynaide (under alkali conditions) [2] goes to chromagen, ferricynanide oxidises bilirubin at start of the reaction [2] or Enzymatic methods [2] as they don’t record wavelength in visible spectrum that bilirubin interferes with [2]

d) State 2 other possible interferences in serum creatinine measurement [2]

Two from: Ascorbic acid, protein, acetone, acetoacetate, pyruvate, guanidine, cephalosporins

e) Explain briefly how the colourimetric creatinine assay can be adapted to minimise these the effect of these interferants. [6]

Development of kinetic assay [2], and selecting the correct reading interval after fast reacting chromagens [2] and before slow reacting chromagens [2] have reacted

f) State two other possible clinical causes of the raised urea in this case? [4]

GI bleed, dehydration




Topic area: Laboratory methods Question no: 4 A serum sample from a patient who had multiple myeloma was received from a GP surgery. Urea and electrolytes results were as follows: Sodium 110 mmol/L Potassium 3.2 mmol/L Chloride 105 mmol/L Urea 6 mmol/L Creatinine 80 µmol/L Sodium was initially measured indirectly using an ion selective electrode (ISE). Reanalysis by direct ISE generated a sodium result of 137 mmol/L. a) Name the phenomenon underlying the

differences between direct and indirect serum sodium results. [2]

Pseudohyponatraemia

b) State 2 biochemical abnormalities that may cause the discrepancies between the above serum sodium results. [2]

Hyperproteinaemia and hypertriglyceridaemia.

c) Other than direct ISE, what additional laboratory serum or plasma test is useful in the investigation/verification of such sodium results and how is this interpreted? [4]

Serum or plasma osmolality [2] Normal osmolality with low serum sodium by indirect ISE suggests pseudohyponatraemia [2]

d) Excluding gas sensing electrodes, name two types of membrane contained within an ISE. [4]

Two from: glass; solid state a.k.a. insoluble conductive inorganic salt; ion exchange a.k.a. chelating agent or polymer membrane. [2 marks for each]

e) Describe the principle of measurement of carbon dioxide by gas sensing ISE. [6]

Carbon dioxide diffuses from the test sample into the bicarbonate solution between the membrane and the electrode [2]. The pH of the bicarbonate buffer is a function of the partial pressure of CO2 [2]. Measures change in pH / change of hydrogen ion activity by means of a hydrogen ion selective membrane [2].

f) Define the term electrochemical cell. [2] Two electrodes / half cells connected by a conductor [1] through which electromotive force / current is generated by a chemical / redox reaction [1].





Sodium concentration in plasma or serum is commonly measured by ion-selective electrode (ISE) methods. In the presence of severe hyperlipidaemia or hyperproteinaemia, indirect ISE methods underestimate sodium concentration.

a) What is the name given to this effect?

[2] Accept electrolyte exclusion effect [2] or pseudohyponatraemia [2].

b) Briefly explain the basis of this effect. [6]

Volume occupied by solids in an aliquot of plasma is increased [2]. When the sample is diluted [2] the analyser wrongly assumes that the volume of plasma occupied by solids is normal [2].

c) Name one other method that can be used for sodium estimation that also demonstrates this effect. [2]

Flame photometry [2]

d) List two ways of overcoming this effect. [4]

Direct ion-selective electrode [2] Ultracentrifugation [1] with analysis of infranatant [1].

e) Hyperglycaemia causes a reduction in serum sodium concentration. Briefly explain the mechanism involved. [4]

Osmolality is increased [2] so water moves down the osmotic gradient to maintain osmotic balance [2].

f) Which drug can have a similar effect to that of hyperglycaemia on serum sodium concentration? [2]

Mannitol [2]





The IFCC has recently recommended that all HbA1c analysis be standardised to an IFCC recommended reference method.

a) What is meant by the term reference

method? [4] Highly accurate method that gives comparable results to the definitive method [2] and is used to define reference values [2].

b) Name the two reference methods recommended by IFCC for HbA1c standardisation [4]

HPLC-MS HPLC-Capillary electrophoresis

c) Explain how reference methods are used to standardise laboratory based routine methods?[4]

Reference standards assigned a value using reference method [2], these are used to assign calibrator values which can then be used routinely [2]

d) Define HbA1c[2] Haemoglobin irreversibly glycated at the N- terminal of the Beta chains

e) Name one method routinely used for HbA1c analysis[2]

Any from Ion- exchange HPLC Electrophoresis Immunoassay Affinity chromatography

f) What problems may the switch to IFCC standardisation cause and state two ways in which they will be overcome[4]

Different units and targets for HbA1c values may cause confusion for clinicians and patient effect patient control. [2] Education before change over [1] Reporting both results [1]




Topic area: Lipids Question no: 1 Lipid measurement has become increasingly important in characterising the cardiovascular risk as well as in the diagnosis and management of disorders of lipoprotein metabolism. a) What absorbance is used in the

measurement of cholesterol? [2] ~500nm

b) Name 2 enzymes that are most commonly used in the determination of cholesterol? [2]

Two from: - Cholesterol esterase - Cholesterol oxidase - Peroxidase

c) Name 2 common interferants in the measurement of cholesterol & describe how they cause interference. [6]

Two from: - Increased triglycerides- due to TG rich

particles that scatter light which is mis-read as absorbance

- Reducing substances (i.e. bilirubin, ascorbate)- compete with peroxidise enzyme for hydrogen peroxide and therefore, cause a decrease in the colour response

- Haemoglobin & Bilirubin- also have absorbance at ~500nm and so can increase the colour response. Severe haemolysis can also cause interference through dilution as cholesterol concentration is lower in the red blood cell than in serum

d) Give the Friedwald equation used to

calculate LDL-cholesterol concentration. [2]

LDL-cholesterol = total cholesterol – HDL-cholesterol – triglyceride/2.2

e) Name two circumstances when this equation must not be used [4]

Two from - Non fasting samples - Raised triglycerides (>4.5mmol/L) - Patients with type III

hyperlipoproteinaemia

f) What is the main problem with the LDL fraction when determined indirectly? [4]

- LDL consists of a population of particles which vary in size and lipid composition [2], therefore LDL has neither a unique molecular weight nor consistent cholesterol composition [2].




