An intro to the interpretation of various laboratory tests.

1. VARIOUS LAB TESTS
INTERPRETATION – AN INTRO.
 Cardiac Disorders (Enzymes)
 Fluid and electrolytes
 Thyroid Function Tests
 Common tests in urine, feces, sputum, and CSF
 Microbiological culture sensitivity (c/s)tests
 Tumour markers

2. CARDIAC ENZYMES
Lactate Dehydrogenase (LDH1 – LDH5)
 Highly distributed throughout the body (high concs. in
heart muscle, skeletal muscle, liver, kidneys, brain, and
RBCs);
 LDH1, LDH2 (mainly in heart);
 LDH3 (lungs);
 LDH4, LDH5 (mainly in liver and skeletal muscles);
 LDH1 and LDH2: ↑es after MI, renal infarction,
megaloblastic anaemia;
 LDH1 is often measured after a suspected MI. Post-MI,
peak serum levels of LDH1 are achieved after 2-3 days
after which it declines over 7 days or more.

3.  LDH2 and LDH3: ↑es after acute leukemia;
 LDH5: ↑es after damage to liver or skeletal muscle;
Creatine Kinase (CK)
 Relatively high concs. in heart muscles, skeletal
muscles, smooth muscles, brain;
 Markedly ↑ed after circulation failure, MI, muscular
dystrophies, exercise, and trauma;
 CK has 2 protein subunits: M and B (which combine to
form 3 isoenzymes BB, MM, and MB).
 Cardiac tissues contain more of the CK-MB
isoenzyme.
 CK-MM (skeletal muscle); CK-BB (brain tissue);
 ↑ed after CK-MB levels indicate myocardial necrosis;

4. Enzymes Rise (hrs.) Peak (hrs.) Falls
CK-MB 4 – 6 12 48 – 72 hrs.
LDH 12 48 – 72 7 days
AST 12 24 48 hrs.

5. Aspartate aminotransferase (AST):
 Formerly known as Serum Glutamic-Oxaloacetic Transaminase
(SGOT);
 Found mainly in the cardiac and hepatic tissues; to a lesser extent
in the skeletal muscle, kidney tissue and pancreatic tissue;
 ↑ed AST levels are seen 8 hrs. post-damage to the heart from MI.
Alanine aminotransferase (ALT):
 Formerly known as Serum Glutamic-Pyruvic Transaminase (SGPT);
 Mainly in the liver; to lesser extent in the heart, skeletal muscles,
and kidneys;
 ALT ↑es less consistently and less markedly than AST post-MI.

6. Cardiac Troponins ( ‘I’ and ‘T’)
 Used in the diagnosis of MI;
 Troponin I (< 1.5 ng/ml; only in cardiac muscle);
 Troponin T (< 0.1 ng/ml; in cardiac and skeletal muscles);
 Troponin T has shown prognostic value in unstable angina and
detecting minor myocardial injury w/ greater sensitivity than CK-
MB.

7. Electrolytes: electrically-charged particles (ions) that are essential
for normal cell function and involved in various metabolic activities.
Fluid overload (circulatory overload): A condition where even after
The body’s fluid requirements are met, the administration or
accumulation of fluid occurs at a rate greater than the rate at which
the body can use or eliminate the fluid.
Protein substrates: Amino acid preparations that act to promote the
production of proteins.

8. BICARBONATE (HCO3
-)
 Very important for acid-base balance of the body;
 To treat metabolic acidosis (seen in severe shock, diabetic acidosis,
severe diarrhoea, severe renal disease and cardiac arrest);
 Oral Sodium bicarbonate is used as gastric and urinary alkalizer;
CALCIUM (Ca2+)
 Vital for functioning of nerves and muscles; blood clotting;
building of bones and teeth;
 To treat hypocalcemia (seen in parathyroid disease);
 Also given for cardiopulmonary resuscitation (after open heart
surgery);
 Adjunct for insect bites and stings to reduce muscle cramping;
 For pregnant women who eat a low-Ca2+ diet.

