Laboratory Review Session

Laboratory Review Session

Lucinda Hirahoka

August 2005

Complete Blood Count

• Synonyms: Blood cell profile; blood count; CBC; hemogram

• Test commonly include: WBC, Hct, Hgb, differential count, RBC, WBC and RBC morphology, RBC indices, platelets estimate, platelet count, RDW, and histograms.

• Critical values: Hematocrit <18% or >54%; hemoglobin: <6.0g/dl or 18.0g/dl; WBC on admission: <2500/mm3 or >30,000/mm3; platelets: <20,000/mm3 or >1’000,000/mm3.

• Use: Evaluate anemia, leukemia, reaction to inflammation and infections, peripheral blood cellular characteristics, state of hydration and dehydration, polycythemia, hemolitytic disease of the newborn; manage chemotherapy decisions.

Case Study

• 16 yr old Latino female brought by mother because she is acting tired. ROS neg, except for dietary habits (fast food) and Hx heavy menses. Menses last 7 days, menarche age 10 never had pelvic exam. Junior in high school, gets good grades but school is boring

Case Study

• What lab test would you order to help you with the diagnosis of this patient?

Case Study

• WBC 6.2 Iron 12• RBC 3.38 TIBC 437• Hgb 5.8 Ferritin 0• Htc 20.2 anyso 2+• MCV 60 3+ microcytosis• MCH 17.2 3+ hypochromosis• MCHC 28.8• RDW 17.9

Case Study

• What type of anemia does this patient have?

• What are the other types of anemia?

Red Cell Indices

• The red cell indices provide information about the size, hemoglobin concentration, and hemoglobin weight of an average RBC. The indices include mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC).

Mean Corpuscular HemoglobinConcentration (MCHC)

• MCHC is a measure of the amount of hemoglobin present in the average red blood cell. It defines the concentration of hemoglobin in 100ml of packed red cells. It helps distinguish normally colored (normochromic) red cells from paler (hypochromic) red cells.

Mean Corpuscular Hemoglobin(MCH)

• MCH gives the weight of hemoglobin in an average red cell.

Mean Corpuscular Volume(MCV)

• MCV is a measure of the volume or size of the average red blood cell. The MCV is often used in the evaluation of anemia. The MCV helps to classify the type of anemia and indicates whether they are undersized (microcytic), oversized (macrocytic), or normal (normocytic)

Red Blood Cell Distribution Width

Normally, most red blood cells are equal in size. In many types of anemia there is variability in red blood cell size. RDW is a measure of this variability.

Anisocytosis is a variation in the size of the red blood cell due to unequal hemoglobin content.

• Poikilocytosis is the presence in the blood of erythrocytes showing abnormal variation in shape.

Reticulocyte Count

• Reticulocytes are nonnucleated, immature red cells that remain in the peripheral blood for 24 to 48 hours while they mature. The reticulocyte count reflects the ability of the bone marrow to produce new red blood cells and is adequately responding to the anemia

Serum Iron

• Iron is essential to the formation and function of hemoglobin as well as many other heme and non-heme compounds. Iron appears in the plasma bound to a glycoprotein called transferrin.

• Transferrin is a transporter for iron in the bloodstream

Total Iron Capacity

• Total iron-binding capacity (TIBC) measures the amount of iron that would appear in plasma plus the amount of transferrin available in serum. Normally, transferrin is about 30% saturated.

• In iron deficiency anemia, serum iron levels drop and TIBC increases.

Serum Ferritin

• Ferritin, a major iron-storage protein found in reticuloendothelial cells, normally appears in small quatities in serum. In adults, serum ferritin levels are directly related to the amount of available iron stored in the body.

Case Study

• So what about our case?

White Blood Cells

• White blood cells (leukocytes) include neutrophils, monocytes, lymphocytes, eosinophils, and basophils.

• An increase in any of these cells types can lead to leukocytosis.

Leukocytosis

• Defined as a white blood cell count greater that 11,000 per mm3. It is a normal protective response to stresses such as invading microbes strenuous exercise, anesthesia, and surgery.