Topic area: Lipids Question no: 2

A 40-year-old man is referred to dermatology outpatients because he is suffering from yellow papules with erythematous bases on the buttocks and elbows. The dermatologist recognises the lesions as eruptive xanthomata and wonders if the man has type III hyperlipidaemia. Blood taken after an overnight fast shows:

• Cholesterol 7.9 mmol/L • Triglycerides 7.3 mmol/L

a) State one type of lipoprotein that is

increased in the serum of patients with this condition [2]

IDL (accept chylomicron remnants)

b) State one other clinical feature of this condition [2]

Any of Palmar crease xanthomas Lipaemia retinalis Pancreatitis Cardiovascular disease

c) Which apoprotein genotype is associated with this condition? [2]

Apo E-2/ E-2 genotype

d) State the first-line drug treatment for this type of hyperlipidaemia and the metabolic target of this drug [4]

Fibrate PPAR alpha receptor

e) Describe the characteristic appearance of serum lipoprotein electrophoresis in this condition [6]

Broad band [2] extending between the pre-β (VLDL) [2] and β (LDL) [2] regions

f) List two common causes of secondary hypertriglyceridaemia [4]

Any two of: Alcohol excess Diabetes mellitus Obesity Nephrotic syndrome Corticosteroids Oestrogens Progestogens




Topic area: Lipids Question no: 3

You are phoned by a nurse from the Coronary Care Unit who wishes to perform lipid investigations on a patient who suffered a myocardial infarction 3 days ago.

a) How long should the clinical team wait

before they can reliably assess the patient’s cholesterol status? [2]

2 months

b) Write down the Friedewald equation used to calculate LDL cholesterol in mmol/L. When is this equation not valid? [4]

LDL = total chol – (HDL + TG/2.19) [2] When TG > 4.5 mmol/L (2 marks) or In presence of chlyomicrons [2]

c) State two other methods for measuring LDL cholesterol [4]

Ultracentrifugation [2] Homogeneous/Direct/Enzymatic method [2]

d) What is the current Joint British Societies target for lowering LDL cholesterol in a patient who has had a myocardial infarction? [4]

To <2.0 mmol/L [2] or decrease by 30% [2]

e) State the predominant type of apoprotein present in LDL-cholesterol [2]

Apo B-100

f) State the first-line drug treatment in hypercholesterolaemia and name one other alternative drug treatment [4]

Statin [2] (accept HMG CoA reductase inhibitor) Alternatives Nicotinic acid derivative Fibrate Bile acid sequestrant




Topic area: Liver Question no: 1 A request for plasma copper is received for investigation of suspected Wilson Disease. The analysis is carried out using inductively couple plasma mass spectrometry (ICP-MS) and produces a low result of 5µmol/L (reference range: 10 to 22 µmol/L). a) What symptoms and signs might raise

the diagnostic possibility of Wilson Disease? [4]

Unexplained liver or neurological disease, especially in children / young adults. Other non-specific presentations. Kaiser-Fleischer rings (copper deposits in the cornea) may be present.

b) What is the reason for the low plasma copper concentration usually found in Wilson Disease? [2]

Low plasma caeruloplasmin due to defective synthesis

c) What other explanations might account for low plasma copper? [2]

Two from: Severe liver disease, Menke’s Disease, duodenal malabsorption, patients on zinc supplementation

d) Describe further diagnostic tests that would support a diagnosis of Wilson Disease. [4]

Four from: Low plasma caeruloplasmin, high urine copper, high urine copper excretion following oral penicillamine, high liver copper concentration, genetic screening

e) Describe the principle of ICP-MS and the benefits it offers over alternative techniques for measuring trace elements. [6]

Sample converted to aerosol by nebuliser and carried by inert gas (argon) into high energy plasma where temperatures of >5000C break chemical bonds and ionise resultant atoms. Positive ions separated by mass difference and detected by electron multiplier detector. [4] Benefits are ability to measure accurately to very low concentrations; simultaneous analysis of multiple elements. [2]

f) Explain how a co-existing systemic inflammatory condition could affect the plasma copper concentration? [2]

Caeruloplasmin is a positive acute phase reactant. Total copper may increase in a systematic inflammatory response.




Topic area: Liver Question no: 2

A GP patient has a persistently raised ALT result, greater than three times the upper limit of normal on several occasions over a 6 month period. The GP wishes to explore the possibility of hereditary haemochromatosis.

a) What reaction is catalysed by the ALT

enzyme? [4] L-alanine + 2-oxoglutarate ↔ Pyruvate + L-glutamate

b) Compare the use of AST with that of ALT as a liver function test in terms of sensitivity and specificity. [4]

ALT is more specific as AST is found in significant quantities in other tissues eg. heart, skeletal muscle, erythrocytes [2] AST is more sensitive to hepatic damage as liver cells contain more AST than ALT [2]

c) State 2 organs, other than the liver, which are commonly damaged by haemochromatosis. [2]

2 of; pancreas, heart, anterior pituitary, joints

d) Describe two other biochemical abnormalities that could be used to support a diagnosis of iron overload. [2]

2 of; Increased transferrin saturation Increased plasma ferritin Increased plasma iron concentration

e) Which gene is most commonly mutated in cases of haemochromatosis in the UK and what is the most common mutation? [4]

HFE gene [2] C282Y mutation [2]

f) Discuss when it is appropriate to screen for hereditary haemochromatosis using this mutation and why. [4]

Appropriate in family members of a known case with the mutation [2] C282Y has low penetrance and other mutations and other genes can cause haemochromatosis [2]




Topic area: Liver Question no: 3 At a private work related “Executive Health Screen” a 46 year old man was found to have a random serum cholesterol = 6.9mmol/L; triglyceride = 0.9mmol/L and HDL cholesterol = 1.2mmol/L. His U&Es were all within their respective reference intervals. His LFT were as follows. Bilirubin - 12µmol/L; ALT = 72 U/L (RI < 50); AST = 58 U/L (RI <35) Alk Phos = 186 U/L (RI 40-150); γGT = 177 U/L (RI < 90). He was reported that he was fit and healthy and totally asymptomatic. His father died at 62 and his brother at 23 from what was believed to be alcoholic liver disease, though he said that he did not believe these diagnoses. He said he was virtually teetotal and physical examination was unremarkable. His BMI = 24Kg/m2; BP 125/75mmHg : Pulse – sinus rhythm 60 min -1. a) Give two other routinely available

laboratory investigations could be used to help shed light on the veracity of his reported alcohol intake? [2]

Urate Macrocytosis (allow FBC indices)

b) The clinician requests that his plasma carbohydrate deficient transferrin is measured. What is the biological basis of this test? [2]

Alcohol inhibits the addition of sialic acid residues to the terminal end of the carbohydrate side chains of transferrin and other glycoproteins.

c) Briefly indicate the problems of using carbohydrate transferrin in the detection and monitoring of ethanol consumption in clinical practice. [6]

Analytical – standardisation [2] Specificity –genetic heterogeneity [2] Half-life [2]

d) On further investigation his C-reactive protein – 1mg/L and his α1-antitrypsin = 0.46g/L (RI = 1.1 – 2.1 g/L). Very briefly indicate the significance of these results. [2]

CRP indicates that he is not acutely inflamed thus the α1AT concentration has not been increased to higher than its basal level for this patient

e) You suspect that he may have partial α1AT deficiency. What is the most likely genotype he is likely to suffer from and very briefly outline the pathobiochemical consequences of this genotype? [6]

Pi MZ [2]. The Z mutation results in the failure to add a CHO side chain causing failure to export α1AT from the Golgi [2] leading to inclusion bodies and cirrhosis [2].

f) Briefly, giving your reasons, how would you recommend that he is followed up ‘biochemically’? [2]

α-foetoprotein for possible hepatocellular cancer as a complication of cirrhosis.