9. MAGNESIUM (Mg2+)
 In nerve impulses transmission; carbohydrate metabolism;
 Replacement therapy in hypomagnesaemia;
 MgSO4 is used to prevent and control seizures in obstetric patients
with PIH;
 Hypermagnesemia: Excess Mg2+ conc.
POTASSIUM (K+)
 In nerve impulse transmission; contraction of smooth, cardiac and
skeletal muscles;
 Available as KCl and potassium gluconate;
 To treat Hypokalemia;
 Hyperkalemia: Excess K+ conc.

10. SODIUM (Na+)
 To maintain normal heart action; regulate osmotic pressure in
body.
 Available as Normal and Half-normal saline;
 To treat hyponatremia;
 Hypernatremia: Excess Na+ conc.
CHLORIDE (Cl)
 Important to maintain acid-base balance;
 Cl retention is often accompanied by Na and H2O retention.
 Hypochloremia: ↓ed Cl conc.; accompanied w/ metabolic acidosis
or alkalosis; Due to CKD, fasting, diarrhoea, vomiting, diuretic Tx;
 Hyperchloremia: ↑ed Cl conc.; indicates hyperchloremic
metabolic acidosis; Due to ARF, dehydration, excess Cl
administration;

11. BICARBONATE (HCO3-)
 Hypobicarbonatemia: due to metabolic acidosis, RF,
hyperventilation, severe diarrhoea, intestinal fluid drainage, drugs
like acetazolamide;
 Hyperbicarbonatemia: due to alkalosis, hypoventilation,
pulmonary disease, persistent vomiting, excess HCO3- intake,
diuretic Tx;

12. Thyroid-stimulating hormone (TSH)
 Normal range: 0.3 – 5 µU/mL (SI: 0.3 – 5 mU/mL)
 To detect hypothyroidism or hyperthyroidism;
 Is also useful for monitoring Tx for hypothyroidism or
hyperthyroidism;
 Abnormal TSH level should be followed up with further thyroid
testing (free thyroxine).
 TSH should be monitored 6 – 8 weeks after initiation or if a change
in Tx occurs.
 TSH in the normal range indicates a return to euthyroid state.

13. TSH (contd’.)
↑ed TSH:
• indicative of hypothyroidism;
• In patients taking thyroid replacement therapy, an ↑ed TSH
suggests the need for an increase in the dose of thyroid
medication.
• Medications (Metoclopramide and other dopamine antagonists);
↓ed TSH:
• TSH < 0.10 is a/w hyperthyroidism.
• In patients taking thyroid replacement therapy, a ↓ed TSH
indicates the need to reduce the dose of thyroid medication.
• Medications (dopamine, levodopa and glucocorticoids);

14. Total Thyroxine (T4)
 Normal range: 4-12 µg/dL; (SI: 51 – 154 nmol/L)
 Is the predominant circulating thyroid hormone;
 Total serum thyroxine measures both free thyroxine and thyroxine
bound to globulin, albumin, and pre-albumin.
 Only the unbound thyroxine is active.
 T4 levels are a measure of the functional status of the thyroid
gland.
 T4 may also be used to monitor thyroid Tx.
 T4 levels may be affected by conditions that ↑ or ↓ the thyroxine-
binding proteins.

15. T4 (contd’.)
↑ed T4:
 In hyperthyroidism, pregnancy, hepatitis;
 Medications (estrogen replacement therapy, oral
contraceptives, tamoxifen, and raloxifene);
↓ed T4:
 In hypothyroidism, a/w renal failure, malnutrition, liver disease;
 Medications that compete for T4-binding sites on T4-binding
proteins (salicylates);
 Medications that ↑ T4 clearance (phenytoin, phenobarbital,
and carbamazepine);

16. Free Thyroxine (Free T4)
 Normal range: 0.8–2.7 ng/dL; (SI: 10–35 pmol/L);
 Free T4 is a more accurate reflection of clinical thyroid status (as
total T4 levels can be affected by conditions that alter the amount
of thyroxine-binding proteins);
 ↓ed free T4 (hypothyroidism);
 ↑ed free T4 (hyperthyroidism);
 Medications:
• Amiodarone and iodides may ↑ or ↓ free T4 levels;
• Lithium ↓ free T4 levels;

