FRCPath Haem Part 1 MCQs-Transfusion 482
A 29-year-old woman, G2P1, is found to have a positive antibody screen at 12 weeks' gestation. She is D-negative and has no history of transfusion. Antibody identification demonstrates apparent anti-C and anti-D. The anti-C titre is relatively high.
The obstetric team asks whether she should receive routine antenatal anti-D prophylaxis.
The case is referred to the red cell immunohaematology reference laboratory, where further investigation demonstrates that the apparent anti-D reactivity may be due to anti-G, with or without genuine anti-C. There is no convincing evidence of immune anti-D.
Which of the following is the most appropriate management?
A.
Withhold anti-D prophylaxis because anti-G provides protection against D alloimmunisation.
B.
Withhold anti-D prophylaxis because the presence of apparent anti-D indicates that she is already immunised.
C.
Give RAADP and appropriate post-delivery anti-D prophylaxis, while monitoring the pregnancy according to the clinically significant antibody identified.
D.
Give anti-D only after delivery because antenatal anti-D is contraindicated when anti-C is present.
E.
Give prophylactic anti-D only if the fetal genotype is confirmed to be D-positive.
Answer: C — Give RAADP and appropriate post-delivery anti-D prophylaxis
Explanation
This is a classic FRCPath exam trap involving anti-G versus anti-D + anti-C.
Anti-G can mimic anti-D + anti-C because the G antigen is present on essentially all D-positive cells and most C-positive cells.
Therefore:
Apparent anti-C + anti-D → think anti-G.
Importantly, anti-G itself is not anti-D and therefore does not provide evidence that the woman has become immunised against D.
If reference laboratory investigations establish anti-G or anti-C + anti-G without true immune anti-D, the woman remains at risk of subsequently developing immune anti-D.
Therefore she should be offered:
Routine antenatal anti-D prophylaxis (RAADP)
Appropriate post-delivery anti-D prophylaxis if indicated