Medical Laboratory Technician Exam Blood Bank and Transfusion 2 — Questions and Answers
Question 1: A patient with anti-K antibody needs a transfusion. Which percentage of random donors are Kell-negative?
- About 9%
- About 50%
- About 91% (Correct answer)
- About 99%
Correct answer: About 91%
Approximately 91% of the population is K-negative (kk genotype), making compatible blood relatively easy to find.
Question 2: Which phenotype is known as the 'Bombay phenotype' and lacks H antigen on red cells?
- O negative
- Oh (hh) (Correct answer)
- A2 subgroup
- Le(a-b-)
Correct answer: Oh (hh)
The Bombay phenotype (Oh) lacks the H antigen due to homozygous h/h, making individuals incompatible with all ABO groups.
Question 3: A DAT is positive with anti-IgG but negative with anti-C3d. This pattern is most consistent with:
- Cold agglutinin disease
- Drug-induced immune hemolysis (drug adsorption) (Correct answer)
- ABO hemolytic disease of the newborn
- Paroxysmal cold hemoglobinuria
Correct answer: Drug-induced immune hemolysis (drug adsorption)
Drug adsorption (hapten) mechanism coats RBCs with IgG drug antibodies, yielding a DAT positive only with anti-IgG reagent.
Question 4: Which irradiation dose is used for blood components to prevent transfusion-associated graft-versus-host disease (TA-GvHD)?
- 500–1,000 cGy
- 1,500–2,000 cGy
- 2,500 cGy minimum (Correct answer)
- 5,000 cGy
Correct answer: 2,500 cGy minimum
A minimum of 2,500 cGy (25 Gy) delivered to the midplane inactivates donor lymphocytes and prevents TA-GvHD.
Question 5: In an antibody identification panel, an antibody reacts with all cells except those negative for a single antigen. This pattern indicates:
- Multiple alloantibodies
- An autoantibody
- A single alloantibody to that antigen (Correct answer)
- A dosage effect
Correct answer: A single alloantibody to that antigen
Reactivity with all antigen-positive cells and non-reactivity with antigen-negative cells defines a single alloantibody to that antigen.
Question 6: Platelets stored at room temperature (20–24°C) have a maximum shelf life of:
- 3 days
- 5 days
- 7 days with pathogen reduction (Correct answer)
- 14 days
Correct answer: 7 days with pathogen reduction
Standard platelets expire in 5 days, but pathogen-reduced platelets with secondary rapid testing may be stored up to 7 days per FDA guidance.
Question 7: A neonate is found to have anti-c in maternal serum. Which Rh phenotype should be selected for exchange transfusion?
- R1R1 (CDe/CDe) (Correct answer)
- R2R2 (cDE/cDE)
- rr (cde/cde)
- R0r (cDe/cde)
Correct answer: R1R1 (CDe/CDe)
R1R1 (CDe/CDe) units are c-negative and will not be destroyed by maternal anti-c crossing the placenta.