17. Total Triiodothyronine (T3 or T3)
 Normal Range: 80–200 ng/dL (SI: 1.2–3.1 nmol/L );
 Usually used in Dx of hyperthyroidism, or T3 toxicosis;
 Has little utility in the Dx of hypothyroidism;
 T3 is 3-4x more potent than T4.
 Majority of T3 is formed from deiodination of T4 in kidneys and
liver.
 Total T3 measures both bound and unbound T3.

18. T3 (contd’.)
↑ed T3:
 Hyperthyroidism, T3 thyrotoxicosis (Grave’s disease), and with high
doses of levothyroxine;
 Pregnancy and use of estrogens or oral contraceptives;
↓ed T3:
 a/w hypothyroidism, malnutrition, and anorexia;
 Medications (Corticosteroids and propranolol);

19. Urinalysis (UA)
 Range of laboratory tests that enable the clinician to identify renal
disorders and non-renal disorders.
 UA components: gross appearance; pH; specific gravity (SG);
protein; glucose and ketones; blood; bilirubin; leukocyte esterase;
and nitrites;
Urine (Appearance and Color)
 Normal colour: clear to dark yellow.
 Some cloudiness is normal (due to phosphates or urate).
 Abnormal urine cloudiness (presence of WBCs, RBCs, or bacteria);

20.  Abnormal urine colors:
Red-orange
• presence of myoglobin (from muscle breakdown from seizures,
cocaine, or injuries); Hb
• Medications (rifampin, phenazopyridine, phenolphthalein,
phenothiazines);
• Foods (beetroot, carrots, berries);
Blue-green
• Medications (amitriptyline, methylene blue);
• Pseudomonal infection;
Brown-black
• presence of myoglobin;
• porphyrins from porphyria or sickle cell crisis;
• phenol poisoning;
• rhubarb ingestion;

21. Specific Gravity
 Normal Range: 1.005 – 1.025
 SG indicates the kidneys’ ability to concentrate urine.
 Unusually ↓ SG (kidneys are unable to concentrate urine
appropriately).
 ↓ SG (hyposthenuria): in CKD, DI (diabetes insipidus);
 ↑ SG (hypersthenuria): a/w
• dehydration, CHF, toxemia of pregnancy;
• Syndrome of Inappropriate AntiDiuretic Hormone (SIADH);
• Excretion of radiologic contrast media,
• ↑ excretion of glucose or protein > 2 g/day

22. Urine pH
 Normal Range: 4.5 – 8.0
 Normal urine specimens are acidic (average pH is approx. 6).
 Alkaline urine:
• In certain UTIs (which are caused by urea-splitting organisms
Proteus, Pseudomonas),
• Renal tubular acidosis;
• Medications (acetazolamide, thiazide diuretics);
 Acidic urine: in metabolic acidosis, pyrexia, diabetic ketosis;

23. Urine (Protein)
 Normal Range: 0 – 1 +
 Trace protein in the urine is a common clinical finding (often has
no clinical significance).
 Proteinuria – Repeated positive tests > 150 mg/dL (may be a
marker of renal disease);
 Causes: Diabetic nephropathy, interstitial nephritis, hypertension,
fever, exercise, pyelonephritis, multiple myeloma, lupus, and
severe CHF.