• Leukopenia is an abnormal level of white blood cells below 5,000 per mm3, at it may be caused by radiation, shock, and certain chemotherapeutic agents.

Leukocytosis

• The estimated life span of a white blood cell is 11 to 16 days.

• The normal reaction of bone marrow to infection or inflammation leads to an increase in the number of white blood cells, predominantly polymorphonuclear (older neutrophils) leukocytes and less mature cells forms like band cells and metamyelocites which move to the site of injury or infection. The increase of less mature white blood cells is commonly referred to as a “left shift”.

Significance of High and Low WBC

• Neutrophils

• Neutrophilia is the most common type of leukocytosis.

• High: Bacterial Infection, burns, stress, inflammation

• Low: Radiation exposure, drug toxicity, vitamin B12 deficiency, and SLE


• Lymphocytes

• High: Viral infections (mono), some leukemias

• Low: Prolonged illness, immunosuppression, and treatment with cortisol.


• Monocytes

• High: Viral or fungal infections, tuberculosis, some leukemias, other chronic diseases

• Low: Bone marrow suppression, treatment with cortisol


• Eosinophils

• High: Allergic reactions, parasitic infections, autoimmune diseases

• Low: Drug toxicity, stress


• Basophils

• High: Allergic reactions, leukemias, cancers, hypothyroidism, connective tissue disease

• Low: Pregnancy, ovulation, stress, and hyperthyroidism

Sedimentation Rate

• Synonyms: ESR, Westerngren

• ESR is a generally nonspecific measure of inflammation and infection. It is used mainly to follow management of rheumatology patients. Important in clinical evaluation of temporal arteritis and polymyalgia rheumatica.

• KIDNEY FUNCTION

Serum Creatinine• Serum creatinine is a result from catabolism of

creatinine phosphate in skeletal muscle. Normally, the blood creatinine level remains steady because the rate of creatinine excretion in the urine equals its discharge from the muscle. A creatinine level of 1.5mg/dL usually is an indication of poor renal function.

• Concentrations of creatinine only becomes abnormal when about half or more of the nephrons have stopped functioning in chronic progressive renal disease

Serum Creatinine

• Causes of High creatinine includes renal diseases and insufficiency with decreased glomerular filtration (uremia or azotemia if severe); urinary tract obstruction, reduced renal blood flow including CHF, shock and dehydration; rhabdomyolysis causes high serum creatinine.

• Causes of low creatinine include small stature, debilitation, decreased muscle mass, some complex cases of severe hepatic disease. In advanced liver disease low creatinine may result from decreased hepatic production of creatinine and inadequate dietary protein as well as reduced muscle mass.

•

Blood Urea Nitrogen

• Test that measures the blood nitrogen that is part of the urea resulting from catabolism and deamination of amino acids.

• Urea is easily filtered by the renal glomeruli and is partially reasorbed by the renal tubules. Urea nitrogen reflects the ratio between urea production and clearance. Increased BUN may be due to increased production or decrease excretion.

BUN

• High BUN occurs in chronic glomerulonephritis, pyelonephritis, and other causes as in shock. BUN is helpful in following dyalisis patients. Moderate dehydration may increase BUN. Other causes of eleveted BUN are CHF, increased protein catabolism, ketoacidosis, hyperalimentation, it is dependent on renal flow and urinary flow rates. Corticosteroids tend to increase BUN due to increase protein catabolism

• Low BUN occurs in late pregnancy, decrease protein intake and severe liver damage.

• DIABETES

Glycated Hemoglobin

• Synonyms: Fats hemoglobins, GHB, HBA, Hemoglobin A1c

• Glycated hemoglobin is an irreversible glucose-protein bond which extends through the life of an erythrocyte. Glycated hemoglobin values are used to assess long-term glucose control in diabetes.

• Normal range varies from 4% to 7%. There is no age dependence. The risk of microalbuminuria with insulin-dependent DM increases above HBA1c of 10.1%.

