Transfusion Medicine Flashcards

Massive transfusion protocol (MTP) typically uses a ratio of plasma:platelets:red blood cells of approximately:

Answer: 1:1:1

Modern MTPs use a 1:1:1 ratio of FFP:apheresis platelets:PRBCs. This damage control resuscitation strategy minimizes dilutional coagulopathy and improves survival in massive hemorrhage.

The most common immune cause of platelet refractoriness is:

Answer: HLA alloimmunization (anti-HLA class I antibodies)

HLA class I alloimmunization (from prior transfusions, pregnancies, or transplants) is the most common immune cause of platelet refractoriness. HLA-matched or crossmatch-compatible platelets are required for refractory patients.

A patient with a history of heparin-induced thrombocytopenia (HIT) requires cardiac surgery. The most appropriate anticoagulant approach is:

Answer: Use bivalirudin (direct thrombin inhibitor) or delay until PF4-heparin antibodies decline

HIT is caused by IgG antibodies against PF4-heparin complexes, causing thrombocytopenia and paradoxical thrombosis. LMWH cross-reacts with HIT antibodies and is contraindicated. Bivalirudin is the preferred alternative anticoagulant for cardiac surgery in HIT patients.

Neonatal alloimmune thrombocytopenia (NAIT) most commonly involves antibodies against which platelet antigen?

Answer: Human platelet antigen 1a (HPA-1a)

NAIT is most commonly (more than 80% of cases) caused by maternal IgG antibodies against HPA-1a (also called PL-A1 or Zw-a), a platelet-specific antigen on glycoprotein IIIa (CD61). HPA-1a negative mothers (2–3% of Caucasians) may form anti-HPA-1a when exposed to HPA-1a-positive fetal platelets.

Gel (column agglutination) technology in blood banking works by:

Answer: Centrifuging red cells through a gel matrix — agglutinated cells are trapped at the top while unagglutinated cells pellet at the bottom

Gel cards contain microtubes filled with dextran acrylamide gel with or without antiglobulin reagent. During centrifugation, unagglutinated cells pass through the gel and pellet at the bottom (negative result). Agglutinated cells are trapped in or at the top of the gel column (positive result).

An ABO discrepancy is found where the patient forward types as group A but the reverse grouping shows unexpected anti-A reactivity. This is best described as:

Answer: ABO discrepancy requiring investigation — likely a weak A subgroup (A2) with anti-A1

When a patient forward types as group A but serum shows unexpected anti-A reactivity, this is an ABO discrepancy most likely due to a weak A subgroup (A2, A3, Ax, Ael) where some patients make anti-A1. Must be resolved before transfusion.