Title: Dynamic Function Test Handbook

Title: Dynamic Function Test Handbook

Authors Names: Jonathan Clayton

Scope: Clinical Chemistry laboratory service users Classification: Information

Replaces:

To be read in conjunction with the following documents: Clinical Chemistry Laboratory Handbook

Unique Identifier: BIO-I-P-011

Review Date: June 2021

This document is no longer authorised for use after this date

Issue Status: Approved Issue No: 4 Issue Date: May 2019

Authorised by: Joanna Borzomato Authorisation Date: May 2019

Document for Public Display: Yes

After this document is withdrawn from use it must be kept in an archive for 10 years.

Archive: server Date added to Archive:

Officer responsible for archive:

Clinical Biochemistry

Dynamic Function Test Information for Users of the

PAWS Biochemistry Service

Q-Pulse Ref: BIO-I-P-011 Q -Pulse Revision No: 4 Authorised By: Joanna Borzomato Page 2 of 37

Page 2 of 37

Contents Dynamic Function Tests ......................................................................................................................................3

24 Hour Urine Collection ................................................................................................................................4

Investigation of Anaphylaxis ...........................................................................................................................5

Calcium Excretion Index (Calcium Clearance Ratio) .......................................................................................6

Creatinine Clearance ......................................................................................................................................7

Cushing’s Syndrome .......................................................................................................................................8

24 hour Urinary Free Cortisol (24h UFC) ....................................................................................................9

Overnight Dexamethasone Suppression Test (ONDST) ........................................................................... 10

Low Dose Dexamethasone Suppression Test (LDDST) ............................................................................ 11

High Dose Dexamethasone Suppression Test (HDDST) ........................................................................... 13

Glucose Tolerance Test................................................................................................................................ 15

Mixed Meal Test for Investigation of Reactive Hypoglycaemia .................................................................. 18

Glycosade Loading Test ............................................................................................................................... 20

Growth Hormone Suppression Test (GTT with Growth Hormone) ............................................................. 22

Glucagon Stimulation Test ........................................................................................................................... 24

Arginine Stimulation Test ............................................................................................................................ 26

Clonidine Stimulation Test........................................................................................................................... 27

Gut Hormone Profile ................................................................................................................................... 28

48/72 hour Prolonged Supervised Fast (Insulinoma) .................................................................................. 29

Luteinising Hormone Releasing Hormone (LHRH) or Gonadotrophin Releasing Hormone (GnRH)

Stimulation Test ........................................................................................................................................... 31

Short Synacthen Test (Addison’s Disease Screen) ....................................................................................... 33

Short Synacthen Test (Congenital Adrenal Hyperplasia) ............................................................................. 34

Thyrotropin Releasing Hormone (TRH) Stimulation Test ............................................................................ 35

Water Deprivation Test ............................................................................................................................... 36





Page 3 of 37

Dynamic Function Tests This handbook deals with a selected number of the most frequently requested dynamic tests. For details of

other tests not detailed in this handbook, please contact the Duty Biochemist on (0161 20) 68212 for

advice.

These tests, properly performed, provide more information than can be obtained from single

determinations. Incorrectly performed dynamic test results inconvenience the patient, mislead the clinician

and waste precious laboratory resources. Dynamic function tests are usually performed at the request of an

Endocrine consultant. When requesting a dynamic function test, interfering medications or medications

used for the treatment of the symptoms of the disease being investigated (e.g. antihypertensives when

investigating Cushing’s or phaeochromocytoma) should be ceased wherever possible. For further

information or for clarification please discuss the test with an Endocrine consultant or the Duty Biochemist

(0161 206 8212), or see the Pathology at Wigan and Salford (PAWS) Department of Clinical Biochemistry

User Guide available on the Intranet.

Since many tests involve accurate collection of 24 hour urine specimens this section explains the

procedures.

Other tests are arranged in alphabetical order.





Page 4 of 37

24 Hour Urine Collection Accurately timed, complete urine collections are a vital part of many tests, particularly those concerned

with renal function. Careful attention to detail, especially by the ward, is necessary.

Obtain a urine container with the correct preservative (see PAWS Biochemistry User Handbook). Choose a

convenient time to start the collection usually in the early morning, e.g. 8am. If collecting on a ward, it is

convenient to have a routine time for starting all collections. If results are required on the day of

completion, specimens must be received in the laboratory by 10am.

Day 1 8am Ask the patient to empty their bladder completely and discard this

specimen.

Thereafter collect all urine passed into this container for the next 24 hours.

Day 2 8am Ask the patient to empty their bladder completely and add this specimen to

the collection.

Collect no more urine.

Ensure the sample is fully labeled:

PATIENT’S FULL NAME (*mandatory requirement*)

DATE OF BIRTH

HOSPITAL NUMBER or NHS NUMBER (if available)

START TIME AND DATE OF COLLECTION

FINISH TIME AND DATE OF COLLECTION

Notes

1. Ensure that urine and faeces are passed separately.

2. If the container is full before completion of collection, use a second one with the same

preservative, and send both to the laboratory.

3. If any specimen of urine is not collected or accidentally discarded during the collection, discontinue

the test and start again





Page 5 of 37

Investigation of Anaphylaxis Indication

In the investigation of suspected Anaphylactic reactions.

Preparation of Patient

None

Sample requirements

Collect two 5mL EDTA blood samples (red top Sarstedt Monovette), one for full blood count and one for

mast cell tryptase, at the following times:

Initial sample as soon as feasible after resuscitation.

Second sample 1-2h (no later than 4 hours) after onset of symptoms

Third sample either at 24hrs or at convalescence (e.g. in follow up allergy clinic). This is a measure

of baseline tryptase levels as some individuals have higher baseline levels.

Transport to laboratory and analysis

Ensure that the samples are clearly labelled with patient details and time and date.

Transport to the laboratory immediately after collection. Samples for mast cell tryptase are analysed in

Salford Immunology.

Documentation

This should accompany the request and should include: time and date of reaction; surgical procedure,

drugs administered, clinical manifestations, previous medical/anaesthetic history (if known), any risk

factors (e.g. penicillin allergy) and management of reaction and outcome.

Interpretation

Transiently raised tryptase is seen within 30-180 minutes of systemic acute anaphylaxis. It is chronically

raised in Mastocytosis. A baseline sample (24 hr post event) is therefore essential for interpretation.