Glycated Hemoglobin

• Glycated hemoglobin values are used to assess long-term glucose control in diabetes. Chronic blood loss, hemolytic anemia or other setting for decrease in RBC life span, results in a decrease in the glycated hemoglobin level. Pregnancy as well as chronic renal failure may lower levels of HBA1c

Ketones Bodies

• Synonyms: Ketones, Nitroprusside reaction in blood

• Carbohydrate deprivation and increased catabolism of fatty acids leads to increases in the ketone bodies (acetoacetase and acetone).

Fructosamine

• Synonyms: Glycated Albumin• Normal ranges vary considerably according to method.

Nondiabetics 1.5-2.7 mmol/L, diabetics > OR = 2.0 –5.0 mmol/L depending on the degree of control.

• It is use to evaluate diabetic control, reflecting diabetic control over a shorter time period (2-3 weeks) than that represented by glycated hemoglobin (hemoglobin A1c) (4-8 weeks). Indicated as an index of longer term control than glucose levels, especially in diabetics subjects with abnormal hemoglobin, patients with gestational diabetes, and in type 1 diabetes in children. Fructosamine levels may be useful in screening geriatric populations. Very low albumin levels concentration (<3.0 g/dL) may result in falsely low fructosamine.

• Not a good test for diagnosing or screening for DM.

Ketones

• It helps to diagnosed ketonemia, ketoacidosis resulting from diabetes mellitus, alcoholism, stress, starvation, intestinal disorders including emesis, glycogen storage diseases (von Gierke’s), infantile organic acidemias, and other metabolic disorders.

Ketones

• In infants and children, ketonuria can occur with febrile illnesses, toxic states with marked vomiting or diarrhea.

• In adult healthy men, a fast of 18 hours or greater produces ketonemia at a level that would result in detectable ketonuria. Aging is associated with increased susceptibility to fasting-induced hyperketonemia.

Ketones

• Ketones, Urine• Semiquatitative test to evaluate ketonuria, detect

acidosis, ketoacidosis of alcoholism and diabetes mellitus, fasting, starvation, high protein diets, and isopropanol ingestion. Remains useful as a monitor in known diabetics in type I when ill and during marked hyperglycemia and in type II diabetics during acute illness. In pregnancy, the risk of ketosis is increased; all pregnant type I diabetics are advised to monitor urine for ketosis in first morning urine and when blood glucose is >150 mg/dL.

• LIVER FUNCTION

Liver Profile

Synonyms: Liver battery, liver panel

• Liver profile most often includes total bilirubin, conjugated bilirubin, alkaline phosphatase, LD (LDH), AST (SGOT), with ALT (SGPT), GGT (GGTP). It may also include serum protein electrophoresis, prothrombin time, and hepatitis serology when indicated.

Alanine Aminotrasferase

• Synonyms: ALT; Glutamic Pyruvale Transaminase; GPT; SGPT;Transaminase

• ALT is a cellular enzyme. It is present in the liver, heart, and kidney.

• Reference range: Typical reference range 10-35 units/L. Increases of tenfold occur in some cases of hepatitis and shock.

ALT

• Use: A liver function test, ALT is more sensitive for the detection of hepatocyte injury than for biliary obstruction. ALT is more specific for liver injury than AST (SGOT). Useful for hepatic cirrhosis, and other liver diseases.

Asparate Aminotransferase

• Synonyms: AST; Glutamic Oxaloacetic Transaminase, Serum; GOT; L-Aspartate: 2-Oxoglutarate Aminotransferase; SGOT; Transaminase.

• AST is present in the heart, liver, skeletal muscle, kidney, pancreas. When an increase of AST is from the liver, it is likely to relate to disease of the hepatocyte.

AST

• High AST is caused by various entities like: cirrhosis, alcoholic hepatitis, viral hepatitis, cholecystitis, Reye’s syndrome, mononucleosis, trauma and other striated muscle diseases.

• Very high values, >500 units/L, usually suggest hepatitis or other types of hepatocellular necrosis but can also be found with large necrotic tumors, other types of necrosis or extensive hypoxia, congestive failure, and shock. Unexplained AST elevations should first be investigated with ALT and GGT.

