MLT GlobeDHA exam preparation (Dubai) – page 14
700 practice MCQs for the DHA medical laboratory exam. Level: Basic to intermediate.
Dengue, Zika and chikungunya viruses are mainly transmitted by which vector?
Aedes aegypti (and Aedes albopictus) spread all three viruses. Culex mosquitoes mainly spread West Nile and Japanese encephalitis viruses.
A 10-month-old has severe watery diarrhea during winter. Which test is commonly used to detect the most likely viral cause?
Rotavirus is a major cause of severe infant gastroenteritis. Large amounts of virus are shed in stool, so antigen detection by immunoassay or molecular testing is used.
Normal CSF glucose is approximately what fraction of the plasma glucose?
CSF glucose is normally about 60–70% of plasma glucose, so a plasma sample should be drawn at the same time. A ratio below about 0.4 suggests bacterial, fungal or TB meningitis.
A pregnant woman reports fluid leakage. Which result best supports that the fluid is amniotic?
Amniotic fluid is alkaline (pH about 7.0–7.5), turning nitrazine blue, and forms a fern pattern when dried. Vaginal fluid is acidic, and urine has high urea and creatinine.
The reagent strip protein pad is based on which principle?
At a fixed pH of about 3, the indicator (tetrabromphenol blue) changes colour when protein, mainly albumin, accepts hydrogen ions. This is the protein error of indicators.
A patient with hemolytic anemia is expected to have:
Excess unconjugated bilirubin is not water-soluble and does not appear in urine, but more is converted to urobilinogen in the gut and excreted in urine.
A urine specimen kept at room temperature for 6 hours before testing will most likely show:
Bacteria multiply, consume glucose and produce ammonia from urea, raising pH. Casts and cells may also lyse. Urine should be tested within 2 hours or refrigerated.
The protein matrix of all urinary casts is uromodulin (Tamm–Horsfall protein). Where is it produced?
Uromodulin is secreted by cells of the thick ascending limb and distal tubule; casts form in distal and collecting tubules where urine is concentrated. It is not a glomerular protein.
A pear-shaped flagellate with a jerky, rapid movement is seen in a fresh urine from a woman with vaginal discharge. It is:
Trichomonas vaginalis is identified in urine or vaginal fluid by its pear shape and jerky motility; non-motile forms can be confused with WBCs. Schistosoma is seen as terminal-spined eggs.
The pH electrode on a blood gas analyser works by:
The pH electrode is potentiometric: a special glass membrane develops a potential proportional to H+ activity, measured against a reference electrode. Current from O2 reduction is the amperometric pO2 principle.
The formation of glucose from non-carbohydrate sources such as lactate, glycerol and amino acids is called:
Gluconeogenesis makes new glucose from non-carbohydrate precursors, mainly in the liver. Glycogenolysis is the breakdown of stored glycogen to glucose.
Osmolality differs from osmolarity because osmolality is expressed per:
Osmolality is osmoles per kilogram of water and is what osmometers measure; osmolarity is per litre of solution. The difference matters when plasma water is reduced, e.g. by lipids.
B-type natriuretic peptide (BNP) is mainly secreted by:
Despite its name (first found in brain), BNP comes mainly from the ventricles when they are stretched by volume or pressure overload. Atrial natriuretic peptide comes from the atria.
Total bilirubin is 5.2 mg/dL (89 µmol/L) and direct bilirubin is 0.8 mg/dL (14 µmol/L). What is the indirect bilirubin?
Indirect (mostly unconjugated) bilirubin = total − direct = 5.2 − 0.8 = 4.4 mg/dL (75 µmol/L). A mainly indirect rise suggests hemolysis or reduced conjugation.
The primary structure of a protein is:
Primary structure is the linear amino acid sequence joined by peptide bonds. Helices and sheets are secondary, 3D folding is tertiary, and subunit arrangement is quaternary structure.
In multiple myeloma, the 'CRAB' features stand for hypercalcemia, renal insufficiency, anemia and:
CRAB = Calcium raised, Renal failure, Anemia and Bone (lytic) lesions. These end-organ features separate active myeloma from MGUS and smoldering myeloma.
Creatinine in the blood is formed mainly by:
Creatine phosphate in muscle is converted to creatinine spontaneously at a fairly constant rate related to muscle mass. Purine breakdown produces uric acid, not creatinine.
Urine drug screens for cocaine use detect which main metabolite?
Cocaine is quickly hydrolyzed to benzoylecgonine, which stays in urine for several days and is the target of screening and confirmation. THC-COOH is the cannabis metabolite.
A patient had most of the terminal ileum removed for Crohn disease. Loss of this segment directly impairs absorption of:
The B12–intrinsic factor complex is absorbed by cubam receptors in the terminal ileum. Iron is absorbed mainly in the duodenum and folate in the proximal jejunum.
Which condition most typically produces many spherocytes on the peripheral smear?
In warm AIHA, macrophages remove part of the IgG-coated membrane, producing spherocytes. Liver disease gives target cells, iron deficiency pencil cells, and lead basophilic stippling.