References

NICE CG 134 Anaphylaxis: assessment to confirm an anaphylactic episode and the decision to refer after

emergency treatment for a suspected anaphylactic episode. 2011

Management of a patient with suspected anaphylaxis during anaesthesia, The Association of Anaesthetists

of Great Britain and Ireland 2009

Suspected Anaphylactic Reactions Associated with Anaesthesia, Association of Anaesthetists of Great

Britain and Ireland 2008

Assay information: Adverse (Anaphylactoid) reactions to Intravenous drugs, Supra-regional Assay Service,

Sheffield.

http://www.nice.org.uk/nicemedia/live/13626/57537/57537.pdf

http://www.aagbi.org/sites/default/files/ana+AF8-laminate+AF8-2009.pdf

http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2044.2008.05733.x/pdf

http://www.sas-centre.org/assays/protein-reference-units/adverse-anaphylactoid-reactions-to-intravenous-drugs





Page 6 of 37

Calcium Excretion Index (Calcium Clearance Ratio) Clinical Use

Investigation of suspected familial hypocalciuric hypercalcaemia (FHH) in patients with hypercalcemia.


The patient is fasted overnight for 10-16 hours (water is allowed). The patient should not be taking any

diuretics during the test, and should be vitamin D replete.

Procedure

1 Collect a random sample of urine passed between 9-11 am (in white top plain container).

2 Collect a blood sample (8ml brown top gel-tube) during the same time

3 Send the urine and blood samples together to the Laboratory clearly writing Calcium Excretion Index on

the request form (Biochemistry section).

Interpretation

Calcium Excretion Index Result Interpretation

≤0.013 Familial Hypocalciuric Hypercalcaemia (FHH)

0.013 – 0.037 Equivocal – other investigations and referral to

endocrinology

≥0.037 Primary Hyperparathyroidism

Calcium excretion index is calculated as:

𝐶𝐸𝐼 =𝑈𝐶𝑎 × 𝑆𝐶𝑟

𝑈𝐶𝑟 × 1000

Where:

UCa = urine calcium concentration in mmol/L

SCr = serum creatinine concentration in µmol/L

UCr = urine creatinine concentration in mmol/L

Reference

Foley KF, Urine Calcium: Laboratory Measurement and Clinical Utility, Lab Medicine 2010; 41(11):683-686

https://doi.org/10.1309/LM9SO94ZNBHEDNTM





Page 7 of 37

Creatinine Clearance Requires a 24 hour plain urine (see guidance on 24 Hour Urine Collection) and a paired serum for urea and

electrolytes (U&E) taken as soon after completion of the collection as possible. The urine and serum

samples should be delivered to the lab together.

Creatinine clearance is calculated as:

𝐶𝑟𝐶𝑙 =1000 × 𝑈𝑉𝑜𝑙 × 𝑈𝐶𝑟𝑒𝑎𝑡𝑖𝑛𝑖𝑛𝑒

𝑈𝐷𝑢𝑟𝑎𝑡𝑖𝑜𝑛 × 60 × 𝑆𝐶𝑟𝑒𝑎𝑡𝑖𝑛𝑖𝑛𝑒

Where:

CrCl = creatinine clearance in mL/min

UVol = urine volume in mL

UCreatinine = urine creatinine concentration in mmol/L

UDuration = duration of urine collection in hours

SCreatinine = serum creatinine concentration in µmol/L





Page 8 of 37

Cushing’s Syndrome Note: Oestrogens [oral contraceptive pill (OCP) and hormone replacement therapy (HRT)] are known to

increase cortisol binding globulin (CBG) and thus may over-estimate serum cortisol levels. It is

recommended that OCP/HRT is stopped 6 weeks prior to testing.

Investigations

It is strongly recommended that if Cushing’s Syndrome is suspected, a Clinical Endocrinologist is contacted

prior to commencing investigations.

Guidelines for the investigation of Cushing’s Syndrome have been published by the Endocrine Society in

2008. The following algorithm and protocols for first-line testing shown below are taken from or based on

these guidelines.

Measurement of cortisol in saliva can be arranged however a collection pack and instructions are required.

Please discuss this test with an Endocrine consultant and arrange with the Duty Biochemist (0161 20

68212).

https://doi.org/10.1210/jc.2008-0125





Page 9 of 37

24 hour Urinary Free Cortisol (24h UFC)


The test can be performed fasting or fed.

Contraindications

Ensure patient is not taking steroids in any form (including creams and nasal sprays). Interpretation may be

difficult if performed at a time of intercurrent illness, when cortisol secretion would physiologically increase

anyway.

Procedure

See guidance on 24 Hour Urine Collection

Interpretation

UFC should be less than 180 nmol/24 hr. If greater levels are confirmed on 2 occasions then the patient

should undergo further investigation. The sensitivity and specificity of this test are fairly low and hence 3

UFCs are required to exclude Cushing’s syndrome. If all 3 UFCs are normal then it is extremely unlikely that

the patient has Cushings syndrome. Conversely, if the cortisol level on one sample is four times the upper

limit of normal then Cushing’s syndrome is highly probable. False positive results seen in patients with

pseudocushings, alcoholism and PCOS.

When 3 UFC are performed: 3.3% false positive rate, 5.6% false negative rate.

Notes

Urinary free cortisol is measured using LC-MS/MS.





Page 10 of 37

Overnight Dexamethasone Suppression Test (ONDST)


The test can be performed on an in or out-patient basis and fasting is not required.

Contraindications

Pregnancy

Epilepsy

Suspected cyclic Cushing’s Syndrome

In the above cases, 24-UFC is recommended as the first line test.

Procedure

1 Dexamethasone (1 mg) is given orally at 11pm.

2 A single blood specimen (serum gel tube – brown top Sarstedt Monovette) is collected for serum

cortisol between 8am – 9am the following morning.

Interpretation

Normal individuals suppress serum cortisol to <50 nmol/L.

Patients who fail to suppress should be tested with the low dose dexamethasone test and referred to

endocrinology.

Notes

a) Patients on enzyme inducing drugs (e.g. anticonvulsants and rifampicin) may rapidly metabolise

dexamethasone and give false positive results (i.e. no suppression). Women on oestrogen therapy may

not adequately suppress due to increased cortisol binding globulin.

b) Normal subjects rarely (2%) fail to suppress with overnight dexamethasone. False positives may occur

with: depression (due to the development of a reversible glucocorticoid resistance), severe systemic

illness and patients with renal failure on dialysis. Patients with simple obesity do not have an increased

rate of false positive results.

c) In patients with glucocorticoid resistance syndrome basal ACTH and cortisol levels are elevated and

only partially suppressible with dexamethasone. The patients do not look cushingoid, although women

are hirsute because of high adrenal androgens secondary to elevated ACTH levels.

d) Alcohol must be rigorously avoided for a minimum of 3 days prior to this test (alcohol-induced pseudo-

Cushing’s syndrome)





Page 11 of 37

Low Dose Dexamethasone Suppression Test (LDDST)

Indication

Second line test for Cushing's syndrome.

