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;
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.
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