A 52 year old man has been found to have a persistently elevated ALT of 55-70 IU/l. Further investigations are obtained by the General Practitioner. Serum iron 45 umol/L (10 - 35) Serum TIBC 65 umol/L (35 – 70) Serum ferritin 1150 ug/L (25 – 330)

a) What is the most likely underlying

condition and, in the UK, which gene is affected in the most common form of the condition?[2]

Hereditary Haemochromatosis HFE gene

b) What is the mechanism of iron overload in this condition? [4]

Increased absorption of haem & non-haem iron [2]. Iron absorption not regulated by iron storage [1] and so accumulation occurs in many organs especially those with high levels of transferrin receptors [1]

c) List four other clinical manifestations of this condition. [4]

Any four of: Diabetes mellitus, arthropathy, slate grey skin, impotence, amenorrhea, cardiac enlargement, hypopituitarism, cardiac conduction defects

d) How can liver iron overload be assessed? [4]

Liver biopsy [2] – histological staining for iron (semi-quantitative) [1] or dry liver iron using atomic absorption (quantitative) [1]

e) What is the mainstay of treatment for this condition and how is the response to treatment assessed? [4]

Weekly therapeutic venesection until plasma ferritin falls to approx 50 ug/L. (500ml blood contains approx 250mg iron & 1ug./L ferritin is equivalent to about 8mg iron)

f) How should the patient’s siblings be screened for the condition? [2]

Genotyping





A 38 year old woman visits her GP requesting screening for haemochromatosis because she has been worried following a 54 year old male colleague being diagnosed with the condition.

a) What initial screening test should the

GP advise? [2] Serum Ferritin (or allow transferrin saturation) [2]

b)

Which gene is affected in genetic haemochromatosis and what is the mode of inheritance? [4]

HFE gene (haemochromatosis gene) [2] Autosomal recessive [2]

c) Name two organ systems potentially affected in genetic haemochromatosis and the clinical consequences that may result [4]

Two from: [2] Liver Pancreas Skin Myocardium Pituitary gland Joints Two from: [2] Hepatitis / liver failure / cirrhosis Diabetes mellitus Grey discoloration of skin Cardiomyopathy / heart failure Hypogonadism / tiredness / abnormal pituitary function tests Arthropathy / Joint pain

d) What is the treatment for hereditary haemochromatosis and how can the efficacy of this treatment be monitored? [4]

Vensesection [2] Serial serum ferritin [2]

e) List four causes of iron overload other than genetic haemochromatosis [4]

Anaemia with ineffective erthyropoeisis (accept specific named anaemia) Alcohol excess Inappropriate oral iron therapy Iron overdose Multiple blood transfusions Inappropriate parenteral iron therapy Inherited transferrin deficiency [1] each to a maximum [4]

f) Name an agent used for the elimination of iron from the body and what is its mode of action [2]

Desferrioxamine [1] Iron chelating agent [1]




Topic area: Metabolic response to disease Question no: 1

A 60 yr old male is in HDU three days after undergoing an elective aortic aneurysm repair operation.

a) Describe the changes in CRP concentration after major surgery [4]

CRP concentration increases by 4-6 hr peak 2-3 days and return to normal 7-10 days post surgery (if no infection occurs)

b) Explain the changes that occur in serum albumin concentration [2]

Albumin concentrations fall mainly due to increased leaky vasculature (allow 1 for acute phase response)

c) Thyroid function tests are often abnormal in acutely ill patients. What term is used to describe this? [2] Describe the changes in thyroid hormone metabolism [4]

Sick euthyroid syndrome/ Non-thyroidal illness [2] Decreased Total T3 and FT3 due to impaired tissue uptake of T4 [1] Decreased peripheral conversion of T4 to T3 [1] Changes in concentration of plasma binding proteins. [1] Increased plasma concentrations of free fatty acids which displace thyroid hormones from binding sites [1]

d) State two of the classical signs of the inflammatory response [2]

Two from: Capillary dilation, leucocyte infiltration, redness, heat, pain, swelling and loss of function

e) The inflammatory response causes changes in the concentration of certain proteins. List two proteins that increase and two that decrease during inflammation [4]

Increase: CRP, ∝-1 anti-trypsin, serum amyloid A, fibrinogen, haptoglobin, caeruplasmin, C3, C4 Decrease: Albumin, transferrin, IGF-1, transcortin

f) What acute phase protein can be used to differentiate infectious from non-infectious causes of inflammation [2]

Procalcitonin




Topic area: Neuromuscular system Question no: 1

It is important to detect Subarachnoid haemorrhage (SAH) in all patients with the condition. A CT-scan is only positive in 50% of patients within one week of the event. CSF bilirubin is used to help in the diagnosis of SAH.

a) For how long after the SAH event may a

CSF bilirubin remain positive? [2] 2 weeks

b) What special transport arrangements should be made for the CSF samples? [4]

Protect from light Do not use pneumatic tubes

c) Why should CSF taken before 2 hours not be analysed for CSF bilirubin? [4]

OxyHb is converted to bilirubin in a time-dependent manner. Minimum of 12 hours is required. May result in false negative results.

d) Briefly describe the analysis of the CSF bilirubin [6]

Perform zero order spectrophotometric scan on the supernatant between 350-600nm [2]. Use full-scale deflection of 0.1AU [2]. Measure NBA at 476nm [1] and NOA at between 410 and 418nm [1].

e) Why is it important to visually inspect the sample before analysis? [2]

To check for blood stained sample

f) What blood test should be requested at the same time, which may aid interpretation of the CSF bilirubin? [2]

Serum bilirubin and total protein




Topic area: Neuromuscular system Question no: 2 Subarachnoid haemorrhage (SAH), arterial bleeding into the subarachnoid space, is a difficult condition to diagnose clinically; diagnostic tests are relied on heavily in the confirmation or exclusion of the diagnosis. Spectrophotometric scanning of CSF for the presence of bilirubin and oxyhaemoglobin is a second line test used in the investigation of suspected SAH. a) What is the first-line test carried out

when SAH is suspected clinically? [2] Computerised tomography (CT) scan

b) What pre-analytical factors are important in ensuring reliable results from spectrophotometric scans for suspected SAH? [6]

Three from: Take samples at least 12 hours post onset of symptoms Send 3rd or 4th collection tube for scan Protect sample from light Avoid use of pneumatic tube

c) What are the absorption maxima that indicate the presence of

(a) bilirubin, and (b) oxyhaemoglobin [2]

(a) 476nm (allow 470 – 480) (b) 415nm (allow 410 – 420)

d) Is the presence of oxyhaemoglobin alone diagnostic of SAH? Explain your answer. [4]

No [2] Oxyhaemoglobin may be due to artefactual introduction of peripheral blood into the CSF e.g. due to a traumatic tap [2]

e) Give 2 instances where CSF bilirubin concentration may be increased, that are not due to SAH. [4]

Where CSF total protein concentration is raised Where serum bilirubin is increased

f) What is the effect of oxyhaemoglobin with a net absorbance of >0.1 AU on the detection of absorbance due to bilirubin [2]

May mask a small but significant increase in bilirubin absorbance




Topic area: Neuromuscular system Question no: 3 A 51-year old man referred to a specialist clinic with a complaint of leg weakness. He has had a history of 6-7 years difficulty climbing stairs. On examination he was overweight with proximal weakness of the limbs. Biochemical tests showed a mildly elevated CK. After a thorough investigation, a diagnosis of Pompe disease was made. a) Which enzyme deficiency is

associated with this disease and what is the role of the enzyme [4]

Acid alpha-glucosidase or acid maltase (GAA) [2] GAA catalyses the lysosomal breakdown of glycogen molecules to glucose at position 1-4 or 1-6 [2]

b) What three sample types can be used for measuring these enzymes? [6]

Leukocytes Fibroblasts (allow skin) Muscle

c) State two non-biochemical tests can be used to assists with the diagnosis [4].