Alkaline Phosphatase (ALP)

• Synonyms: ALP; Phosphatase, Alkaline

• Serum alkaline phosphatase (ALP) activity normally originates from liver and bone. Other sources include intestine and placenta. ALP is excreted in bile. Serum total ALP level provides a useful but nonspecific indication of liver or bone disease. With biliary tract obstruction, the rise in ALP parallels increase in serum bilirubin. An elevated gamma glutamyl transferase would indicate that the liver is the source of the elevated ALP.

• Reference range: Adult normal range is approximately 50-120 units/L.

Alkaline Phosphatase

• Uses: Causes of high alkaline phosphatase include: nonfasting specimen, bone growth, healing fracture, acromegaly, osteogenic sarcoma, liver or bone metastases, leukemia, myelofibrosis, and rarely myeloma. Alkaline phosphatase is used as a tumor marker.

• To confirm biliary abnormality, an additional useful test is GGT which is elevated in hepatobiliary disease.

• Serum ALP is increased during pregnancy. Marked decline of high ALP of pregnancy is seen with placental insufficiency and imminent fetal demise.

Gamma Glutamyl Transferase

• Synonyms: Gamma Glutamyl Transpeptidase; GGT; GGTP; Glutamyl Transpeptidase; GT; GTP.

• Used in diagnosis of obstructive jaundice and alcohol abuse.

• Reference range varies between laboratories.

GGT

• GGT is a biliary enzyme that is especially useful in the diagnosis of obstructive jaundice, intra-hepatic cholestasis, and pancreatitis. GGT is more helpful than AST, SGOT and ALT to work obstruction. In obstructive disease values as high as 5-50 times the upper limit of normal are seen. In infectious hepatitis values seldom go above 5 times normal.

• GGT is the test for cholestasis during or immediately following pregnancy.

• GGT is a biliary excretory enzyme which is more specific for hepatic disease than is alkaline phosphatase. GGT has no origin in bone or placenta.

Total Bilirubin

• Bilirubin: Is a normal, yellow to green pigment of bile derived from the porphyrin structure of hemoglobin.

• Synonyms: Total bilirubin.

• Normal value <1.0 mg/dl

• Increase with biliary obstruction

Bilirubin, Direct

• Bilirubin, Direct• Synonym: Conjugated Bilirubin, Direct bilirubin. It is

formed by unconjugated bilirubin which moves from the plasma to the hepatocyte and joins to glucuronic acid to become conjugated. It becomes a water soluble substance and it can be excreted in the bile.

• Normal values: 0.2-0.4 mg/dl• Elevated direct bilirubin (conjugated fraction) is evidence

of liver or biliary disease.• When conjugated bilirubin is increased in serum, bilirubin

should become positive in the urine.

Indirect Bilirubin

• Indirect Bilirubin or unconjugated is formed by the binding of albumin and bilirubin in the plasma before entering the liver. It is lipid soluble and can cross biological membranes.

• Normal values: <0.8 mg/dl.• Increases with hemolysis (lysis of red blood

cells). Physiologic jaundice of the newborn is caused by unconjugated bilirubin.

Ammonia

• The final product of amino acid and nucleic acid metabolism is ammonia. The liver is the only organ that detoxifies ammonia by converting it into urea.

• It is a useful test to detect hepatic encephalopathy

• THYROID FUNCTION

Thyroid Stimulating Hormone

Synonyms: sTSH; Thyrotropin, Ultrasensitive TSH

• TSH is produced by the anterior pituitary gland, TSH stimulates secretion of T4 (thyrosine) and T3 (triidothryronine). TSH secretion is physiologically regulated by T3 and T4 (feedback inhibition) and is stimulated by TRH (thyrotropin releasing hormone) from the hypothalamus.

• The new sensitive assays (sTSH) permit recognition of hyperthyroidism as well as hypothyroidism, and have become the best single thyroid function test.

TSH

• A diurnal rhythm exists. Peak levels occur at about 11 PM. TSH release is pulsatile.

