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CLINICAL CHEMISTRY

 

Test Name

     Sample

Test Interference

Remarks

 

  • Fasting blood sugar

 8 hour fast, water intake is accepted

Serum.

 Avoid hemolysis, assay immediately

Caffiene,corticosteroids,oral contraceptives,phenytoin, diuretics, ascorbic acid, antihistamines, indomethacin thiazides

Fasting glucose >126mg/dL on several occasions is diagnostic of diabetes.

  • Postprandial blood sugar

2-hours fast after the last meal, water intake is accepted.  Serum 

 Assay immediately

The same as above

Donot discontinue the anti-diabetic therapy

  • Random blood sugar

No fasting. Serum.

Assay immediately

The same as above

 

  • Glycated Hb (HbA1C)

 EDTA blood

No fasting is needed

Do not discontinue anti-diabetic treatment

 

Monitor the control of diabetes for the last

 4-6 weeks

  • Oral glucose tolerance test

8-14 hrs fast, water intake is accepted. Fasting serum sample + urine sample Give the patient 100g glucose load in 250-300 water

serum sample  + urine sample are taken after 1-, 2-, and 3-hours thereafter

The same as fasting blood glucose

Fasting glucose >126mg/dL on several occasions is diagnostic of diabetes & OGTT is not needed for the diagnosis

  •           Fructosamine assay

No fasting

Serum sample

Do not discontinue anti diabetic therapy

 

Monitors the control of diabetes over the last 2-3 weeks

Renal Function Tests

 

 

 

  • Blood urea nitrogen (BUN)

No fasting required

All renal functions require serum sample

Avoid hemolysis

Corticosteroids, thyroxin, chloramphenicol,streptomycin,protein intake

Increase with age

  • Serum creatinine

 

Ascorbic acid, methyl dopa, lipaemia

More specific and sensitive than BUN

  • Serum uric acid

 

Salicylates, nicotinic acid, corticosteroids, methyl dopa, caffeine, theophylline, diuretics,purine rich diet(liver-kidney)

 

  • Na

 

 Androgens,, oral contraceptives, diuretics,hyperglycemia corticosteroids,heparin,vasopressin,reserpine

Monitored 2-3 hrs following therapy

  • K

 

Antineoplastic agents,heparin,endomethacin, isoniazide,lithium,penicillin,spironolactone, tetracyclins,corticosteroids,diuretics salicylates

Monitored 2-3 hrs following therapy

  • Total calcium (Ca2+)

 

Androgens,diuretics, oral contraceptives, anticonvulsants,corticosteroids.

Tetany may occur with normal serum total calcium due to decreased ionized calcium

Sample taken in a plastic tube, to be corrected if albumin is low

  • Phosphorus (Ph)

 

Androgens,growth hormone, oral contraceptives,bilirubin,anaestheticsinsulin, anticonvulsants,aspirin.

 

  • Chloride

 

Hyperlipidemia

 

 

  • Creatinine clearance

24 hr urine collection or any other timed urine collection e.g., 2hr;

  serum sample .

 

Should be corrected according to body surface area

  • Microalbuminuria (screening)

24 hrs urine +morning sample (no preservative)

 

Used to follow up diabetic patients

  • Microalbuminuria (Quuant.)

24 hrs urine +morning sample (no preservative)

 

 

 

  • Vanillylmandelic acid (VMA) in urine

24 hrs urine with no preservative

Coffee, tea, chocolate, vanilla, banana, methyl dopa, vasopressors

Diagnosis of pheochromo- cytoma

Liver Function Tests

 

 

 

  • Alanine aminotransferase (ALT, SGPT)

No fasting required

Serum sample

Hepatotropic drugs ,Intramuscular injections

 

  • Aspartate aminotransferase (AST, SGOT)

No fasting required

Serum sample

Markedly increase in fulminant hepatitis (AST>ALT), with ampicillin, erythromycin

 

  • Direct bilirubin

No fasting required

Serum sample(avoid exposure to light)

 

 

  • Alkaline phosphatase

No fasting required

Serum sample

Increases by standing at room temperature or refregeration

 

  • Lactate dehydrogenase (LDH)

No fasting required

Serum sample

 

 

  • Gamma-glutamyl transferase (GGT)

No fasting required

Serum sample

Increases with barbiturates, alcohol intake and phenytoin.

In acute hepatitis it indicates recovery when returns to normal

  • Total protein

No fasting required

Serum sample

 

 

  • Serum albumin

No fasting required

Serum sample

Increases with ampicillin and prolonged tourniquet use. Decreases with oral contraceptives,aspirin, sulfonamides and bilirubin

 

  • Amylase

No fasting required

Serum sample

Increases with narcotic analgesics, oral contraceptives, sulphonamides and thiazides.

 

  • Serum protein electrophoresis

No fasting required

Serum sample

 

Used for screening and follow up of multiple myeloma.

Lipid Profile

 

 

 

  • T. Cholesterol
    • Fasting for 12 -14 hours is mandatory for triglycerides, but optimal for other tests
    •  serum sample
    • LDL is calculated using a special formula only if the TG is
 

 

 

  • · HDL-Cholest.

 

 

 

  • · LDL-Cholest.

 

 

 

  • · Triglycerides

 

 

 

Cardiac Enzymes

 

 

 

  • Creatine phosphokinase (CK)

No fasting required

Serum sample

Avoid hemolysis

Increases with IM injection, returns to normal after 48 hrs after myocardial infarction.

 

  • CK-MB

No fasting required

Serum sample

Avoid hemolysis

Atypical macromolecules may cause falsely high or low results

Diagnostic for acute myocardial infarction.

  • AST

No fasting required

Serum sample

Avoid hemolysis

Liver diseases

 

  • LDH

No fasting required

Serum sample

Avoid hemolysis

 

Infectious mononucleosis

Markedly elevated in untreated pernicious anaemia

HORMONES

 

 

 

  • Β-HCG (qual. quant.)

Serum sample

Centrifugation should be done after strong clot is formed

Doubles every 48 hrs in pregnancy.

Rheumatoid factor give false positive result

False positive results with hemolysis and lipemia

  • Cortisol 9am/9pm/ urine*

Serum sample

24 hrs urine with no preservative

Increases with heavy smoking

 

  • DHEA-S

Serum sample

 

Stored frozen within 1 hour

  • Estrogen E2 (Estradiol)

Serum sample

Menstrual cycle phase, contraceptive pills.

 

  • Free T3

Serum sample

 

Used for follow up in first month following thyroidectomy, then continue with TSH thereafter.

  • Free T4

Serum sample

 

The same as free T3

  • FSH

Serum sample

Menstrual cycle phase

 

  • Growth hormone (GH)

Serum sample (Fasting and basal)

exercise , insulin ,glucose

Refrigerate sample immediately.

.To detect deficiency use stimulation tests

  • Luteneizing hormone (LH)

Serum sample

Menstrual cycle phase

 

  • Parathormone (PTH)

Serum sample

 

 

  • Prolactin (PRL)

Serum sample

 

 

  • TSH

Serum sample

 

To diagnose thyroid disease routinely do TSH & free T4 only.With high TSH and normal freeT4 proceed to freeT3.

Used for follow up of hypothyroid pts. 3 months after starting therapy and every … thereafter.