Two from - Electromyography - Chest x-ray - Muscle histology

d) What is the main difference between the infantile and adulthood onset forms? [2]

Adulthood form does not involve cardiomyopathy and cardiomegaly.

e) State the inheritance pattern of this disease [2]

Autosomal recessive

f) Which two groups of muscles are most affected in the adult form? [2]

Proximal limb muscles and muscles of respiration




Topic area: Nutrition and gastrointestinal tract Question no: 1 Optimal tissue stores of water soluble vitamins are essential for normal growth and development and for maintenance of health a) List 4 water soluble vitamins of interest

to human health [2] Four from: Vitamins B1, B2, B6, B12, C, folic acid, niacin, biotin

b) List 2 functions of water soluble vitamins [4]

Co-factors for many enzymes (give example) Maintain optimal immune function Act as anti-oxidants

c) State 3 clinical syndromes associated with deficiency of water soluble vitamins and describe how these syndromes can arise [6]

Three from: Beriberi; Korsakoff syndrome (B1 deficincy); stomatitis, glossitis, convulsions, hypochromic anaemia (B2/B6 deficiency); Scurvy (C deficiency); Pellagra (Niacin deficiency) Three from: Inadequate dietary intake; impaired absorption; impaired metabolism; increased requirements; increased losses

d) Giving examples, state 2 biochemical methods for assessing water soluble vitamin status. [4]

Indirect/functional assays – measure enzyme activity E.g. red cell transketolase (B1), red cell glutathione reductase (B2) Direct assays – measurement of vitamin co-factor in blood component E.g. TDP, FAD, PLP , ascorbate by HPLC; B12, folate by immunoassay

e) What are the limitations of the biochemical methods used for assessing vitamin status? [2]

Two from: Indirect methods may be affected by factors other than vitamin status Direct methods – plasma vitamin concentrations don’t reflect intracellular concentrations; limited value in acutely ill patients; may only reflect recent intake

f) State 2 water-soluble vitamins that may be toxic following chronic excessive intake? [2]

Two from Vitamins B6, C, niacin




Topic area: Nutrition and gastrointestinal tract Question no: 2 A 58-year-old male is admitted to Intensive care following gastrointestinal surgery. He is commenced on Total Parenteral Nutrition (TPN) and the following day his biochemistry results are as follows. Na 129 mmol/L K 2.3 mmol/L Urea 11.4 mmol/L Creatinine 156 mmol/L Ca 1.77 mmol/L Albumin 22 g/L Mg 0.4 mmol/L a) What is his adjusted calcium result

detailing the formula you used? [4] Adjusted Calcium (for Albumin) =

(Calcium + (0.02 x (40 - Albumin)) = 2.13 mmol/L

b) What anion might it be useful to measure in this sample and his pre-feeding sample. [2]

Phosphate

c) How is this ‘syndrome’ often described, and an increase in the secretion of which hormone might give rise to these low electrolyte results. [4]

Refeeding syndrome [2] Insulin [2]

d) List two possible clinical symptoms associated with this syndrome. [2]

Two from: Rhabdomyolysis Respiratory Failure Cardiac Failure Hypertension Arrhythmias Seizures Coma Sudden Death

e) Briefly explain the mechanism which is most likely to explain why the Calcium low in this patient [4]

Secondary to Hypomagnesaemia – Mg is required as a co-factor in order to produce PTH

f) List two different methods of measuring Magnesium. [4]

Two from: Atomic Absorption ICP-MS Xylidyl Blue Titan Yellow Ion Selective Electrode Arsenazo III Dry Slide Calmagite




Topic area: Nutrition and gastrointestinal tract Question no: 3 A 22 year old woman underwent a jejunoileal resection and a jejunocolic anastomosis for severe Crohns’ disease. In the months after surgery she complained of evere diarrhoea and was noted to be losing weight despite a good oral intake. A diagnosis f Short Bowel Syndrome is made.

so She is cared for by the Nutrition Team and regains a healthy weight. 2 years after her surgery, however, she is readmitted to hospital with severe loin pain. Investigations attribute this to renal calculi and laboratory analysis show these to be principally composed of calcium oxalate. a) Define Short Bowel Syndrome [2] Insufficient functioning gut for adequate

absorption of nutrition, fluid or electrolytes.

b) State two deficiencies which may occur in patients who have undergone ileal resection [4]

Vitamin B12 Fat soluble vitamins (A, D, E, K)

c) The clinicians wish to exclude D-Lactic acidosis. What is this and why may it occur after this type of surgery? [4]

D-lactic acidosis only occurs in patients with a short bowel and a preserved colon. Colonic bacteria may degrade a surplus of fermentable carbohydrate to form D-lactate which is absorbed but not easily metabolised.

d) Why are requests to clinical laboratories for renal stone analysis becoming less frequent? [2]

Increased clinical use of lithotripsy.

e) Give the main chemical component of 2 other types of renal stone [4]

2 of: Uric acid Calcium phosphate Cystine Magnesium ammonium phosphate Magnesium calcium phosphate

f) Give two reasons why patients who have undergone jejunoileal resection are prone to calcium oxalate renal stone formation? [4]

2 of: • Fat malabsorption, • increased bile salt induced colonic

permeability to oxalate • reduced bacterial degradation of

oxalate, • pyridoxine or thiamine deficiency • hypocitraturia




Topic area: Nutrition and gastrointestinal tract Question no: 4

A 45 year old man with a known history of chronic excess alcohol consumption was admitted to hospital. He was noted to be unkempt and appeared underweight. The admitting doctor prescribed i.v. thiamine supplementation as part of his immediate treatment. 2 days after admission the medical team were contacted by the department of biochemistry to highlight a sudden drop in the patient’s serum phosphate, magnesium and potassium levels to below their reference ranges.

a) Thiamine was prescribed as prophylaxis against which syndrome [2]

Wernicke-Korsakoff syndrome. (Or Wernicke’s encephalitis/ Korsakoff’s Psychosis [1])

b) Describe 2 functions of thiamine in human metabolic pathways [4]

2 of i) co-factor in conversion of pyruvate to acetyl-CoA, ii) co-factor in conversion of 2-oxoglutarate to succinyl-Co A, iii) co-factor in pentose phosphate pathway, iv) metabolism of branched chain amino acids.

c) Why was i.v. thiamine prescribed for this patient. [4]

Potential thiamine deficiency (reduced intake and increased requirements). Lack of thiamine impairs aerobic metabolism of glucose via conversion of pyruvate to acetyl-CoA. Neurons required exclusively on glucose metabolism for energy hence the neurological manifestations of thiamine deficiency.

d) The biochemical changes noted 2 days after admission might be associated with this patient developing what syndrome? [2]

Re-feeding syndrome

e) List 4 other groups of patients who are at increased risk of developing this syndrome [4]

Patients with: i) Anorexia nervosa, Bulimia nervosa, ii) Cancer, iii) Post Operative, iv) Prolonged Fasting

f) Outline the causes of the major metabolic manifestations of this syndrome. [4]

Prolonged starvation results in a change from glucose to ketone metabolism for energy. There is also a decrease in basal metabolic rate and reduced insulin secretion. When carbohydrate is reintroduced there is a high demand for phosphate by metabolic intermediaries and glycolysis, resulting in hypohosphataemia. Increased insulin secretion drives Mg and K into cells reducing their concentrations in plasma.