Preparation of patient

This is usually an inpatient test with no patient preparation required. Occasionally the test can be done as

an outpatient (if you are confident that the patient is likely to take their tablets on time). Patients require a

9am serum cortisol and plasma ACTH prior to the first dose of dexamethasone. The patient must be able to

take the dexamethasone exactly 6 hourly for the next 48 hours. A repeat 9am serum cortisol and plasma

ACTH is required 6 hours after the final dose of dexamethasone.

Stop all oral oestrogen therapy (OCP or HRT) 6 weeks prior to test. Patients on sex steroid implants might

generate results that are difficult to interpret.

Contraindications

Patients on enzyme inducing drugs e.g. anti-convulsants may rapidly metabolise dexamethasone.

Oestrogens (e.g. pregnancy, HRT or COC) may induce cortisol binding protein and artificially

increase total cortisol levels.

Care in diabetes mellitus and patients who are psychologically unstable.

Procedure

Day Time ACTH (Li-Hep plasma)

Cortisol (serum sample)

Dexamethasone 0.5 mg orally

1 9am

3pm

9pm

2 3am

9am

3pm

9pm

3 3am

9am

NOTE: Samples for ACTH MUST be received by the laboratory within 15 minutes of venepuncture.





Page 12 of 37

Interpretation

If the day 3 9am cortisol value is < 50nmol/L the patient has shown suppression. Failure to suppress is seen

in the autonomous secretion of cortisol found in Cushing's syndrome. However, since there are several

common conditions associated with impaired cortisol suppression following a LDDST (e.g. morbid obesity,

depression), the result should always be interpreted in conjunction with the degree of clinical

suspicion/signs or symptoms of patient.

Sensitivity and Specificity

Suppression in patients with Cushing's syndrome is rare (2-5%). In some reported cases metabolism of

dexamethasone occurs slowly and so higher circulating levels of serum cortisol than expected are found.

This test is more specific than the overnight suppression test with a lower false positive rate. Failure of

suppression in patients may be seen in patients with systemic illness, endogenous depression, or on

enzyme inducing drugs e.g. phenytoin or rifampicin.

References

Newell-Price J et al., The Diagnosis and Differential Diagnosis of Cushing’s Syndrome and Pseudo-Cushing’s

States. Endocrine Reviews 1998; 19(5):647-672

https://doi.org/10.1210/edrv.19.5.0346





Page 13 of 37

High Dose Dexamethasone Suppression Test (HDDST)

Indication

Third line test for distinguishing between pituitary and ectopic secretion of ACTH. ACTH-producing

adenomas of the pituitary retain some responsiveness to the suppressive effects of dexamethasone, unlike

ectopic ACTH secreting tumours, which do not.


This is usually an inpatient test with no patient preparation required. Occasionally the test can be done as

an outpatient (if you are confident that the patient is likely to take their tablets on time). Patients require a

9am serum cortisol and plasma ACTH prior to the first dose of dexamethasone. The patient must be able to

take the dexamethasone exactly 6 hourly for the next 48 hours. A repeat 9am serum cortisol and plasma

ACTH is required 6 hours after the final dose of dexamethasone.

Stop all oral oestrogen therapy (OCP or HRT) 6 weeks prior to test. Patients on sex steroid implants might

generate results that are difficult to interpret.

Contraindications

Patients on enzyme inducing drugs e.g. anti-convulsants may rapidly metabolise dexamethasone.

Oestrogens (e.g. pregnancy, HRT or COC) may induce cortisol binding protein and artificially

increase total cortisol levels.

Care in diabetes mellitus and patients who are psychologically unstable.

Procedure

Day Time ACTH (Li-Hep plasma)

Cortisol (serum sample)

Dexamethasone 2.0 mg orally

1 9am

3pm

9pm

2 3am

9am

3pm

9pm

3 3am

9am

NOTE: Samples for ACTH MUST be received by the laboratory within 15 minutes of venepuncture.





Page 14 of 37

Interpretation

Suppression of cortisol levels by greater than 50% occurs in 75% of patients with Cushing’s disease, 10-15% of patients with ectopic ACTH secretion and 0-6% of patients with adrenal tumours. The day 3 9am cortisol after the 48hr test is considered to be the most sensitive means of differentiating between Cushing’s disease and ectopic production.

References

Newell-Price J et al., The Diagnosis and Differential Diagnosis of Cushing’s Syndrome and Pseudo-Cushing’s

States. Endocrine Reviews 1998; 19(5):647-672

https://doi.org/10.1210/edrv.19.5.0346





Page 15 of 37

Glucose Tolerance Test The diagnosis of Diabetes Mellitus should be made according to the World Health Organisation Guidelines

2006 and the World Health Organisation Guidelines on the Use of HbA1c in the Diagnosis of Diabetes

Mellitus 2011.

Glucose tolerance tests (GTT) are rarely needed to diagnose diabetes mellitus. If the patient has suggestive

symptoms, measure the fasting blood glucose. A fasting plasma glucose of 7.0 mmol/L or above on two

different days is consistent with diabetes mellitus even in the absence of symptoms under the 2006 W.H.O.

criteria. These criteria also defined a new category of intolerance called Impaired Fasting Glycaemia (IFG),

where fasting plasma glucose is between 6.1 and 6.9 mmol/L. The Guidelines state that people with IFG

should have a full GTT to determine tolerance status.

Glycated haemoglobin (HbA1c) can sometimes be used to identify those who have diabetes or are at high

risk of developing diabetes. However in conditions where glucose values can change quickly (such as

pregnancy) or there are Hb or RBC abnormalities (haemoglobinopathies, haemolysis) the HbA1c value

might not accurately reflect glycaemic exposure and a GTT should be performed instead.


The patient should continue with their normal diet (i.e. a normal intake of carbohydrate) for at least three

days prior to the test.

The patient must not have anything to eat or drink (other than plain water) after 10pm on the evening prior

to the test or on the day of the test, until it is completed. During the test, the patient should be at rest and

should NOT smoke.

Owing to diurnal variation of glucose tolerance, tests should be commenced between 9am and 10am.

Contraindications

This test should NOT be performed in patients who fulfil the criteria for diabetes mellitus. These are:

1) a fasting plasma glucose >7.0 mmol/L on two or more occasions, or

2) clinical symptoms of diabetes, e.g. polydipsia, polyuria, ketonuria and rapid weight loss with a

random plasma glucose >11.1 mmol/L.

This test should not be performed in patients who are under physical stress, e.g. post-surgery, trauma or

infection; or extreme psychological stress, as the catecholamine response will induce temporary

carbohydrate intolerance and may give misleading results.

http://whqlibdoc.who.int/publications/2006/9241594934+AF8-eng.pdf


http://www.who.int/diabetes/publications/report-hba1c+AF8-2011.pdf






Page 16 of 37

Procedure

1 Check the patient’s fasting blood glucose using a point of care testing glucose meter.

If the result is ≥9 mmol/L, the test should be abandoned.

