MLT GlobeDHA exam preparation (Dubai) – page 12
700 practice MCQs for the DHA medical laboratory exam. Level: Basic to intermediate.
A patient has multiple refractory peptic ulcers and diarrhoea. Which fasting serum hormone would be greatly raised?
A gastrinoma (Zollinger–Ellison syndrome) greatly raises gastrin and acid output. A paradoxical rise in gastrin after secretin confirms it.
In the testis, which hormone acts on Sertoli cells to make androgen-binding protein?
FSH stimulates Sertoli cells to make androgen-binding protein and inhibin B, which support spermatogenesis. LH acts on Leydig cells to make testosterone.
Which hormone pattern is typical after menopause?
Without ovarian follicles, estradiol and inhibin fall, so FSH (more than LH) rises through loss of negative feedback.
A patient with flushing, diarrhoea and a liver mass is suspected to have a midgut carcinoid tumour. Which urine test is used?
Carcinoid tumours make serotonin, which is metabolised to 5-HIAA. Bananas, walnuts and some drugs can falsely raise results.
Compared with amylase, serum lipase in acute pancreatitis is:
Lipase comes mainly from the pancreas, whereas amylase is also made by salivary glands. Lipase rises in 4-8 hours and stays high for 8-14 days, longer than amylase, which normalises within 3-5 days.
A thin blood film shows many small ring forms, some with two chromatin dots, in normal-sized red cells, plus crescent (banana)-shaped gametocytes. The species is:
P. falciparum shows multiple small rings, double chromatin dots and appliqué forms in unenlarged cells; its gametocytes are crescent shaped. Mature stages are usually absent from the blood.
A man develops hemolysis after taking primaquine. A supravital stain shows Heinz bodies and the smear shows 'bite' cells. The most likely cause is:
G6PD-deficient cells cannot make enough NADPH to protect hemoglobin from oxidation. Oxidant drugs or fava beans denature hemoglobin into Heinz bodies, which the spleen 'bites' out.
Which tumour marker is mainly used to monitor recurrence of colorectal cancer after surgery?
CEA is not good for screening but is useful after resection: a rising level suggests recurrence. AFP is used for hepatocellular and germ cell tumours, CA-125 for ovarian cancer and PSA for prostate cancer.
In the Ziehl-Neelsen stain, the primary stain and decolouriser are:
Heated carbol fuchsin enters the waxy mycolic acid wall; acid-alcohol cannot remove it from mycobacteria, so they stay red against a methylene blue counterstain.
A serum is diluted 1:10, and that dilution is then diluted 1:5. The final dilution is:
Serial dilutions multiply: 1/10 × 1/5 = 1/50. Multiply the measured result by 50 to get the original concentration.
A blood gas sample was left at room temperature for 60 minutes before analysis. Which change is expected?
Leukocytes and other cells continue to consume O2 and produce CO2 and lactate, so pO2 and pH fall while pCO2 rises. Capping prevents air exchange but not metabolism.
A plasma glucose of 126 mg/dL is equal to approximately:
To convert glucose from mg/dL to mmol/L divide by 18 (126 / 18 = 7.0). 5.6 mmol/L equals 100 mg/dL.
Which method measures osmolality most commonly in clinical laboratories?
Freezing point depression osmometers are most widely used and detect volatile solutes such as ethanol and methanol. Vapor pressure osmometers do not detect volatile alcohols.
During heme breakdown in macrophages, which enzyme opens the heme ring to form biliverdin?
Heme oxygenase cleaves the heme ring, releasing iron and carbon monoxide and forming biliverdin; biliverdin reductase then forms bilirubin. Ferrochelatase inserts iron during heme synthesis.
The biuret method for total serum protein is based on which reaction?
In biuret, Cu2+ in alkaline medium binds peptide bonds (at least two per molecule) to give a violet colour read near 540 nm. Nitrogen conversion to ammonium is the Kjeldahl method, not biuret.
Which plasma protein decreases during the acute-phase response?
Transthyretin, albumin and transferrin are negative acute-phase proteins and fall during inflammation. CRP, fibrinogen and haptoglobin are positive acute-phase reactants.
After starting a fixed dosing schedule, a drug reaches steady state after about:
After about 5 half-lives, the amount given equals the amount eliminated (about 97% of steady state). TDM samples are usually taken after this point.
Serum iron is 45 µg/dL (8 µmol/L) and TIBC is 450 µg/dL (80 µmol/L). What is the transferrin saturation?
Transferrin saturation = serum iron ÷ TIBC × 100 = 45/450 × 100 = 10%. A value below about 16–20% suggests iron-deficient erythropoiesis.
Fine, dark blue-black granules are scattered over cells and the background of a Wright-stained smear. The most likely cause is:
Precipitate appears on and between cells and in the background, which true intracellular inclusions do not. Filtering the stain and proper washing prevent it.
Which peripheral blood picture is most typical of chronic-phase chronic myeloid leukemia?
Chronic-phase CML shows marked leukocytosis with a full spectrum of maturing granulocytes (myelocyte and segmented peaks) and basophilia. Toxic changes point to infection, not CML.