Topic area: Nutrition and gastrointestinal tract Question no: 5

A 33 year-old female is admitted after a collapse. She has been feeling increasingly tired over the past week. Initial investigations reveal: Hb 7.3 g/dL White cell count 6.4 x 109/L Platelets 210 x 109/L Haematinics have been requested.

a) Describe two findings on haematinics

that might occur if the anaemia is due to iron-deficiency [4]

Two from: Low ferritin Low serum iron Increased TIBC Increased transferring

b) State one feature that might be seen on the blood film of a patient with haemolysis [2]

One from: Reticulocytosis Macrocytosis Spherocytes Red cell fragments

c) List three causes of inherited haemolytic anaemia [6]

Three from: Hereditary spherocytosis Hereditary elliptocytosis G6PD deficiency Pyruvate Kinase deficiency Sickle cell anaemia Thalassemia

d) State two routine laboratory tests that are useful in the initial investigation of macrocytic anaemia [4]

Two from: Folate Vitamin B12 Thyroid function tests

e) If pernicious anaemia is suspected, state one immunological test that might aid diagnosis [2]

One from: Parietal cell antibodies Intrinsic factor antibodies

f) In which part of the gut is vitamin B12 absorbed [2]

Ileum (allow 1 mark for small intestine)




Topic area: Paediatric biochemistry and pregnancy Question no: 1 A 3 week old neonate presents with jaundice, hepatomegaly, dark urine and pale stools. The differential diagnosis includes biliary atresia. a) Jaundice is considered prolonged if

presenting or persisting after how many days? [2]

14

b) Is hyperbilirubinaemia associated with biliary atresia conjugated or unconjugated? [2]

Conjugated

c) Why doesn’t hyperbilirubinaemia in biliary atresia lead to kernicterus [4]

Conjugated bilirubin is unable to cross blood-brain barrier

d) What surgical procedure is used to treat biliary atresia? [2]

Kasai or Kasai-portoenterostomy / hepatoportoenterostomy

e) State 2 investigations that can be used to help differentiate biliary atresia from neonatal hepatitis? [4]

2 from: Ultrasound Radioisotope scan Liver biopsy

f) Explain why an infant with biliary atresia becomes jaundiced? [6]

Obstructed bile flow [2] Bilirubin overflows into blood stream [2] Bilirubin deposited in skin [2]




Topic area: Paediatric biochemistry and pregnancy Question no: 2

A 1month old jaundice neonate has the following blood results, adult reference ranges are shown; Bilirubin 150 umol/L (<20 umol/L) Albumin <2 g/L (32-45 g/L) ALP 432 IU/L (35-104 IU/L) ALT 21 IU/L (10-35 IU/L) GGT Regret, insufficient sample (9-35 IU/L)

a) Is this likely to be a cholestatic or

hepatic liver pathology? (2) Cholestatic (2)

b) Why are insufficient samples more likely to occur in neonates? (2)

Small sample volumes are taken (2)

c) Which fraction of bilirubin is potential life threatening and why? (4)

Unconjugated (2) It can cross the blood brain barrier as it is fat soluble (2)

d) What is the significance of the albumin result in relation to the other tests? (6)

Albumin is undetectable (2) Insufficient sample for GGT suggests small sample volume. (2) Likely miss-sampled albumin test – false result (2)

e) How do you interpret the ALP result? (4)

Raised for an adult. (2) Likely normal for neonate due to bone growth (2)

f) In what way can the laboratory help the interpretation of these results? (2)

Use age related reference ranges (2)





Neonatal screening programmes exist throughout the world to allow early detection of disease.

a) State two diseases which are detected

throughout the UK by neonatal screening. [2]

Two from: Congenital Hypothyroidism Phenylketonuria Cystic Fibrosis

b) State two pre-analytical factors which may invalidate the neonatal blood screen [4]

Two from: Sample taken before day 6 of life Blood transfusion Prematurity Insufficient sample

c) State three criteria which must be considered when evaluating whether a disease should be screened for [6]

Three from: Is the disease adequately defined? What population will be screened? What is the incidence of the condition? Is there a suitable test? What treatment is available? Is screening cost effective? What will be done with equivocal results? Are counselling services available? Has training been provided for healthcare professionals?

d) In some countries, Duchenne Muscluar dystrophy is screened for. a) What test is used to screen [2] b) What is the mode of inheritance of this condition [2]

Creatine Kinase is used to screen X-Linked recessive disease

e) Medium chain Acyl Coenzyme A dehydrogenase deficiency (MCADD) is screened for in parts of the UK. What biochemical test is used to screen? [2]

Acyl Carnitine/Carnitine analysis

f) If a child is diagnosed with MCADD what is the chance that a sibling will also have this condition? [2]

1 in 4 (25%)




Topic area: Paediatric biochemistry and pregnancy Question no: 4 A number of maternal biochemical changes and adaptations occur during healthy and complicated pregnancies. The laboratory may be called upon to support the antenatal care in either circumstance. a) The foeto-placental unit produces

human chorionic gonadotrophin (hCG). What is the approximate expected rate of change in maternal serum hCG in the first trimester of an uncomplicated pregnancy? [2]

Approximately doubles every 2-3 days.

b) State two causes of raised serum or urine hCG, other than the normal progression of an uncomplicated pregnancy. [4]

Two from trophoblastic, germ cell tumours, seminoma, teratoma, choriocarcinoma, hydatidiform mole, bronchial carcinoma, Down’s Syndrome multiple births or incorrectly aged / dated pregnancy.

c) Describe the pattern of change of maternal serum gonadotrophins, oestrogen, progesterone and prolactin during a normal, uncomplicated pregnancy. [6]

Gonadotrophins are suppressed [2] by rising oestrogen and progesterone [2]. Prolactin increases gradually during the first two trimesters, increasing notably in the final trimester [2].

d) Name the chromosomal defect associated with Down’s Syndrome. [2]

Trisomy 21.

e) Name the ultrasound scan abnormality that supports an increased risk of a foetus being born with Down’s Syndrome. [2]

Nuchal (+/- fold) translucency (or thickness)

f) What panel of serum markers are recommended for screening for Down’s syndrome risk for a pregnancy presenting a) between 11 and 14 weeks and b) between 15 and 20 weeks [4]

a) Beta hCG and pregnancy associated plasma protein-A [2]

b) AFP, oestriol and inhibin A between [2] (two markers 1 mark)





Antenatal screening is offered to pregnant women at the appropriate gestational age to allow parents to make informed choices regarding pregnancy outcome. Down’s syndrome is one of the conditions tested for.

a) What chromosomal abnormality is

present in Down’s syndrome? [2] Trisomy 21

b) What three biochemical markers are used for the Triple test (2nd trimester screening)? [3]

Alpha fetoprotein (AFP) hCG Unconjugated oestriol

c) State three pre-analytical factors which may affect the results of the Triple test. [4]

Three from: Weight Multiple pregnancy Ethnic Origin Assisted conception Insulin dependent diabetes mellitus Smoking Bleeding/recent amniocentesis Gestational age

d) Apart from Down’s syndrome what other condition can be detected through antenatal screening? [2]

Neural tube defects (also allow Trisomy 18)

e) What pattern of biochemical results would you expect to find if a fetus had Down’s syndrome? [3]

Low AFP High hCG Low unconjugated oestriol

f) Why do we use multiples of medians to assist the calculation of risk in antenatal screening? [6]

Allows standardisation of values for gestational age. Corrects for normal changes during pregnancy. Allows a comparison of values throughout pregnancy. Allows comparison of results using different assays.