2 Take a 2ml blood specimen for plasma glucose (fluoride oxalate plasma - yellow top Sarstedt

Monovette). Fluoride oxalate tubes should be filled to the line and the blood mixed immediately with

the anticoagulant by gentle inversion of the tube. Label the tube clearly with the patient's full name,

date of birth and hospital number (if available), and the time and date of sampling, as for all subsequent

specimens.

3 Administer a 75g anhydrous glucose load in 200-300mL of water.

[N.B. The glucose preparations used may differ across SRFT and WWL (e.g. Glucosol (SRFT Pharmacy),

PolyCal, MaxiJul or Lucozade). Prepare the glucose preparation according to manufacturer’s instructions,

ensuring that the final volume is a maximum of 300mL and contains 75g anhydrous glucose].

The patient should consume the glucose load in its entirety within 5 minutes.

4 Take a further blood specimen for plasma glucose (fluoride oxalate plasma - yellow top Sarstedt

Monovette) exactly 2 hours after ingestion of the glucose load (ensure sample fully labelled and time of

sampling stated). Send the 2 blood specimens with an appropriately completed request form to the

laboratory.

5 The test is now complete and the patient should be given something to eat and drink before being sent

home.

Interpretation

MALES AND NON-PREGNANT FEMALES:

Normal Impaired

Fasting

Glycaemia

Impaired

Glucose

Tolerance

Diabetes Mellitus Diabetes

Mellitus

Fasting <6.1 6.1-6.9 <7.0 ≥7.0 ≥7.0

And And And Or And

2 hour <7.8 <7.8 7.8-11.0 ≥11.1 ≥11.1

Note: if at least one other abnormal

plasma glucose level on another

occasion, or HbA1c >48 mmol/mol,

then a diagnosis of DM can be made.

Adapted from WHO Guidelines 2006 and 2011.







Page 17 of 37

PREGNANT FEMALES:

Normal Impaired Glucose Tolerance of Pregnancy

Gestational

Diabetes

Mellitus

Fasting <5.1 ≥5.1

And And/Or

2 hour <7.8 >7.8 & <8.5 ≥8.5

Adapted from International Association of Diabetes and Pregnancy Study Groups (IADPSG)/ADA Guidelines

2013.

Notes

1 If the patient vomits, the test should be abandoned.

Send the fasting blood glucose sample to the laboratory with an explanatory note on the request form.

2 Pregnant patients diagnosed with gestational diabetes mellitus should be reassessed with a GTT 3

months post-partum.

3 Some drugs can affect GTT results, particularly glucocorticoids. Please state on the request form if the

patient is receiving any steroids.

References

World Health Organisation (2006) Definition and diagnosis of diabetes mellitus and intermediate

hyperglycaemia: report of a WHO/IDF consultation

World Health Organisation (2011) Use of glycated haemoglobin (HbA1c) in the diagnosis of diabetes

mellitus

NICE PH38 (2012) Preventing type 2 diabetes: risk identification and interventions for individuals at high

risk

American Diabetes Association (2013) Diagnosis and Classification of Diabetes Mellitus. Diabetes Care 2013;

36(S1):S67-S74

http://care.diabetesjournals.org/content/36/Supplement+AF8-1/S67.full.pdf+htk-






http://publications.nice.org.uk/preventing-type-2-diabetes-risk-identification-and-interventions-for-individuals-at-high-risk-ph38







Page 18 of 37

Mixed Meal Test for Investigation of Reactive Hypoglycaemia Clinical Use

The Investigation of Reactive Hypoglycaemia.

The patient with a history suggestive of postprandial hypoglycaemia should undergo a mixed meal test.

That meal should include the components recognized by the patient as likely to cause hypoglycaemia and

should be conducted over 5 hours.

An oral glucose tolerance test should NEVER be used for the evaluation of suspected postprandial

hypoglycemia.


This test should be performed as an inpatient test.

The patient should fast overnight. All non-essential medications should be withheld until the test is

completed.

Procedure

For a mixed meal diagnostic test, the patient consumes a meal that usually leads to symptoms and is then

observed for up to five hours.

1 Collect basal blood samples for glucose (fluoride oxalate tube – yellow top Sarstedt Monovette); serum

cortisol (serum gel tube – brown top Sarstedt Monovette), and insulin, proinsulin and C-peptide (serum

gel tube – brown top Sarstedt Monovette [SEPARATE SAMPLE]). Send all to lab immediately (to arrive at

laboratory within 60 minutes of collection).

2 Give the patient their mixed meal. The patient should consume the meal within 10-15 minutes.

3 Collect blood samples for glucose, and insulin, proinsulin & C-peptide at 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 h

after giving the meal. The blood samples should reach the laboratory within 15 minutes of collection

4 Collect blood samples for glucose, cortisol, insulin, proinsulin and C-peptide at 5 h.

5 The patient should be closely observed throughout the test and any hypoglycaemic symptoms and their

time noted on the request form. (Instruct the patient to report if they feel unwell or symptomatic

during the test).

6 If it is judged necessary to treat before 5 hours because of severe symptoms, obtain samples for

glucose, (fluoride oxalate tube – yellow top Sarstedt Monovette); insulin, proinsulin, and C-peptide

(serum gel tube – brown top Sarstedt Monovette [SEPARATE SAMPLE]); cortisol and sulphonylureas

(serum gel tube – brown top Sarstedt Monovette) before administering carbohydrates.

Interpretation

A fall in venous plasma glucose to 2.5 mmol/L or less between 2-5 h post mixed meal together with

hypoglycaemic symptoms and a rise in serum cortisol of at least 220 nmol/L are consistent with, but no

proof of reactive hypoglycaemia. The rise in serum cortisol is considered essential for clinical significance to

be attached to the other findings.





Page 19 of 37

Notes

1 No urine samples are required.

2 Smoking is not allowed throughout the test and only plain water is allowed.

3 Samples for insulin, proinsulin, C-peptide and sulphonylureas will NOT be referred for testing if the

patient does not exhibit hypoglycaemia during the test.

Reference

Gama R et al., Clinical and laboratory investigation of adult spontaneous hypoglycaemia. J Clin Pathol 2003;

56:641-646.

Cryer PE et al., Evaluation and Management of Adult Hypoglycemic Disorders: An Endocrine Society Clinical

Practice Guideline. J Clin Endocrinol Metab 2009; 94:709-728

http://jcp.bmj.com/content/56/9/641.full.pdf+htk-


https://doi.org/10.1210/jc.2008-1410





Page 20 of 37

Glycosade Loading Test Clinical Use

To determine fasting tolerance in patients with Glycogen Storage Disease (GSD)


DO NOT FAST prior to hospital attendance

Admit patient to CPIU at 10.00am.

Procedure

1 Continue overnight feed until baseline bloods have been taken.

Measure POCT glucose on arrival.

