A 60 year old man is admitted into the ER. He has a history of colon cancer. Some blood is drawn from him for lab tests:

His blood culture came up positive for E. coli.

His hemoglobin is : 8.1 g/dl

His ABO RH is:

Anti-A= 4+

Anti-B=0

Anti-D=4+

a1 cells= 2+

b cells= 4+

What could be the explanation for this discrepancy?

Here is what I answered:

Patient possibly have sub-group other than A1 cells, perhaps A2.

I test commercial A2 cells with patient's serum. Then test patient cells with anti-A1 lectin. If both tests are negative, then patients cells are A subgroup other than A1.

So his blood type is A+.

Did I miss anything? I am just wondering why the E.coli part was added to the question. It is known that gram negative bacteria can modify the A antigen to a B antigen, and I was thinking maybe this was a B antigen phenomena question, but then, that would have mean, forward typing would have been positive for B antigen. Maybe that E.coli thing was thrown in there to confuse things. Thanks.

I think you are right.

Hi trisam,

I am with you... I think the e coli is to confuse you. I would first investigate if the patient was group A2 with anit-A1. It is fast and easy. I hope we.....uh ... I mean you get an A on your test.

JB

I think you're correct that the patient is an A2 with anti-A1, but to confirm that you might want to run an antibody screen under the same conditions that you tested your A1 and A2 cells. If negative, this will eliminate the possibility that the patient has some other IgM antibody (anti- P1, M, N etc) directed against an antigen (other than A1) found on the A1 cells but not the A2 cells.

Yes, I agree that the patient was A2 with anti-A1. If the anti-A1 is not reactive at 37C, transfuse the patient with group A red cells if your hospital uses computer crossmatch. However, if the anti-A1 is reactive at 37C (not common) and/or your hospital uses abbreviated crossmatch (perform IS to countercheck ABO group), then give group O cells to the patient.

Hope that helps.

CK Cheng, MSc, SBB(ASCP), CQA(ASQ)

Dec 29, 2009