The clinical laboratory has an important role to play in the management of pregnancy. Laboratory tests are used to detect, evaluate and monitor pregnancy

a) The concentration in plasma of many

analytes increases during pregnancy. List 2 analytes whose concentration increases during pregnancy [2]

Two from: Alkaline phosphatase, total T3/ T4, copper, iron, cholesterol, triglycerides, TBG, caeruloplasmin, transferrin, lipoproteins, hCG, progesterone, oestradiol, prolactin

b) How are laboratory tests used in the management of suspected ectopic pregnancy? [6]

Measurement of hCG concentration. Serial hCG samples taken over ~3 days. Expect to see a doubling of hCG concentration every 2 days Static concentration suggests ectopic pregnancy or incomplete miscarriage

c) What analyte is measured in serum as an early indicator of pre-eclampsia? [2]

Urate

d) What does the abbreviation HELLP syndrome stand for? [2]

Haemolysis, elevated liver enzymes, low platelets

e) List three complications associated with poorly controlled maternal diabetes during pregnancy [6]

Three from: Congential malformations e.g. neural tube defects, cardiac abnormalities Obstetric complications e.g. pre-eclampsia, premature labour Neonatal complications e.g. neonatal hypoglycaemia, macrosomia, respiratory distress syndrome Fetal growth retardation

f) What is the most common cause of isoimmunisation disease (Rhesus disease)? [2]

Sensitisation of a RhD negative woman through exposure to D-positive foetal blood in a previous pregnancy




Topic area: Proteins Question no: 1

An 80-year old female presented with back pain and weight loss. She had suffered a recent chest infection and had remained short of breath after recovering from this. Investigations revealed: Hb 8.1 g/dL, ESR 84 mm/h Urea 12.2 mmol/L, Creatinine 304 µmol/L Albumin 24 g/L, Total protein 90 g/L Serum electrophoresis revealed a paraprotein in the λ-globulin region

a) State two further investigations that are

used to confirm the diagnosis of myeloma and the characteristic findings from these investigations [8]

Skeletal survey [2] – lytic lesions [2] Bone marrow aspirate [2]– increased numbers of plasma cells [2]

b) Which immunoglobulin subtype is the most common serum paraprotein present in myeloma? [2]

IgG

c) State one feature that may be evident on the blood film of this patient [2]

One from: Normochromic normocytic anaemia Rouleaux

d) Bence Jones protein may be present in the urine of patients with myeloma. Which immunoglobulin component does this represent? [2]

Light chains

e) State two causes of renal failure in myeloma [4]

Two from: Light chain nephropathy Hypercalcaemia Amyloid Pyelonephritis

f) Why are patients with myeloma susceptible to bacterial infections? [2]

Decreased synthesis of normal immunoglobulins




Topic area: Renal biochemistry and urogenital tract Question no: 1 A Caucasian man aged 55y is waiting on the result of his 24h creatinine clearance before a decision is taken on the administration of the next dose of chemotherapy. The serum creatinine is 120umol/L, the urine creatinine is 6.0mmol/L and the 24h urine volume is 1440 mL. a) What is the formula for calculation of

creatinine clearance. [4] CrCl = Urine [creatinine] x urine flow rate Serum [creatinine]

b) Creatinine clearance is calculated to be 50ml/min. Interpret this creatinine clearance result in the context of a healthy adult population. [2]

CKD 3 (allow mild to moderate renal impairment)

c) Give two advantages and two disadvantages of creatinine clearance measurement in comparison to a single serum creatinine result. [4]

Advantages: Two from: Provides a crude index of glomerular filtration rate; more sensitive index of renal dysfunction; less prone to interference Disadvantages: Two from: Requires accurate timed urine collection; requires blood sample; derived index; relatively expensive; often slower turnaround time

d) What does the abbreviation eGFR stand for? [2]

Estimated glomerular filtration rate

e) The eGFR for the patient was 58 ml/min/1.73m2. How would this result be classified by the UK Chronic Kidney Disease Guidelines? [2]

CKD Stage 3

f) The eGFR result depends to some extent on the method used to measure creatinine. What is the most commonly employed method for measuring creatinine and what is the principle behind this method? [4] What alternative method could be used to improve specificity and the uniformity of creatinine results? [2]

Jaffe method – alkaline picrate yielding orange colour. Kinetic assay used to reduce interference. Specific enzyme method used, usually employing creatininase as first step




Topic area: Renal biochemistry and urogenital tract Question no: 2 Glomerular Filtration Rate (GFR) is normally 120mL/min and is used to assess renal function. The quantity of a substance excreted in the urine in 1 minute is equal to the quantity removed from the plasma by filtration in 1 minute, assuming neither reabsorption nor secretion occurs. There are different ways of measuring or calculating this. a) Name two endogenous markers used to

assess GFR [2] Creatinine; cystatin C

b) List two exogenous markers used to assess GFR [2]

Two from: Cr-EDTA; Tc-DTPA; I-Iothalamate; Iohexol

c) Which exogenous substance is used to assess renal plasma flow, and what property does it have to enable this to occur? [4]

p-aminohippuric acid (PAH) [2]; It is fully removed from the plasma after a single pass through the kidney [2].

d) The 4v-MDRD formula is used to screen for chronic kidney disease (CKD). What does MDRD mean and which variables are used in its calculation? [6]

Modification of Diet in Renal Disease [2]; Creatinine [1], Age [1], Sex [1], Ethnicity [1] (allow Afro-American)

e) What endogenous substance is used as an indication of tubular function, and how is this usually expressed? [4]

Phosphate [2]; Tubular reabsorption of phosphate [2]

f) What is the diagnostic test for type I renal tubular acidosis? [2]

Ammonium chloride loading test (furosemide test one mark)




Topic area: Renal biochemistry and urogenital tract Question no: 3 A 19 year old man presented to his GP with bilateral pitting oedema of his lower limbs and had felt unwell for 4 weeks. Urinalysis showed ++++ protein and the sample was sent to the biochemistry for analysis. a) Define proteinuria in Nephrotic

syndrome. [2] >3g protein in 24 hours

b) Name three complications of the nephrotic syndrome. [6]

Increased susceptibility to infections; thromboembolism; hyperlipidaemia.

c) Pathological proteinurias can be glomerular, tubular or overflow. Define glomerular proteinuria. [2]

