What is the possible cause?

 

Patient has a known history of anti -E, always receiving  crossmatch compatible E negative RBCs. Patient's phenotype is E negative. However anti -E is eluted from the red cells. I have seen at least three different patients with known anti -E with episodes of anti -E eluted from the red cells. The most recent patient is known K,  also having episodes of K in the eluate.

 

  - the antibodies in the plasma E or K are strong 2+ reactive, no possible to miss in the crossmatch. We do full gel crossmatch

-the donor units are phenotyped both in the donor center and then again prior to crossmatch in transfusion center.

Hi Carina,

 

The cause is almost certainly a "naturally occurring" (no such thing of course) low level auto-antibody, one mimicking an anti-E and the other mimicking anti-K.

 

I was aware of auto-antibodies mimicking anti-E, but it wasn't until Joyce Poole told me that I became aware of an auto-antibody mimicking an anti-K - I then I found one myself!

Thank you Malcolm for the quick reply.

I was thinking that as well, but not sure how to prove the case. The patient's surely have alloanti -E or -K as well, for these were known long before the eluate showed the antibody specificity.

Could be, but not necessarily.  The immune system plays some nasty tricks on us poor serologists sometimes!

Try to get my head around these tricks.

 

Wash solutions used with some elution kits can cause 'non-specific' uptake of Ig, on to red cells, which can include any alloantibodies that are present. From what I've experienced, anti-K seems to be one of the more commoner specificities affected by this phenomenon. If you did us a kit, for the elution, it would be worth checking the pack insert to see if this is a possibility. An alternative protocol might be given, so it might be worth repeating the elutions.

Warm auto antibodies, when starting out, can mimic Rh autoantibodies. Usually when they come back a week or so later, all cells including the auto are strongly positive.

We use BioRad DiaCidel elution. There is no mentioning of non-specific uptake of IgG. The anti -K in the eluate is same strenth (2+) as in plasma.

Just trying to exhaust the simplest possibilities, was the last wash negative?

Yes it was.