FRCPath Haem Part 1 MCQ-Transfusion 476
A 27-year-old woman of childbearing potential is known to be group O, RhD-negative with a negative antibody screen. She develops a major obstetric haemorrhage following emergency Caesarean section.
Because of an immediate shortage of O RhD-negative red cells, she receives 6 units of O RhD-positive red cells as part of the major haemorrhage protocol. Once stabilised, the transfusion laboratory considers a red cell exchange procedure to reduce the volume of transfused RhD-positive red cells and prevent RhD alloimmunisation.
Following 1–2 volume red cell exchange, what is the most appropriate step ?
A. Repeat ABO and RhD typing using the indirect antiglobulin technique
B. Kleihauer–Betke test
C. Flow cytometry using an appropriate anti-D reagent
D. Direct antiglobulin test (DAT)
E. Maternal serum antibody screen for Anti-D F. No action required
Answer: C. Flow cytometry using an appropriate anti-D reagent
Explanation
Following an inadvertent large-volume transfusion of RhD-positive red cells to an RhD-negative female of childbearing potential, urgent measures may be required to reduce the risk of permanent anti-D alloimmunisation. In cases where the volume of incompatible red cells is substantial, a 1–2 volume red cell exchange may be performed.
After the exchange, the residual RhD-positive red cell population should be quantified using flow cytometry. This provides an accurate estimate of the remaining RhD-positive red cell volume, allowing the transfusion team to determine the appropriate additional anti-D immunoglobulin dose.
Why the other options are incorrect:
A. Repeat RhD typing: May demonstrate a mixed-field population but is not sufficiently quantitative.
B. Kleihauer–Betke…