We have a patient who has undergone a BM transplant (patient originally group O, now been given BM from an A donor). His group is coming up mixed field but this is because we are still transfusing him with O blood every 7 days or so. My question is how can we tell when he has completely transformed to his new blood group (A) when he keeps having O blood? We would like to give him his new group but not sure what the next step shoud be?

I would wait for his back type to no longer exhibit anti-A. (i.s. and ahg).

Stated in another way, when full crossmatches with Group A donor units are compatible.

Thanks guys!

You can monitor this patient's retic count. When it starts to come back up it is a sign of engraftment, the new marrow is now producing RBC's.

A call to the transplant physician is always helpful, they can give you an indication of how the patient is fairing post transplant.

The other thing you could do, but not easily, is molecular work on the white cells, to see if they are recipient or donor derived.

It can take up to 4 months for rbc production to be completely swapped over and isoagglutinin titers to reflect only the new population of cells. Delayed rbc engraftment is most often seen in nonmyeloablative allogeneic transplants. It is possible for someone to be wbc fully engrafted by RFLP/Fish but still have old populations of mature recipient plasma cells circulating making the old ABO antibodies, so wbc chimerism studies are helpful but not the full story. From a practical standpoint L106's suggestion of crossmatch compatible is defensible. At our institution for simplicity and caution we usually just wait until the front type is no longer mixed field (Most patients dont continue to use rbc for longer than a couple months post transplant unless they relapse or under certain anti-viral drugs) and the old back type is no longer showing. Formation of new backtype antibodies (eg A -> can take even longer since the whole immune system is basically being reconstituted so you probably dont want to specify waiting until that occurs. This policy does mean they have convoluted ABO specific needs for a while longer, but its low risk and doctors love low risk =P

There is a good article in last month's TRANSFUSION, volume 51, June 2011 called 'how do I approach ABO-incompatible hematopoeitic progenitor cell transplantation?' by jennifer daniel-johnson and joseph schwartz. It is more transplant-side geared rather than from the BB standpoint but its a good overview of the underlying process.

We give blood that is compatible with the patient's current back type and plasma that is compatible with the patient's current front type.