Medical Laboratory Technician Exam Blood Bank and Transfusion 2

Question 1

A patient with anti-K antibody needs a transfusion. Which percentage of random donors are Kell-negative?

Accepted Answer

About 91%

Answer

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?

Accepted Answer

Oh (hh)

Answer

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:

Accepted Answer

Drug-induced immune hemolysis (drug adsorption)

Answer

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)?

Accepted Answer

2,500 cGy minimum

Answer

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:

Accepted Answer

A single alloantibody to that antigen

Answer

Reactivity with all antigen-positive cells and non-reactivity with antigen-negative cells defines a single alloantibody to that antigen.

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