2 Insert IV cannula. Once secure, insert a second IV cannula on other arm and administer 100 mL 0.9%

saline at 5 mL/hr to keep line patent. This second cannula is to be used should the first cannula fail.

Allow patient to rest for 20 minutes.

3 After 20 minutes rest, take baseline blood samples as detailed below.

DISCARD 1 FULL BROWN TOP TUBE BEFORE EACH HOURLY SAMPLING.

4 Weigh 100g Glycosade and mix with 200 mL water.

Give this orally, or via gastrostomy tube.

RECORD TIME OF ADMINISTRATION

If given via gastrostomy tube, flush with 50 mL water after administration.

5 Discontinue overnight feed.

Water can be consumed freely. No food / milk / sugar to be consumed for the duration of the test.

6 A jug of water, one sachet of S.O.S.25 and the blue beaker should be by the patient at all times.

7 Monitor POCT glucose and take bloods hourly as detailed below.

The test should take 8 hours, or less if the patient becomes hypoglycaemic. If the test is terminated early

please inform the duty biochemist (68212) or on-call BMS (bleep 3102) if after 5pm.

Baseline 1hr 2hr 3hr 4hr 5hr 6hr 7hr 8hr/completion of test

Fluoride Oxalate (Yellow)

Glucose Lactate

Lithium Heparin (Orange)

Free Fatty Acids (FFA) B-Hydroxy Butyrate (B-OHB)

Serum (Brown)

Creatine Kinase (CK) Urate

8 At the end of the fast, give 1 sachet S.O.S.25 orally or via gastrostomy





Page 21 of 37

9 Carbohydrate containing meal should be taken within 30 minutes otherwise severe hypoglycaemia may

develop.

10 If POCT glucose <3 mmol/L or if symptoms of hypoglycaemia develop, the fast should be discontinued, 1

sachet S.O.S.25 should be given either orally or via the gastrostomy tube. Bloods as per “Completion of

Test” should be taken.

11 If the S.O.S.25 is not tolerated, commence 10% Glucose IV at 200 mL/hr

Consult Metabolic Consultant regarding discharge of patient.

For full protocol, please contact Metabolic Medicine consultants.





Page 22 of 37

Growth Hormone Suppression Test (GTT with Growth Hormone) The American Association of Clinical Endocrinologists have produced updated Guidelines regarding the

Diagnosis of Acromegaly which advocate the use of GTT for Growth Hormone Suppression as the Gold

Standard.

Indication

The investigation of gigantism or acromegaly


The patient should be fasted for 10-16 hours and throughout the period of the test, but may drink plain

water. The patient should be at rest throughout the period of the test and smoking is not allowed.

Procedure

1 Check the patient’s fasting blood glucose using a point of care testing glucose meter.

If the result is ≥10 mmol/L, the test should be abandoned.

Take blood specimens and give glucose as detailed below. Yellow top (Fluoride oxalate) tubes should

be filled to the line and the blood mixed immediately with the anticoagulant by gentle inversion of the

tube. Label the tubes clearly with the patient's full name, date of birth and hospital number, and the

time and date of sampling, as for all subsequent specimens.

Time Glucose (fluoride oxalate plasma - yellow top Sarstedt Monovette)

Growth Hormone (Serum Gel tube – brown top Sarstedt Monovette)

0 Min (also request IGF-1 on this sample)

0 Min

Give the appropriate glucose load prepared as follows:

Glucose

Water

Adults: 75 g 200 mL

Children over 12: 1.25 g/kg

(up to a maximum of 75g)

200 mL

Children aged 3-12: 1.75 g/kg

(up to a maximum of 75g)

200 mL

The patient should drink this within a 5 minute period. Give the patient a further 100 mL of water to drink following the glucose. Drink within 5 minutes.

30 Min

60 Min

90 Min

120 Min

180 Min

https://www.aace.com/files/acromegaly-guidelines.pdf

https://www.aace.com/files/acromegaly-guidelines.pdf





Page 23 of 37

2 The test is now complete and the patient should be given something to eat and drink before being sent

home.

Interpretation of Results

Normal individuals respond by suppression of at least one GH level to <0.4 µg/L. In Acromegaly or

Gigantism serum GH concentration remains >0.4 µg/L and there is frequently a paradoxical rise in response

to hyperglycaemia.

Notes

a This test is not indicated as a diagnostic procedure in patients with a blood glucose >10 mmol/L after an

overnight fast.

The ingestion of 75 g glucose by a fasting diabetic patient may be dangerous.

b Patients occasionally vomit after ingestion of the glucose and the test is abandoned. This is not

necessarily a justification for abandoning the test, and continuation is often the simplest expedient,

provided an explanatory note is made on the request form accompanying the samples.

The interpretation of results may be sufficiently clear to avoid the repetition of the test on a future

occasion.

c In addition to abnormal GH levels, carbohydrate intolerance is found in about 25% of acromegalic

patients.

Reference

Arafat AM et al., Growth Hormone Response during Oral Glucose Tolerance Test: The Impact of Assay

Method on the Estimation of Reference Values in Patients with Acromegaly and in Healthy Controls, and

the Role of Gender, Age, and Body Mass Index. J Clin Endocrinol Metab 2008; 93(4):1254-1262

https://doi.org/10.1210/jc.2007-2084





Page 24 of 37

Glucagon Stimulation Test Indication Assessment of growth hormone and ACTH reserve. Contraindications Malnourished patients who have not eaten for >48h. Precautions Patients may feel nauseous during and after the test (administration of intravenous anti-emetics can be considered). Late hypoglycaemia may occur (patients should be advised to eat small and frequent meals after the completion of the test). Preparation of Patient The patient is fasted from midnight. Procedure

1 At 8.30am cannulate the patient, and then allow the patient to rest on the bed for 30 minutes.

2 At 9.00 start the test. Monitor pulse and BP every 30 minutes.

3 Take samples and give glucagon as follows:

Time Glucose (yellow top Sarstedt Monovette)

Growth Hormone and Cortisol (Serum Gel tube – brown top Sarstedt Monovette)

0 Min

0 Min Give Glucagon 1 mg sub-cutaneously (1.5mg if patient >90kg) OR Glucagon 15µg/kg

30 Min

60 Min

90 Min

120 Min

150 Min

180 Min

210 Min

240 Min

4

Send all the samples together to the Laboratory for Cortisol and Growth Hormone estimations.





