We have a patient who recently typed 1+ with anti-D reagents (both Gamma-clone, monoclonal blend and Ortho Bioclone, Mono-poly blend). Following guidelines that others have suggested (if less than 2+, interpret as Rh neg) we called her Rh neg and transfused Rh neg units.

Later, after investigating some more, we discovered some old (precomputerization) records of 3+ reactions with anti-D (we were using the same Gamma-clone at that time, I think). The patient was transfused at that time with Rh positive units. She did not make any anti-D (at least nothing we are detecting now).

The patient has been diagnosed with myelodysplasia since the old testing. Could this disease state be altering the expression of D antigen on her red cells? Antigen typing for E also showed just 1+ reactions.

Would you transfused this patient with Rh positive blood or stick with Rh negative?

Linda Frederick

We had an oncology patient once that had a weakening of D antigen and at the time I read up on it and found that this situation had been documented in the past. I don't remember any details.

It seems what to give could be argued either way so I will stand back and let wiser heads prevail.

I'm curious to know where these guidelines regarding Anti-D levels of less than 2+ came from. Is this AABB, CAP, etc?

I've had this happen as well, and in these cases I've given Rh negative units if at all possible if only for the fact that a person on chemo probably shouldn't be exposed to any more RBC antigens than they need to be. If my inventory allows me to give immunocompromised patient RH negative blood, then I'll give it. However, these patients are still producing a detectable level of Anti-D so it would seem like Rh pos blood should be fine.

We have a patient we've been transfusing for years that has a type of myeloproliferative disorder in which she now had no Anti-D titer. She started off as a B Positive, but for all intents and purposes she is now a B Negative and we give her Rh negative units.

So I guess it all depends on the patient's situation, but we've done it both ways.

John Judd has submitted articles on this subject, and I believe he personally uses 2+ as a cutoff for Rh negative assignment (in other words, the reaction must be 3+ or stronger, or the patient is classified as Rh negative.) But there are no official guidelines or regulations on this issue. The whole idea is to prevent Rh immunization in cases where the patient's safety could be compromised, such as where the issue of HDN arises in women of childbearing age. Does this patient have any intentions of having more children? If not, your level of concern may drop. We always look at this issue on a case by case basis.

I agree that the patient's status could cause a weakened expression or a blocking of the D antigen.

BC

The weakened reactions due to disease states should not represent a person becoming a partial D and thereby being at risk of making anti-D to the missing parts. That would be genetically determined. As long as the immune system sees D antigen as "self" it won't make anti-D, no matter how little antigen is on the red cells.

In Geoff Daniels's Human Blood Groups SECOND EDITION

page 250 has said "Abnormal expression of some Rh antigens has occasionally

been observed in patients with myeloid

leukaemias, polycythaemia, and other myeloproliferative

disorders. In most cases these patients appear to

be mosaics with two populations of red cells of different

Rh phenotype [137,656–661], although a few

have complete loss of certain Rh antigens [662–665].

One patient with myeloid metaplasia, previously

known to be D+ , was found to be D– and had made

anti-D plus -C [663]."

663 Cooper B, Tishler PV, Atkins L, Breg WR. Loss of Rh

antigen associated with acquired Rh antibodies and a

chromosome translocation in a patient with myeloid

metaplasia. Blood 1979;54:642–7.

Thanks Shily. I happened to read the same item in Human Blood Groups--after I made the post. I stand corrected. Isn't the immune system an amazing thing? "Who'da thunk" that the body could forget "self" and start making antibodies to antigens it previously had. I wonder if the reported case was an aberration--although I guess Lewis antibodies often work like this.

This topic was discussed at length 2 weeks ago on an AABB audioconference presentation. The majority of the people responding use a 2+ in tube and a 3+ in Gel as cut off points to determine Rh. You should be able to find this audioconference recorded on-line I believe. (AABB) I will see if I can find and list link here. I'm a straight-up donor center guy and was freaking out until I realized they were talking about PATIENTS not DONORS.....funny how that changes all of your thinking on somethings. The discoussion about Anti-D being made to only small parts of the antigen were interesting. We have a donor that is I.S. 3+ D, but has an antibody with neat looking doseage.