Hello Everyone,

I've recently had a puzzling experience with a Crossmatch. We've had a patient who has had a history of an anti-E. She was given 3 units of Crossmatch compatible blood, emergency release red cells, in the ER. She presented with a hemoglobin of 4 and the ER physician did not want to wait until we determined whether or not she had developed an additional alloantibody. To make a long story short, one of the units she received was E positive. However, that particular unit was compatible at IS and AHG in gel (LISS) as well as in tube (albumin). Does anyone have an explanation as to why this unit would be compatible if she clearly still demonstrates the antibody, and the unit was antigen positive?

1.Maybe because dosage effect, her antibody is react with homozygous E antigen, and the donor is Ee.

2.Forgive my poor English, I don't know if this specimen you find the anti-E , if not, this because the antibody disappear or under test level , so the crossmatch is compatible.

It could also be that, as there are numerous molecular backgrounds to the E antigen (albeit that the "main" amino acid residue involved in the expression of the E [and e] antigens is a single substitution at position 226 of the mature polypeptide), the E antigen expressed on the red cells of this particular unit may not have been "recognised" by the patient's polyclonal anti-E, but was "recognised" by the anti-E used for grouping.

A long shot, I must admit (I know, I know, hooves and zebras!!!!!!), but still a possibility.

So I assume that the patient did not have an adverse Transfusion reaction...?

Nope. She tolerated it well.

Malcolm is right again!

I have been accused of looking for unicorns when I hear hoofbeats, not just zebras...