Page 25 of 37

Interpretation Normal response: Growth Hormone >7 µg/L (males) or >10 µg/L (females) after 2 – 3 hours. Peak cortisol should be >500 nmol/L. In adults with growth hormone deficiency, peak growth hormone levels fail to rise above 3 µg/L. Notes Priming with sex steroids is recommended in prepubertal children who are over 10 years of age (either chronological or bone age). Prescribe Stilboestrol 1mg 12 hourly for 48 hours prior to test. This test must be performed at least 4 hours after any food and drink. Reference Molitch ME et al., Evaluation and Treatment of Adult Growth Hormone Deficiency: An Endocrine Society Clinical Practice Guideline J Clin Endocrinol Metab 2011; 96:1587-1609 Yuen KCJ, Glucagon Stimulation Testing in Assessing for Adult Growth Hormone Deficiency: Current Status and Future Perspectives. ICRN Endocrinology 2011, doi:10.5402/2011/608056 Barth JH, Pituitary Tests for Young Children, Leeds Pathology Biochemical Investigations in Laboratory Medicine accessed 03.01.2019.

https://doi.org/10.1210/jc.2011-0179

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3262627/pdf/ENDOCRINOLOGY2011-608056.pdf

http://www.pathology.leedsth.nhs.uk/dnn+AF8-bilm/Investigationprotocols/Pituitaryprotocols/PituitaryFunctionTestsforShortChildren.aspx

http://www.pathology.leedsth.nhs.uk/dnn+AF8-bilm/Investigationprotocols/Pituitaryprotocols/PituitaryFunctionTestsforShortChildren.aspx





Page 26 of 37

Arginine Stimulation Test Indication

Assessment of Growth Hormone reserve.

Note the Glucagon Stimulation Test is the preferred method for testing Growth Hormone reserve in adults.


Fast the patient overnight.

Procedure

1 At 8.00am cannulate the patient in both arms, and then allow the patient to rest on the bed for 60 minutes.

2 At 9.00am start the test. Monitor pulse and BP every 15 minutes.

3 Take samples and give Arginine as follows:

Time Growth Hormone (Serum Gel tube – brown top Sarstedt Monovette)

0 Min

0 Min Give 30g Arginine in 100 mL 0.9% saline as infusion over 30 minutes.

30 Min

60 Min

90 Min

120 Min

4

Send all the samples together to the Laboratory for Growth Hormone estimations.

5 Keep the patient lying down for an hour after the test, and check the patient's pulse and blood

pressure half-hourly and also before allowing them to get up.

Interpretation

If the plasma GH concentration peaks at ≥7 µg/L, further investigations are not indicated.

If the plasma GH concentration peaks at ≤3 µg/L, then a second alternative test of Growth Hormone

reserve may be necessary.

Reference

Alba-Roth J et al., Arginine Stimulates Growth Hormone Secretion by Suppressing Endogenous

Somatostatin Secretion. J Clin Endocrinol Metab 1988; 67:1186-1189

US National Library of Medicine Growth Hormone Stimulation Test accessed 03.01.2019.

https://doi.org/10.1210/jcem-67-6-1186

http://www.nlm.nih.gov/medlineplus/ency/article/003377.htm





Page 27 of 37

Clonidine Stimulation Test Indication

Assessment of Growth Hormone reserve.

Note the Glucagon Stimulation Test is the preferred method for testing Growth Hormone reserve in adults.


Fast the patient overnight (4 hours for infants). Measure their height and weight and determine the surface

area from appropriate tables.

Procedure

1 At 8.30am cannulate the patient, then allow the patient to rest on the bed for 30 minutes.

2 At 9am start the test. Monitor pulse and BP every 15 minutes.

3 Take samples and give Clonidine as follows:

Time Glucose (yellow top Sarstedt Monovette)

Growth Hormone and Cortisol (Serum Gel tube – brown top Sarstedt Monovette)

0 Min

0 Min ADULTS >18y: Give Clonidine 25 - 50 microgram i/v CHILDREN <18y: Give Clonidine 0.15 mg/m2 body surface area i/v

30 Min

60 Min

90 Min

120 Min

150 Min

4

Send all the samples together to the Laboratory for Cortisol and Growth Hormone estimations.

5 Keep the patient lying down for an hour after the test, and check the patient's pulse and blood

pressure half-hourly and also before allowing them to get up.

Interpretation

If the plasma GH concentration peaks at ≥7 µg/L, further investigations are not indicated.

If the plasma GH concentration peaks at ≤3 µg/L, then a second alternative test of Growth Hormone

reserve may be necessary.

References

Gil'Ad et al., Oral Clonidine as a Growth Hormone Stimulation Test, Lancet 1979; 314:278-280

Lanes R and Hurtado E, Oral clonidine — an effective growth hormone-releasing agent in prepubertal

subjects, Journal of Pediatrics 1982; 100:710-714

http://www.sciencedirect.com/science/article/pii/S0140673679902939

http://www.sciencedirect.com/science/article/pii/S0022347682805696





Page 28 of 37

Gut Hormone Profile Clinical Use

Diagnosis of neuroendocrine tumours of the gastrointestinal tract.


The patient should be fasted overnight. Proton pump inhibitors will lead to an elevation of some hormones

and should be stopped 2 weeks prior to the test (H2 blockers stopped at least 3 days prior to the test).

Procedure

1 Collect 3 x EDTA tube (red top Sarstedt Monovette).

2 Mix by gentle inversion.

3 Send the sample to the laboratory IMMEDIATELY. Please inform laboratory reception that these

samples are unstable and need immediate processing.

[Note: samples MUST be separated and frozen at -20°C within 15 minutes of venepuncture].

Interpretation of Results

The gut hormone profile consists of the following hormones (with attached normal adult ranges)

Vasointestinal Polypeptide (VIP) <30 pmol/L

Pancreatic Polypeptide (PP) <300 pmol/L

Gastrin <40 pmol/L

Glucagon <50 pmol/L

Somatostatin <150 pmol/L

Chromagranin A <60 pmol/L

Chromagranin B <150 pmol/L

Reference

Supraregional Assay Service Handbook, www.sas-centre.org 2011.

http://www.sas-centre.org/





Page 29 of 37

48/72 hour Prolonged Supervised Fast (Insulinoma) Indication

To demonstrate fasting hypoglycaemia if there is a suspicion of an insulinoma despite a normal overnight

plasma glucose level.


1 Admit patient to perform fast under close supervision with glucose (oral or i/v) available.

2 Admit ONLY to an endocrine ward (Langtree) (WWL) or MIU (SRFT).

3 Advise admit ONLY on a Monday or Tuesday before noon

4 Patients may drink plain water.

Procedure

1 Cannulate patient and continue/commence 48 hr fast.

2 Water is allowed. Patient should be active during waking hours but should not leave the ward.

3 Capillary blood glucose measurements should be done at regular (4 hr) intervals and whenever the

patient has symptoms suggestive of hypoglycaemia. Decrease to 1 hr intervals if the patient has glucose

<3.5 mmol/L.

4 Ketones should be suppressed with insulinoma even though patient is fasting because of the excess

insulin. Therefore urinary ketone testing (urine dipstick screen performed on ward) can give some

additional information.