• Critical values <0.1 mlU/L provides indication or primary hyperthyroidism or exogenous thyrotoxicosis.

• TSH levels are useful to evaluate treatment of hypothyroidism, follow patients that were treated for hyperthyroidism with radiodine or surgery, and for low T4 newborn screen results.

• Among those age 60 and older, low sTSH (<_ 0.1 mlU/L) is a risk factor for atrial fibrillation, which is a risk factor for arterial embolization.

Triidothyronine

• Synonyms: T3; T3 (RIA); T3 total• T3 is a thyroid hormone produced mainly from the

peripheral conversion of T4 ( a prohormone). T3 has a greater biological activity than T4 and binds to TBG less tightly than T4.

• T3 is indicated when sTSH is decreased and FT4 and/or T4 are normal. It helps evaluates the diagnosis of T3 thyrotoxicosis, in which T3 is increased and T4 is within normal limits. T3 toxicosis is occasional found in Graves’ disease, single toxic nodule, multinodular thyrotoxicosis, and following treatment with T3 (Cytomel).

Thyroxine

• Synonyms: T4; T4 by EIA• T4 is the major secretory product of the

thyroid gland. It is carried through the blood bound to thyroxine binding globulin (TBG) (>99.9%), prealbumin, and albumin. T4 secretion is stimulated by thyroid stimulating hormone.

• Normal range 4.0-12.0 ug/dL• Decreased in hypothyroidism.

Free T4

• Thyroxine Free• Synonyms: Free T4• Free T4 is a very small fraction of total thyroxine

(0.04%); it is the metabolically active fraction.• A sensitive test for thyroid function, increased

with hyperthyroidism. Free T4 is indicated when binding globulin (TBG) problems are perceived. Free thyroxine is normal in subjects with high thyroxine binding globulin hormome who are euthyroid (free thyroxine should be normal in nonthyroidal disease.

Thyroid Antimicrosomal and Antithyroglobulin

Synonyms: Antithyroglobuline antibody, antithyroid microsomal antibody, thyroid autoantibodies.

• The most common cause of spontaneous hypothyroidism is chronic autoimmune thyroiditis (Hashimoto’s disease).

• Antibodies to thyroid microsomes (thyroid peroxidase) are present in 70% to 90% of patients with chronic thyroiditis and about 40% of patients with Graves’ disease. Antibodies are also present in smaller percentages of patients with other thyroid diseases and pernicious anemia.

C-Reactive Protein

• Synonyms: CRP• Produced by hepatocytes. C-reactive protein is a

useful but non-specific indicator of acute injury, bacterial infection, or inflammation, sensitive to activation of neutrophils. It is used to try to distinguish bacterial from viral infection, the former causing higher concentrations. It may also be helpful in evaluation of extension or reinfarction after myocardial infarction and in following response to therapy in rheumatic disorders

• HEPATITIS

Hepatitis A• Hepatitis A Antibody, IgM

• Synonyms: Antibody to HAV, IgM; Anti-HAV, IgM; HAVAB• Initially, IgM antibody is usually detectable when clinical symptoms

appear. It disappears 3-6 months afterwards.• Hepatitis A is transmitted by the fecal-oral route, usually foodborne.

Its incubation is 2-7 weeks. Fecal excretion of HAV peaks before symptoms develop. If hepatitis A antibody is IgM, the infection is acute. IgM antibody develops within a week of symptoms onset, peaks in 3 months, and is usually gone after 6 months. Hepatitis A antibody of IgG type is indicative of old infection, is found in almost half of adults, and is not usually clinical relevant. Many cases of hepatitis A are subclinical, particularly in children. Presence of IgG antibody to HAV does not exclude acute hepatitis B or C.

Hepatitis B Serology

• Hepatitis B Serology• Test commonly includes: Antigen and Antibody

test currently available for hepatitis B include hepatitis B surface antigen (HBeAg), hepatitis B surface antibody (anti-HBe), hepatitis B core antibody-total (anti-HBc-Ab-total), hepatitis B core-IgM (anti-HBc-IgM), hepatitis B early antigen (HBeAg), and hepatitis B early antibody (anti-HBe).