24. Urine (Glucose and Ketones)
 Normal Range: Both (glucose and ketones) should be negative.
 Glucosuria:
• Glucose in urine;
• suggests diabetes mellitus;
• in a known diabetic, it suggests the need for improved glucose
control;
• a/w Cushing disease, pancreatitis;
• Medications (thiazide diuretics, steroids, oral contraceptives);
 Ketonuria:
 Excess amounts of ketones in urine (when carbohydrate
metabolism is altered);
 Causes: Diabetic ketoacidosis (DKA), starvation, high-protein/low-
carbohydrate diets, and alcoholism;

25. Urine (Blood)
 Normal Range: negative to trace;
 Hematuria (Blood in urine) may indicate urinary tract damage.
 Common causes: Infection, nephrolithiasis, malignancies, and
benign prostatic hypertrophy (BPH).
 False-positive results:
• when povidone iodine is used as a cleansing agent before urine
specimen collection;
• Hemoglobinuria, myoglobinuria;
 False-negative results: patients taking high doses of vit.C or
ascorbic acid;

26. Urine (Bilirubin)
 Normal Range: zero to trace;
 Bilirubin in urine – dark yellow or brown colour; appears in urine
before other signs of liver dysfunction appear;
 a/w liver disease (hepatitis), septicemia, obstructive biliary tract
disease.
 False-positive result: Phenazopyridine or phenothiazines;
Urine ( Leukocyte Esterase)
 Normal Range: zero to trace;
 + leukocyte esterase (indicates WBCs in urine);
 a/w infections and/or inflammation of the urinary tract;

27. Urine (Nitrites)
 Normal Value: is negative;
 Gram-negative bacteria are capable of converting dietary nitrates
into nitrites.
 Presence of nitrites in the urine suggests colonization or infection
with gram-negative organisms.

28. Feces (Stool)Analysis:
 Series of tests done on a stool (feces) sample to help diagnose
certain conditions affecting the digestive tract;
 Conditions include infections (parasites, viruses, or bacteria), poor
nutrient absorption, cancers;
 The stool is checked for color, consistency, pH, amount, shape,
odour, and the presence of mucus.
 The stool may be examined for hidden (occult) blood, fat, meat
fibers, bile, WBCs, and sugars.

29. Fecal Occult Blood Test (FOBT):
 To check stool samples for hidden (occult) blood, which may
indicate colon cancer or polyps in the colon or rectum (not all
cancers or polyps bleed); ulcerative colitis, Crohn’s disease;
 If blood is detected through a fecal occult blood test, additional
tests may be needed to determine the source of bleeding.
 FOBT can only detect the presence or absence of blood — it can't
determine what is causing the bleeding.

30. Sputum Culture
 Sputum: thick mucus or phlegm expelled from the lower
respiratory tract (bronchi and lungs) through coughing;
 Bacterial sputum cultures detect the presence of disease-
causing bacteria (pathogens) in people who are suspected of
having bacterial pneumonia or other lower respiratory tract
infections (LRTIs).
 Bacteria in the sample are identified and susceptibility testing is
performed to guide antibiotic treatment.
 Sometimes, a respiratory infection is caused by a pathogen that
cannot be grown and identified with a routine bacterial sputum
culture.
 Other tests, such as an AFB smear and culture, fungal culture,
or viral culture, may be ordered in addition to or instead of a
routine culture.

31. • sputum culture (contd’.)
 The sputum culture, Gram stain(s), and susceptibility testing all
contribute to a report that informs the health practitioner which
pathogen(s) are present and which antibiotic therapies are likely
to inhibit their growth.

32. CSF Analysis

33. Antimicrobial susceptibility testing (AST)
 Laboratory procedure performed by medical technologists (clinical
laboratory scientists) to identify which antimicrobial regimen is
specifically effective for individual patients.
 On a larger scale, it aids in the evaluation of treatment services
provided by hospitals, clinics and national programs for control
and prevention of infectious diseases.

34. Tumor markers (Cancer markers)
 Refer to proteins that are made by both healthy cells
and cancer cells in the body.
 May also refer to mutations, changes, or patterns in
a tumor's DNA.
 Roles of tumour markers testing:
• Plan the cancer treatment; (If tumor marker levels go down, it
usually means the treatment is working).
• To help diagnose the type and stage of cancer;
• To find out if the cancer has spread to other tissues;
• To help predict the likely outcome or course of the disease;
• To see if the cancer has come back after successful treatment
(relapse);
 Egs.: CA 125, CA 15-3, CA 27-29, PSA, CEA

37. THE END

38. FOR YOUR INFO.

40. CSF Analysis