MLT GlobeQCHP exam preparation (Qatar) – page 8
749 practice MCQs for the QCHP medical laboratory exam. Level: Intermediate.
In a patient with hepatitis B, a positive HBeAg indicates:
HBeAg is released during active replication and correlates with high HBV DNA and infectivity. Seroconversion to anti-HBe usually shows falling replication.
Hepatitis D virus can infect only people who also have hepatitis B because HDV needs:
HDV is a defective RNA virus that uses HBsAg as its envelope. It occurs as co-infection with HBV or superinfection of a chronic HBsAg carrier.
Daily quality control of anti-A and anti-B typing reagents is done by testing them with:
Each reagent must give the expected positive and negative results with known antigen-positive and antigen-negative cells. O cells alone show no positive reaction.
In a column (gel) ABO test, a mixed-field reaction appears as:
Agglutinated cells stay at the top while unagglutinated cells pass to the bottom, showing two populations. A single top band is 4+; a bottom button alone is negative.
Why are red cells washed at least three times before AHG reagent is added?
Free IgG in residual plasma binds and neutralizes AHG, causing false negatives. Washing does not remove bound IgG.
How does the blood bank confirm that a component placed in the irradiator actually received irradiation?
Radiation-sensitive indicator labels change colour or show a mark when the required dose is reached. They give visual proof for each unit; lab tests are not used for this.
Which component does NOT need to be irradiated, even for a patient at high risk of TA-GVHD?
Freezing and thawing kills lymphocytes in plasma, so FFP and cryoprecipitate do not cause TA-GVHD. Cellular components, especially granulocytes, contain viable lymphocytes and need irradiation.
At the time of issue from the blood bank, which check is required?
Before issue, staff verify the recipient's identification, the unit number, ABO/D groups, compatibility, expiry date, and inspect the unit visually. Retesting is not required.
A woman delivered a healthy baby 4 weeks ago and wants to donate whole blood. The correct decision is:
Donors are deferred during pregnancy and for 6 weeks after delivery, to protect maternal iron stores and health. Previous pregnancy does not cause permanent deferral.
Which skin preparation is widely recommended for the donor venipuncture site?
Chlorhexidine–alcohol reduces skin bacteria that can contaminate the unit, especially platelets. Povidone-iodine is an alternative for donors allergic to chlorhexidine. Alcohol alone is less effective.
After delivery of a D-positive baby, RhIG should be given to an eligible D-negative mother within:
Postpartum RhIG should be given within 72 hours of delivery. If missed, it may still be given up to 28 days, but it is less effective.
About what proportion of donors of European descent are K-negative?
About 9% of Europeans are K-positive, so K-negative units are easy to find. About 99.8% are k-positive.
The M and N antigens are carried on:
M and N differ at amino acids 1 and 5 of glycophorin A. S and s are on glycophorin B.
A young adult with atypical pneumonia develops cold agglutinin hemolysis. The autoantibody usually has which specificity?
Mycoplasma pneumoniae infection is associated with transient anti-I. Anti-i is linked to infectious mononucleosis.
Rh antigens are expressed on:
Rh proteins are erythroid-specific. This is why D-positive platelets cause sensitization only through contaminating red cells.
Rh immune globulin is prepared from:
RhIG is concentrated IgG anti-D fractionated from pooled plasma of immunized donors who have high-titer anti-D. D-positive donors cannot make anti-D.
During rapid infusion of several cold red cell units through a central line, a patient develops a cardiac arrhythmia. The most likely cause is:
Rapid infusion of cold blood can cool the heart and cause arrhythmias. An approved blood warmer should be used for rapid or large-volume transfusion.
What is the usual reference range for arterial pO2 in a healthy adult breathing room air at sea level?
Arterial pO2 is normally about 80–100 mmHg (10.7–13.3 kPa) and falls slightly with age. 35–45 mmHg is the normal arterial pCO2 range.
Which is the most important buffer inside red blood cells?
Hemoglobin, especially deoxyhemoglobin, binds H+ generated when CO2 is converted to bicarbonate, making it the main intracellular buffer in RBCs. Bicarbonate is the main plasma buffer.
A patient found unconscious after an opioid overdose has slow, shallow breathing. Which blood gas pattern is expected?
Opioids depress the respiratory center, causing hypoventilation, CO2 retention and acute respiratory acidosis. Low pH with low HCO3− describes metabolic acidosis.