Actions

When capillary blood glucose is <3.0 mmol/L or symptoms are convincing:

1 Bleep doctor urgently.

2 Take venous blood for urgent glucose (fluoride oxalate – yellow top Sarstedt Monovette), insulin and C-

peptide (serum sample – brown top Sarstedt Monovette). Send to biochemistry lab without delay to be

separated and frozen within 60 mins. Ring biochemistry up for an urgent glucose.

3 Take blood for sulphonylurea screen in a serum tube (serum gel tube – brown top Sarstedt Monovette).

4 Do not reverse hypoglycaemia until the lab confirms hypoglycaemia or unless the patient becomes

unconscious or fits.

5 Hypoglycaemia achieved if <2.2 mmol/L age under 60 or <2.5 mmol/L if over 60 years old. If achieved,

make sure the bloods have gone for insulin and C-Peptide and allow the patient to eat. They should not

go home until after a good carbohydrate meal.

6 If NOT hypoglycaemic then continue the fast.

7 If no symptoms have occurred at end of 48 hrs then take final samples for glucose, insulin and C-

peptide and sulphonylurea screen. In selected patients, the fast can be extended to 72 hours. [Samples

will only be despatched for analysis if hypoglycaemia is demonstrated]





Page 30 of 37

Reference

Gama R et al., Clinical and laboratory investigation of adult spontaneous hypoglycaemia. J Clin Pathol 2003;

56:641-646







Page 31 of 37

Luteinising Hormone Releasing Hormone (LHRH) or Gonadotrophin Releasing

Hormone (GnRH) Stimulation Test Indication

Investigation of impaired hypothalamic or anterior pituitary function.

Please note these tests are NOT recommended by the RCOG or the RCP.

Preparation of Patient and Procedure

The patient does not require fasting. The test should preferably be carried out in the morning (8am –

10am).

1 Obtain a zero minute blood sample (5 mL) into a serum gel tube (brown top Sarstedt

Monovette).

2 Give 100 microgram of LH RH, i/v as a bolus.

3 Obtain further specimens for FSH and LH at 20 and 60 minutes.

Interpretation

In adult males the LH concentration rises 7- to 8-fold and FSH 2-fold above the basal levels. The peak

concentrations usually occur at 20 minutes. If the 60 minute value is greater than the 20 minute value, the

response is said to be delayed. The response in women is qualitatively similar but varies in magnitude with

the stage of the menstrual cycle and is dependent on circulating steroid concentrations particularly E2. The

LH response is 3- to 4-fold greater in the luteal phase than in the follicular phase with the greatest response

in the pre-ovulatory phase. The FSH responses are similar but less marked.

In children:

The LHRH test is often difficult to interpret and results should be interpreted alongside clinical findings

including full pubertal staging, testicular volume (boys) or ovarian ultrasound (girls). Puberty is a continuum

and so is the response to the GnRH test.

Normal response: Increment of 3-4 IU/L of LH and 2-3 IU/L of FSH

Pubertal LH level (>5 IU/L) and/or LH:FSH >1 are suggestive of gonadotrophin-dependent precocious

puberty

Suppressed LH/FSH with high testosterone and oestradiol indicate gonadotrophin-independent

precocious puberty

Increase in FSH level, without a rise in LH indicates the child is prepubertal

Predominant FSH response in premature thelarche

In premature adrenarche, values are prepubertal

Notes

a) It should be established that both gonadal steroid and basal FSH/LH levels are low before embarking

upon this test.

b) Response can be variable.

c) If required, this test can be performed at the same time as the TRH test.





Page 32 of 37

References

Practical Clinical Biochemistry. Ed. Gowenlock AH 6 Edition 1988 Redwood Burn

Menon PSN and Vijayakumar M, Precocious Puberty—Perspectives on Diagnosis and Management, The

Indian Journal of Pediatrics 2014; 81(1):76–83

https://doi.org/10.1007/s12098-013-1177-6

https://doi.org/10.1007/s12098-013-1177-6





Page 33 of 37

Short Synacthen Test (Addison’s Disease Screen) Indication

For the Investigation of Adrenal Insufficiency. There is no evidence to support the use of this test in the

management of steroid replacement or withdrawal.


The patient is not required to fast but the test should be performed in the morning with the patient

recumbent. There is a slight risk of allergic reaction. The test should not be done within two weeks of

pituitary surgery.

Prednisolone, methylprednisolone and prednisone may all interfere in the Cortisol assay therefore the

patient should not take their steroid dose on the morning of the test.

Oestrogens [oral contraceptive pill (OCP) and hormone replacement therapy (HRT)] are known to increase

cortisol binding globulin (CBG) and thus may over-estimate cortisol levels. It is advised that OCP/HRT are

stopped 6 weeks prior to testing wherever possible.

Procedure

1 Take a basal sample of blood for serum cortisol (serum gel tube – brown top Sarstedt Monovette).

2 Inject i/m or i/v 250 microgram of tetracosactide (Synacthen).

3 Take a further blood sample for serum cortisol at 30 mins.

4 Send all the blood samples together, carefully labelled with the time of each sample, with the request

form to Biochemistry.

Caution

Do not delay starting therapy if adrenal failure is clinically suspected. If steroids are to be given as an

emergency treatment take a blood sample for serum cortisol (serum gel tube – brown top Sarstedt

Monovette) and ACTH (lithium heparin – orange top Sarstedt Monovette) IMMEDIATELY BEFORE

administration so that the diagnosis can be confirmed retrospectively. Once the short Synacthen test has

been performed it is unnecessary to withhold treatment in patients suspected of adrenocortical

insufficiency.

Interpretation

The interpretation of Short Synacthen Tests is method specific. At PAWS we currently utilise the Siemens

Cortisol method on the Siemens Advia Centaur XP. By this method, the test should be interpreted as

follows:

Basal cortisol 30 minute cortisol

Normal response ≥200 nmol/L ≥500 nmol/L

Equivocal response 350-500 nmol/L

Inadequate response ≤350 nmol/L

Reference

El-Farhan N et al., Clinical Endocrinology 2013; 78:673-680

http://onlinelibrary.wiley.com/doi/10.1111/cen.12039/full





Page 34 of 37

Short Synacthen Test (Congenital Adrenal Hyperplasia) Indication

For the diagnosis of congenital adrenal hyperplasia (CAH). It is often used in hyperandrogenised women to

diagnose late-onset CAH.


The patient is not required to fast but the test should be performed in the morning with the patient

recumbent. There is a slight risk of allergic reaction. The test should not be done within two weeks of

pituitary surgery.

Prednisolone, methylprednisolone and prednisone may all interfere in the Cortisol assay and, if possible,

the patient should not take their steroid dose on the morning of the test.

Oestrogens [oral contraceptive pill (OCP) and hormone replacement therapy (HRT)] are known to increase

cortisol binding globulin (CBG) and thus may over-estimate cortisol levels.