Increased transcapillary passage of proteins with molecular weight larger than or equal to albumin.

d) Proteinuria is a risk factor for progressive decline in renal function. Name the two common causes of chronic kidney disease in the UK. [2]

Diabetes mellitus; hypertension

e) Myeloma patients characteristically have Bence-Jones proteinuria. What are Bence-Jones proteins and how do they cause renal damage? [4]

Light chains [2]; There is a direct toxic effect on the tubular cells caused by casts consisting of light chains [2].

f) Albumin excretion is expressed as a ratio to creatinine. What level indicates an increased albumin excretion in males and in females? [4]

>2.5 mg/mmol in males >3.5 mg/mmol in females




Topic area: Renal biochemistry and urogenital tract Question no: 4

Inherited abnormalities of renal tubular function comprise a heterogeneous set of disorders, with manifestations ranging from an asymptomatic biochemical disturbance to end-stage renal failure in childhood

a) Name 2 indicators that may suggest

further investigation for a renal tubular disorder is warranted [2]

Consistent electrolyte disturbance Renal impairment (especially in childhood) Renal stone formation Nephrocalcinosis Positive family history In children – failure to thrive, cognitive impairment, short stature, Rickets

b) Name 2 exogenous causes that may produce a biochemical picture similar to that of a renal tubulopathy [2]

Diuretic use, laxative abuse, chronic liquorice ingestion

c) In a patient presenting with persistent hypokalaemia, state two further investigations that should be carried out to determine the cause [6]

Two from: Bicarbonate measurement, blood pressure measurement, urine chloride and potassium measurement

d) What are the clinical consequences of Fanconi syndrome [4]

Four from: Hypophosphataemia (can lead to Rickets, osteomalacia), glycosuria, hypouricaemia, aminoaciduria, low molecular weight proteinuria, type 2 renal tubular acidosis

e) What are the clinical and biochemical features of Bartter’s syndrome? [4]

At least four from: Renal salt wasting, hypokalaemic metabolic alkalosis, raised renin and angiotensin, polydipsia, polyuria, low-normal BP

f) Name 2 biochemical features that distinguish Bartter’s and Gitelman’s syndromes [2]

Low serum magnesium in Gitelman’s Normal/high urine calcium in Bartter’s, low in Gitelman’s




Topic area: Spectrophotometric methods Question no: 1

Spectrophotometry is an analytical technique that is widely used in the clinical chemistry laboratory. It is applied throughout the core chemistry laboratory and in many of the specialist analytical areas.

a) Define the term “transmittance” and

state its mathematical relationship to absorbance. [2]

Proportion of incident light that passes through a substance. [1] Absorbance is the log of the reciprocal of the transmittance. (A = 2-log10%T ) [1]

b) Give the Beer-Lambert equation and state each term in words. [2]

A = ecl [1] A : absorbance e : molar absorptivity c : analyte concentration l : light path length [1]

c) State two analytical applications of the molar absorptivity. [4]

To from: Calculation of analyte concentration using Beer-Lambert equation. Determination of compound purity. Comparison of relative detection sensitivity of different compounds.

d) What material may be used to calibrate the wavelength accuracy of a spectrophotometer and what property makes it fit for this purpose? [4]

Holmium oxide (glass). [2] Reproducible absorbance spectrum with multiple sharp absorbance peaks at well-defined wavelengths. [2]

e) Describe an analytical problem relating to the specimen that may be encountered with a UV-visible light spectrophotometer. Give one way in which this problem be overcome or minimised? [4]

Either: Interfering compound that absorbs at analytical wavelength. [2] Examine absorbance spectrum or Use kinetic rather than endpoint measurement or Add reagent to modify interfering compound [2] Or: Turbidity. [2] Ultracentrifuge or dilute or Lipoclear [2].

f) Many analytes do not demonstrate a detectable absorbance yet are measured using spectrophotometry. Explain one way that this may be achieved giving one example analyte. [4]

One from: 1) Couple reactions to red/ox of NAD+/NADH or NADP+/NADPH Measure change in absorbance at 340 nm. [2] Most routinely measured enzymes, glucose, ammonia. [2] 2) Formation of coloured complex upon chelation/reaction with chromophore. Direct or coupled reactions. [2] Calcium, cholesterol, lactate.[2] 3) Formation of coloured product upon dye binding. [2] Serum albumin, total protein [2]




Topic area: Therapeutic drug monitoring and toxicology Question no: 1

With regards to anticonvulsant drug therapy

a) Relative to the time of administration of

the drug, when should a sample for phenytoin be collected and why? [2]

Anytime. [1] Phenytoin has a long half-life (>20 hours). [1]

b) List two factors that could increase the concentration of free phenytoin over total phenytoin. [2]

Two from: Reduced protein binding due to: Hypoalbuminaemia, Renal failure, Liver disease. Pregnancy. Displacement of phenytoin from binding proteins by other drugs, e.g. Valproate Drugs that inhibit phenytoin metabolism.

c) Phenytoin can exhibit zero order kinetics above a certain concentration. Describe briefly what zero-order kinetics means [4]

Metabolism is saturable and therefore becomes non-linear [2]. Rate of metabolism becomes independent of concentration [2]..

d) Outline the two pharmacokinetic consequences of zero-order metabolism [4]

Changes in dosing can result in disproportionate changes in drug concentrations [2] and changes in the half-life of the drug [2]

e) Valproic acid is a first line anticonvulsant treatment. Give two reasons why does it not make a good candidate for TDM? [4]

Any two of: Large intra-individual variation. Plasma concentrations do not reflect clinical response. Evidence based target range does not exist. Toxic effects show no clear relationship to plasma concentration.

f) List four criteria for valid therapeutic drug monitoring. [4]

Any four from: • Drug has reversible action at receptor site • Dose has poor correlation with effect • Plasma concentration correlates well with

effect • Narrow therapeutic window • Well-established therapeutic range. • Absence of good clinical markers of effect. • No active metabolites or metabolites

measurable. • Low pharmacodynamic variability.




Topic area: Therapeutic drug monitoring and toxicology Question no: 2 Digoxin is a frequently requested analyte in therapeutic drug monitoring a) In which two clinical conditions is

digoxin used as treatment? [2] Atrial fibrillation and heart failure

b) Changes in which 2 pharmacokinetics parameters alter the half life of digoxin in a patient? How do each of these influence the time taken to reach a steady state? [4]

Clearance (Cl) and apparent volume of distribution (Vd) [2] Increasing Cl will reduce half-life and reduce time to steady state Increasing Vd will increase half-life and extend time to steady state [2]

c) What characteristic of digoxin pharmacokinetics influences the timing of blood sampling when monitoring serum digoxin concentrations? [2]

Large Vd due to tissue binding of digoxin. [2]

d) Name two alterations in serum biochemistry that can influence patients’ sensitivity to digoxin [4]

Two from: Hypokalaemia, hypercalcaemia and hypomagnesemia

e) Name two potential interferences in digoxin immunoassays [4]