Hepatitis B

• For evaluation and differential diagnosis of acute hepatitis, serologic testing is recommended for HBsAg, HBsAb, HBcAb (IgM), and HAV (IgM). HBsAb is the first marker to appear, detecting the HBV surface protein or envelope. Persistence of the HBsAg for periods in excess of 6 months indicates a chronic carrier state or chronic hepatitis.

• Hepatitis B virus (HBV) is spread parenterally, homosexual or heterosexual activity, and by exposure to saliva or other potentially infectious secretions.

Hepatitis B• The test available for hepatitis B have the

following significance:• HBsAg: A positive test indicates that the patient

has HBV viremia and is infectious; it does not distinguish acute from chronic infection.

• Anti-HBs: A positive test indicates that the patient has protective immunity to HBV, either due to immunization or previous HBV infection.

• Anti-HBc-total: A positive test indicates that the patient has been exposed to HBV; by itself, this test does not distinguish active from resolved infection, or acute from chronic infection

Hepatitis B

• Anti-HBc-IgM: A positive indicates acute infection

• HBeAg: A positive test indicates that this patient is highly infectious; this is not a marker for acute infection as chronic carriers can be persistently positive, and it is not recommended for routine testing

• Anti-HBe: A positive test indicates that the patient is likely to produce HBeAb sometime soon and resolve their infection; not recommended routine testing.

Hepatitis C

• Synonyms: HCV Serology• Most cases of post-transfusion non-A, non-B viral hepatitis are

caused by HCV. Hepatitis C is characterized by a prolonged natural history.

• In the United States, Hepatitis C accounts for probably more than 90% of viral hepatitis that used to be categorized as non-A, non-B hepatitis. HCV is transmitted primarily by parenteral means and tends to produce chronic liver diseases, including asymptomatic, chronic active hepatitis and cirrhosis. HCV infection is also associated with the development of hepatocellular carcinoma. The disease progression appears to be extremely slow; 15 years for chronic active hepatitis, 20 years for cirrhosis, and 25 years to reach hepatocellular carcinoma.

Electrolytes

• Electrolytes, Serum or Plasma• Test commonly includes: Sodium, potassium,

chloride, often total CO2.• It is use to evaluate electrolyte and acid-base

balance, screen water balance, diagnose respiratory and metabolic acid-base balance, evaluate hydrational status, diarrhea, dehydration, ketoacidosis in diabetes mellitus and other disorders, evaluate alcoholism and other toxicity states.

Potassium

• Potassium Serum or Plasma

• K+ is the major intracellular cation, K+ is very commonly measured as one of the serum or plasma electrolyte and as a urinary electrolyte as well.

• Reference range: Plasma 3.5-5.0 mmol/L. Hemolysis of the sample may cause increase levels of K+.

Hypokalemia

• Low potassium occurs with vomiting, diarrhea, fistulas, laxatives, diuretics, burns, excessive perspiration, some cases of alcoholism and folic acid deficiency, in acid base abnormalities, renal tubular disorders. Cushing’s syndrome or aldosteronism caused marked hypersecretion of adrenal steroid hormones causing loss of potassium.

Hyperkalemia

• Hyperkalemia: reflects generally inadequate renal excretion, mobilization of potassium from the tissues, or excessive intake or administration. It also occurs with hemolysis, trauma, with administration of K+, ACE inhibitors, Addison’s disease(because of the absence of aldosterone, which result on potassium buildupand sodium depletion), acidosis including ketoacidosis, insulin, potassium sparing diuretics, non-steroidal anti-inflammatory drugs.

Sodium

• Sodium, Blood

• Sodium (Na+) with its accompanying anions is the most important extracellular osmotically active solute. Plasma or serum sodium is representative of the extracellular compartment (insterstitial fluid and plasma). Na+ is the major cation of extracellular fluid.