Procedure

1 Take a basal sample of blood for serum 17-hydroxyprogesterone (17-OHP) and serum cortisol (serum

gel tube – brown top Sarstedt Monovette).

2 Inject i/m or i/v 250 microgram of tetracosactide (Synacthen).

3 Take a further blood sample for serum 17-OHP and serum cortisol at 30 mins.

4 Send all the blood samples together, carefully labelled with the time of each sample, with the request

form to Biochemistry.

Interpretation

The interpretation of cortisol results in Short Synacthen Tests is method specific. See Short Synacthen Test

(Addison’s Disease Screen).

CAH is suggested by a baseline 17-OHP ≥10 nmol/L. A baseline of >100 nmol/L is diagnostic of homozygous

21-hydroxylase deficiency.

The ratio Δ17𝑂𝐻𝑃

Δ𝐶𝑜𝑟𝑡> 0.028 gives 70% diagnostic accuracy for heterozygote 21-hydroxylase deficiency, where

∆17𝑂𝐻𝑃 = 17𝑂𝐻𝑃30 − 17𝑂𝐻𝑃𝑏𝑎𝑠𝑎𝑙and ∆𝐶𝑜𝑟𝑡 = 𝐶𝑜𝑟𝑡𝑖𝑠𝑜𝑙30 − 𝐶𝑜𝑟𝑡𝑖𝑠𝑜𝑙𝑏𝑎𝑠𝑎𝑙.

Adults with rarer forms of CAH (e.g. 11-β-hydroxylase deficiency) have flat 17-OHP responses to synacthen.

Reference

El-Farhan N et al., Clinical Endocrinology 2013; 78:673-680

Kreutzmann DJ et al., Aust. Paediatr. J.1989; 25:340-345

Barth J et al., Biochemical Investigations in Laboratory Medicine, 2001 ACB Venture Publications

http://onlinelibrary.wiley.com/doi/10.1111/cen.12039/full

http://onlinelibrary.wiley.com/doi/10.1111/j.1440-1754.1989.tb02353.x/abstract





Page 35 of 37

Thyrotropin Releasing Hormone (TRH) Stimulation Test Indication

Investigation of anterior pituitary function. The development of TSH assays capable of accurate

measurements below 0.1 mU/L has obviated the need for the TRH test in most cases of thyroid practice

except perhaps in the differential diagnosis of TSHoma and thyroid hormone resistance (high TSH and high

thyroxine).


The patient does not require fasting. The test should preferably be carried out in the morning (8am –

10am).

Procedure

1 Obtain a zero minute blood sample (5 mL) into a serum gel tube (brown top Sarstedt

Monovette).

2 Give 200 microgram of TRH i/v as a bolus. For children, 7 microgram/kg up to 200 microgram

maximum.

3 Obtain further specimens for TSH at 20 and 60 minutes.

Interpretation

In normal subjects TSH levels rise to between 5-25 mU/L at 20 minutes with an increment over the basal

value of at least 3 mU/L, thereafter decreasing slightly at 60 minutes.

In secondary hypothyroidism due to pituitary disease, basal TSH levels are low or low-normal and the TSH

response is impaired.

Notes

1 The use of this test is limited to the investigation of suspected secondary hypothyroidism.

2 Stress, psychological disturbances and drug therapy (including glucocorticoids) may impair the TSH

response and results must be interpreted accordingly

3 If required, this test can be performed at the same time as the LH RH test.

References

Barth J et al., Biochemical Investigations in Laboratory Medicine, 2001 ACB Venture Publications





Page 36 of 37

Water Deprivation Test Indication

To differentiate primary polydipsia, cranial diabetes insipidus (DI) and nephrogenic DI.

Preparation

Inform laboratory that test is being undertaken. Exclude adrenocortical or thyroid deficiency. Stop DDAVP

8h beforehand in patients already on treatment, but continue with anterior pituitary hormone

replacement. Fluid and food are allowed until 8am on the morning of the test.

Procedure

8am insert i/v cannula, weigh patient, patient empties bladder, measure urine volume and send for

osmolality. No fluids allowed throughout test. Measure BP, pulse, weight, urine and serum osmolality, and

urine volume hourly for 8 hrs (use table on page 38).

Proceed to DDAVP test if urine osmolality rises <30 mOsm/kg (in toto) over 3 successive urine samples.

STOP TEST if urinary osmolality ever >750 mOsmol/kg, serum osmolality >300 mOsmol/kg (give DDAVP 2

microgram i/v and fluids), weight loss >5% of baseline value (check serum osmolality), urine output exceeds

5 litres in absence of weight loss (suggests surreptitious drinking).

Interpretation

Post-dehydration osmolality (mOsm/kg)

Post DDAVP osmolality (mOsm/kg)

Diagnosis

plasma urine urine

283-293 > 750 > 750 normal

> 293 < 300 < 300 nephrogenic diabetes insipidus

> 293 < 300 > 750 cranial diabetes insipidus

< 293 300-750 < 750 chronic polydipsia

< 293 300-750 < 750 partial nephrogenic DI or primary polydipsia

> 293 300-750 > 750 partial cranial DI

Submaximal urine concentration (500 – 700 mOsmol/kg) with no response to DDAVP (desmopressin)

suggests psychogenic polydipsia or partial nephrogenic DI.

Reference

SRFT Endocrinology Investigation Manual.

Thompson CJ. Polyuric states in man. Clin Endocrinol Metab 1989; 3:473-497

Miller M et al., Recognition of partial defects in antidiuretic hormone secretion. Ann Intern Med 1970;

73:721-729

http://intranet.srht.nhs.uk/policies-resources/trust-policy-documents/trust-wide-clinical/gen/end106/?locale+AD0-en

http://ac.els-cdn.com/S0950351X89800126/1-s2.0-S0950351X89800126-main.pdf?+AF8-tid+AD0-59900bea-be59-11e3-a75f-00000aab0f6c+ACY-acdnat+AD0-1396877851+AF8-0bcbd7a2907a0c8ddc78e9db3788ddff

http://annals.org/article.aspx?articleid+AD0-684913

http://annals.org/article.aspx?articleid+AD0-684913





Page 37 of 37

WATER DEPRIVATION TEST

NAME:_______________________________

Hospital No.:__________________ Location:_________________

Date of Birth:__________________ Requesting Clinician:__________________

Weight BP U&Es Serum Osmolality

Urine Osmolality

Urine Volume

08:00

08:30

09:30

10:30

11:30

12:30

13:30

14:30

15:30

16:30

If urine osmolality remains <750 mOsmol/kg, give DDAVP 2 microgram i/m. Give free fluids from now onwards.

17:30

18:30

19:30

20:30

Documents

Title: Dynamic Function Test Handbook