Two from: Digoxin-like immunoreactive substances (DLIS) crossreact in assay giving falsely high results. Digoxin metabolites may interfere. Some other drugs (e.g. spironolactone) may interfere

f) In severe digoxin toxicity what influences the decision to treat with digibind (anti digoxin antibody)? What precautions are necessary in the biochemical monitoring of a patient treated with digibind? [4]

Decision taken solely on clinical grounds – restricted to use in life-threatening arrhythmias. [2] (Serum digoxin and K+ are poor indicators of severity of digoxin toxicity) Avoid measuring digoxin in patients treated with Digibind [1]. Risk of rapid development of hypokalaemia so monitor serum K+ closely [1]





An 18 year old female presents to Accident and Emergency reporting an overdose of paracetamol tablets 2 hours previously. Her serum paracetamol concentration on admission is 100mg/L.

a) What advice would you give regarding

interpretation of this paracetamol result? [4]

Sample must be taken at least 4 hours post overdose [2] and is therefore uninterpretable [2].

b) List two categories of patients who should be treated according to the high-risk treatment line on the plasma paracetamol nomogram. [4]

Any two (2 marks each) from: Patients on enzyme-inducing drugs (accept specific examples for 2 marks each: carbamazepine, phenobarbital, phenytoin, primidone, rifampicin, alcohol, St John’s wort) Patients who are malnourished (accept specific examples for 2 marks each: anorexia, alcoholism, HIV-positive)

c) Which intravenous preparation is recommended for treatment of paracetamol overdose if the paracetamol concentration is above the treatment line? [2]

n-acetylcysteine [2] (accept acetylcysteine)

d) Briefly outline the mechanism of action of this antidote. [4]

Supplies sulfhydryl groups [2] (accept augments glutathione reserves) which conjugate a metabolite of paracetamol [2].

e) Which oral antidote may be used in remote areas if the intravenous antidote cannot be given promptly? [2]

Methionine [2]

f) In paracetamol-induced liver necrosis, list two features that indicate a poor prognosis. [4]

Any 2 of (2 marks each): Arterial pH <7.30 or [H+] >50 nmol/L Elevated prothrombin time or elevated international normalised ratio (INR) Elevated plasma creatinine concentration Hepatic encephalopathy





A 43 year-old man is brought to Accident and Emergency by ambulance. He was found collapsed at home. The following blood results are obtained: Na 140 mmol/L K 3.9 mmol/L Cl 111 mmol/L Bicarbonate 6 mmol/L Urea 3.4 mmol/L Creatinine 87 µmol/L Glucose 4.1 mmol/L Osmolality 323 mmol/kg The junior doctor contacts you to discuss the possibility of ethylene glycol analysis.

a) Stating the formula used, calculate the anion gap. [4]

2 marks for formula: ([Na] + [K]) – ([Cl] + [HCO3]) Accept [Na] – ([Cl] + [HCO3]) 2 marks for anion gap: 26.9 (Accept 23).

b) Which method should be used for measurement of serum osmolality in this situation? [2]

Freezing point depression method [2]

c) Stating the formula used, calculate the osmolal gap. [6]

2 marks for formula: Calculated osmolality = 2[Na] + [urea] + [glucose] 2 marks for calculated osmolality: 287.5 mmol/kg 2 marks for: osmolal gap = measured osmolality – calculated osmolality = 35.5 mmol/kg

d) Which further analyte should be measured and its concentration added to the calculated osmolality before deciding if ethylene glycol analysis is appropriate? [2]

Ethanol [2] (accept alcohol)

e) If ethylene glycol is detected, name two antidotes which may be used. [4]

Ethanol [2] Fomepizole [2]

f) Which metabolite of ethylene glycol may cause hypocalcaemia? [2]

Oxalic acid / oxalate [2]




Topic area: Water and electrolytes Question no: 1 A 20-year old male is admitted to hospital with serious head injuries following a motorcycle accident. Over the next few days he produces >3L of urine each day and his serum sodium rises from 130 to 145 mmol/L. a) What is the most likely diagnosis in this

man? [2] Diabetes insipidus

b) What two biochemical tests should be performed to add weight to your diagnosis? [2]

Urine electrolytes and osmolality

c) What dynamic function test could be performed to confirm the diagnosis? [2] Outline the way in which this test is performed and how you would interpret the results? [6]

Water deprivation test [2] Weigh patient before and during test. Supervise to ensure no fluid intake [1] Measure urinary osmolality at hourly (allow) and serum osmolality at 2-hourly (allow 3) intervals [1]. Normal response is rise in urine osmolality to >800mosmol/L (allow 750) [1] If no response after ~8h give DDAVP [1] and continue for 2-3h checking urine osmolality [1] at ~1h intervals – will concentrate to >800 (allow 750) in cranial DI [1]

d) Measurement of the analyte responsible for this condition is rarely of clinical use. Give two reasons for this [4]

Two from: Difficulties with sample collection – unstable Difficulties with assay – lacks analytical sensitivity Long turnaround time from specialist lab Not necessary to reach diagnosis

e) Assuming that your diagnosis is confirmed what treatment would you expect the young man to receive [1] and what biochemical monitoring would you recommend? [1]

DDAVP by nasal spray Monitor and serum and urine osmolality (allow electrolytes as alternative)

f) Apart from trauma give one other cause of this condition. [2]

One from: Pituitary tumour Pituitary infarction. Hypophysectomy Granulomatous disease Nephrogenic (e.g drug induced resistance to ADH with Li or demeclocycline) Allow any other correct cause




Topic area: Water and electrolytes Question no: 2

A 70-year old woman is currently an in-patient on the oncology ward. The registrar calls you for advice on the following results for the patient: Na 115 mmol/L K 3.4 mmol/L Cl 87 mmol/L Urea 1.5 mmol/L Creatinine 32 µmol/L She is currently taking bendroflumethiazide, amlodipine, amitriptyline and aspirin.

a) List 2 pieces of clinical information that

should be sought from the clinician when attempting to deduce the cause of this patient’s hyponatraemia. [4]

Any 2 (2 marks each) from: Clinical impression of hydration status Lying/standing blood pressure History of diarrhoea / vomiting

b) Which 2 drugs listed above may be contributing to the patient’s hyponatraemia? [4]

Bendroflumethiazide [2] Amitriptyline [2]

c) List 2 urine tests which may be helpful in clarifying the cause of this patient’s hyponatraemia. [4]

Osmolality [2] Sodium [2]

d) In general, name two endocrine conditions that should be excluded before a diagnosis of the Syndrome of Inappropriate Antidiuretic Hormone (SIADH) can be formally made in a patient. [4]

Adrenal hypofunction / adrenal insufficiency / Addison’s Disease [2] Hypothyroidism [2] (also accept hypopituitarism)

e) Name one analyte which, if significantly elevated, can cause a pseudohyponatraemia. [2]

Either of: Lipids / Triglycerides [2] Protein (or paraprotein) [2]

f) If treating a symptomatic acute dilutional hyponatraemia, what is the maximum rate at which the serum sodium concentration should be raised? [2]

Accept one of: 0.5-1 mmol/L per hour [2] 8-12 mmol/L in 24 hours [2]


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FRCPath Part 1 Examination in Clinical Biochemistry ......FRCPath Part 1 Examination in Clinical Biochemistry Specimen Short Answer Question Question provided for illustrative and