MLT GlobeQCHP exam preparation (Qatar) – page 4
749 practice MCQs for the QCHP medical laboratory exam. Level: Intermediate.
After A and B, which red cell antigen is the most immunogenic?
D is the most immunogenic non-ABO antigen; a large proportion of D-negative people exposed to D-positive red cells make anti-D. K is next most immunogenic.
Routine antenatal Rh immune globulin for a nonsensitized D-negative woman is usually given at about:
Antenatal RhIG is given at about 28 weeks, because most sensitizing fetal bleeds happen in the third trimester.
Which measure best reduces the risk of TACO in an elderly patient with poor cardiac function?
Slow infusion and giving single units with reassessment limit volume load; diuretics can also help. Male-donor plasma reduces TRALI, not TACO.
HCO3− is 24 mmol/L and pCO2 is 40 mmHg. Which pH is calculated from Henderson–Hasselbalch?
Dissolved CO2 = 0.0307 × 40 ≈ 1.2 mmol/L; 24/1.2 = 20; log 20 = 1.30; pH = 6.1 + 1.3 = 7.40.
pH 7.49, pCO2 28 mmHg, HCO3− 21 mmol/L in an anxious patient. This is:
High pH with low pCO2 is respiratory alkalosis. HCO3− falls only about 2 mmol/L per 10 mmHg in the acute phase, fitting an acute disorder such as anxiety-related hyperventilation.
Compared with whole-blood glucose from the same sample, plasma glucose is usually:
Plasma has more water than red cells, so plasma glucose is about 10–15% (around 11%) higher than whole-blood glucose. The values are not identical.
In a healthy adult, CSF glucose is normally about what fraction of plasma glucose?
CSF glucose is about 60–70% of plasma glucose, so a paired plasma sample is needed for interpretation. Low values suggest bacterial or fungal meningitis.
In a potassium ion-selective electrode, valinomycin acts as:
Valinomycin is a neutral carrier that selectively binds potassium in the membrane, producing a potential related to K+ activity. The reference electrode provides a constant potential for comparison.
Repeated fist clenching during venepuncture with a tight tourniquet most likely causes:
Forearm muscle activity releases potassium locally, raising results by up to 1–2 mmol/L. This is a common preanalytical cause of pseudohyperkalemia.
Which specimen problem gives a falsely high serum phosphate?
Red cells contain more phosphate than plasma, so hemolysis and delayed separation raise results. Marked thrombocytosis can also raise serum phosphate; fasting, heparin plasma and prompt separation do not cause false elevation.
Which result pattern defines subclinical hypothyroidism?
Subclinical hypothyroidism is a raised TSH with free T4 still in the reference interval. Low TSH with normal free T4 and T3 is subclinical hyperthyroidism.
A patient with fatigue and hyperpigmentation has low morning cortisol and very high ACTH. The most likely diagnosis is:
Adrenal gland failure removes cortisol negative feedback, so ACTH rises; high ACTH (with POMC-derived MSH activity) causes pigmentation. Secondary insufficiency has low ACTH and no pigmentation.
One international unit (U) of enzyme activity is the amount of enzyme that converts:
The international unit is 1 µmol/min under defined conditions. The SI unit, the katal, is 1 mol/s, so 1 U = 16.67 nkat.
Which serum enzyme is most falsely increased by in-vitro hemolysis?
Red cells contain LD at many times the plasma level, so even mild hemolysis raises LD markedly. GGT, lipase and amylase are not significant red-cell enzymes.
Apo B-48 is found only in which lipoprotein class?
Apo B-48 is made in the intestine and is carried by chylomicrons and chylomicron remnants. Liver-derived VLDL and LDL carry apo B-100.
In the hepatocyte, bilirubin is conjugated with which substance?
UDP-glucuronosyltransferase 1A1 attaches glucuronic acid to bilirubin, forming water-soluble mono- and diglucuronides. Glycine and taurine conjugate bile acids, not bilirubin.
Why is unconjugated bilirubin not found in urine even when its serum level is high?
Unconjugated bilirubin is water-insoluble and tightly bound to albumin, so it is not filtered. Only conjugated bilirubin, which is water-soluble, can appear in urine.
Jaundice of the skin and sclera usually becomes clinically visible when total serum bilirubin exceeds about:
Adult total bilirubin is normally below about 1.2 mg/dL; visible jaundice usually appears above about 2.5–3 mg/dL. Values between are called latent or subclinical hyperbilirubinemia.
Immunofixation shows a sharp band in the IgA lane and a band at the same position in the kappa lane. The correct interpretation is:
A heavy-chain band and a light-chain band at the same mobility indicate one monoclonal immunoglobulin, here IgA kappa. A free light chain would show a band only in the kappa lane.
Nephrotic-range proteinuria in an adult is generally defined as urine protein greater than:
Nephrotic syndrome features proteinuria above about 3.5 g/day (per 1.73 m²), with hypoalbuminemia, edema and hyperlipidemia. Lower amounts indicate proteinuria but not the nephrotic range.