Hypernatremia

• Hypernatremia occurs from loss of water or from sodium retention. It is found in dehydration and with diuretic use. Dehydration is an expression bearing an implication of water depletion. When both water and sodium are lost, the expression “volume depletion” is appropriate. Increased insensible lost with hyperpnea, sweating, high ambient temperature, fever, or burns causes hypernatremia. Nasogastric protein feeding with insufficient fluids may cause hypernatremia, as can vomiting or diarrhea.

Hypernatremia

• Hypernatremia with obvious cause may relate to Cushing’s syndrome, central or nephrogenic diabetes insipidus with insufficient fluids, primary aldosteronism, and other diseases. Severe hypernatremia may be associated with volume contraction, lactic acidosis, and azotemia. Increased hematocrit may provide evidence of dehydration. Apparent mild hyponatremia with very high glucose may actually mean hypernatremia. Infusion of hypertonic saline or sodium bicarbonate or ingestion of sodium may cause sodium retention.

Hyponatremia

• Hyponatremia occurs with nephrotic syndrome, cachexia, hypoproteinemia, iv glucose infusion, CHF, mineralocorticoid deficiency, and cystic fibrosis. Serum sodium is a predictor of cardiovascular mortality in patients with severe CHF. Mineralocorticoid deficiency leads to hyponatremia, hypovolemia, and hypokalemia through inadequate sodium and water resorption and diminished potassium excretion. Hyponatremia without CHF or dehydration may occur with hypothyroidism, the syndrome of inappropriate secretion of antidiurectic hormone (SIADH), renal failure, or renal sodium loss.

• Sodium decreasing to levels <115 mmol/L can lead to significant neurological dysfunction with cerebral edema and increased intracraneal pressure.

• URINE

Urine Dipstick Testing

• Color: Normal color is clear and light yellow• Protein: Only test for albumin. It is not very sensitive

since protein excretion must exceed 300-500 mg/day for the dipstick to be positive. The upper limit of normal protein excretion is 150mg/day. This is important for patients with DM because an earlier finding of diabetic nephropathy is the excretion of 150-300mg of protein per day (microalbuminuria).

• PH: Provides information on the degree of urine acidification. In patients with UTI and pH >7.5 is suggestive of the presence of a urea-splitting organism.


• Urine osmolality: Is a measure of so;ute concentration in the urine.

• Specific Gravity: Defined as weight of a volume of urine compared to equal volume of distilled water. Generally corresponds with the urine osmolality

• Glucose: In normal renal function glucosuria is not seen until plasma glucose exceeds 180mg/dL


• Blood: Presence of blood or heme• Leukocyte Esterase: A positive result indicates

pyuria.• Nitrite: A positive result indicates precense of

bacteria in the urine that can convert nitrates to nitrite.

• Bilirubin: A positive test shows presence of conjugated hyperbilirubinemia

• Ketones: In a diabetic a positive test might indicate the possibility of ketoacidosis.

HEART DISEASE

Cardiac Enzymes

• Troponin I

• Is the most specific cardiac marker of choice to diagnose myocardial infarction. It is very specific to myocardial injury.

• Troponin I rises 4 to 6 hours after onset and peaks after 24-48 hours and will remain elevated for up to two weeks after the event.

Homocysteine

• Elevated levels of homocysteine have been associated with an increased risk of arterial and venous thrombosis. Studies have shown that an elevated homocysteine level is a strong, independent risk factor for atherosclerosis in the coronary, aortic, carotid, and peripheral vasculature.

Cardiac Enzymes

• MB Fraction of Creatine Kinase (CK-MB)

• Is more specific to cardiac injury when compared to creatine kinase.

• CK-MB rises 4-6 hours after onset of MI

• Myoglobin: is an oxygen binding protein released from myocardial cells after injury. It can be detected 1-4 hours after the insult.

Congestive Heart Failure

• B-type natriuretic peptide (BNP) is a cardiac neurohormone specifically secreted from the cardiac ventricles in response to ventricular volume expansion, pressure overload, and resultant increased wall tension.

Documents

Laboratory Review Session