Disappearing D

[dcubed]

We have a male patient, 80 yrs old with a history of pancytopenia and has a surgery upcoming. His current pre-op specimen types as D neg weak D neg. Nine years ago this patient was here and typed as D pos on more than one sample and was given 4 units of PRBC's. In looking into his history it was found out that he has also been a patient at a neighboring hospital and they have seen this patient's D type go from D pos to weak D pos to negative. Are there any disease states that can cause suppress the production of the D antigen?

[clmergen]

I know that automated instruments and tube testing will give different D typing. What is <2+ in tube will be negative on the Echo.

[Malcolm Needs ☆]

We have a male patient, 80 yrs old with a history of pancytopenia and has a surgery upcoming. His current pre-op specimen types as D neg weak D neg. Nine years ago this patient was here and typed as D pos on more than one sample and was given 4 units of PRBC's. In looking into his history it was found out that he has also been a patient at a neighboring hospital and they have seen this patient's D type go from D pos to weak D pos to negative. Are there any disease states that can cause suppress the production of the D antigen?

According to Marion Reid and Christine Lomas-Francis in The Blood Group Antigen FactsBook 2nd edition 2004, Elsevier Ltd., reduced expression of Rh antigens and Rh mosaicism can occur in leukaemia, myeloid metaplasia, myelofibrosis, and polycythemia.

Are any of these conditions underlying this gentleman's pancytopenia?

Geoff Daniels, in Human Blood Groups 2nd edition 2002, Blackwell Science, cites 4 papers on the subject, including one in which the individual not only no longer expressed the D antigen, but also produced an anti-D. The paper cited was

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: 642-647.

:):)

[adiescast]

For a patient whose D type is weak (w+ to 2+), we have seen that it makes a difference as to whether the tube was spun immediately or not. Differences in habits between techs can cause different results in these patients. A tech who drops the reagents and cells and immediately spins may get a negative result, while a tech who drops the reagents and cells, then brings the patient up on the computer screen or answers the phone before spinning may get a 2+ result. We have had a couple of patients like that this year. There was discussion on another thread about this phenomenon. I believe TimOz suggested that a short incubation period should be considered for D testing.

[Malcolm Needs ☆]

For a patient whose D type is weak (w+ to 2+), we have seen that it makes a difference as to whether the tube was spun immediately or not. Differences in habits between techs can cause different results in these patients. A tech who drops the reagents and cells and immediately spins may get a negative result, while a tech who drops the reagents and cells, then brings the patient up on the computer screen or answers the phone before spinning may get a 2+ result. We have had a couple of patients like that this year. There was discussion on another thread about this phenomenon. I believe TimOz suggested that a short incubation period should be considered for D testing.

This is true adiescast, but there are other "strange phenomena" too, that will cause false negative results.

One of which I am aware is in a D+ patient who has been given D- blood in an emergency. When a sample is taken shortly afterwards, and then centrifuged fairly hard, the D- cells tend to stay near the top, whereas the autologous D+ red cells go to the bottom, because they are slightly bigger, and hence heavier. It then depends upon which part of the packed red cells are sampled as to whether the patient appears D+ or D-.

The same applies, incidentally, to incompatible transfused red cells. These can also layer out after centrifugation, and, once again, it depends from where these red cells are sampled as to whether the DAT is positive or negative.

:eek::eek::eek:

[L106]

That's interesting, Malcolm. I will keep that in mind the next time we see discrepant results between different technologists, etc.

[Malcolm Needs ☆]

That's interesting, Malcolm. I will keep that in mind the next time we see discrepant results between different technologists, etc.

It was originally noticed because of the difference between automation and a human.

The machine usually takes red cells from the top, whilst, for some reason, humans usually take the red cells from the bottom. I know not why!

:):)

[David Saikin]

I try to stay away from the top / don't want to sample any of the buffy coat.

[Malcolm Needs ☆]

I try to stay away from the top / don't want to sample any of the buffy coat.

Very good point David.

:D:D:D

[adiescast]

Whereas an automated probe, having no eyes, must use a detector to sense the cells. It is easy to sense the cell line and difficult to sense the bottom of the tube before you hit it. Probes are so easy to crash!

[dcubed]

Current sample on the patient was tested in Ortho gel card. Previous sample, nine years ago would have been tube testing.

BTW: Ortho Provue samples cells from the bottom of the tube. The intrument is programed to have the probe go to 1mm from the bottom of the sample tube.

[rravkin@aol.com]

Is it possible that this patient being 80 years old and pancitopenic may be immune compromised as well such that there is a significant reduction in Anti-D; ie falling below the sensitivity capability of the testing system?

[Malcolm Needs ☆]

Is it possible that this patient being 80 years old and pancitopenic may be immune compromised as well such that there is a significant reduction in Anti-D; ie falling below the sensitivity capability of the testing system?

I think I can see from where you are coming, but in this case it is the weakening of the patient's D antigen, rather than the weakening of any antibody. The antibodies used would (presumably) be strong commercial antisera.

There are many factors that will affect the expression of the D antigen, including problems with transportation of the mature ploypeptide from the Golgi compartment, and insertion into the Band 3-based macrocomplex in the red cell mambrane.

In the case of a haematological patient, with weakening of the A and/or B antigens, there is speculation that this may be caused by methylation of the ABO proximal promoter (1) and, if this is true, I suppose that the same could happen to an RHD proximal promoter (I am, however, a blood group serologist and NOT an expert in molecular genetics, and so this could be total snake oil!!!!!!!!!!!).

1. Storry JR, Olsson ML. The ABO blood group system revisited: a review and update. Immunohematology 2009; 25: 48-59.

:confused::confused:

[mcgouc]

Gel may be missing a variant of the D antigen. We routinely use gel for our ABO/Rhs, but perform weak D's on the babies of Rh negative moms who test Rh negative in gel to detect those variants. Personally, I have never had one of these weak D's be positive. On the other hand, we recently had an OB patient who typed Rh positive (2+) in gel. Her prenatal work-up had her as a Rh negative and she had received antenatal RhIG. We did a tube weak D and the test was negative. Her baby was Rh positive (4+) in gel. We sent out a KB stain (no fetal cells detected) and gave her another dose of RhIG. I called customer service and they asked me what the pH of my saline was. Woohoo - we use PBS and it is 7. Then they said it must be a variant.

Just wondering - did your patient receive Rh positive blood in the past and is the antibody screen still negative?

Edited March 9, 2010 by mcgouc

[Mabel Adams]

I had a patient once with a hematological malignancy that went from D+ to weak D+ but never completely negative.

Malcolm, I know that reticulocytes are lighter so should centrifuge near the top, but why would the transfused D- cells do the same. I doubt it is because they are D-, is it?. Does RBC storage cause this change in transfused cells? Or is it not density but shape changes? I have worried about this with fetal screens and Kleihauers and wonder if we shouldn't be careful of ever spinning such samples. Wouldn't want all the fetal cells to be at the top and we sample below them.

[Malcolm Needs ☆]

I had a patient once with a hematological malignancy that went from D+ to weak D+ but never completely negative.

Malcolm, I know that reticulocytes are lighter so should centrifuge near the top, but why would the transfused D- cells do the same. I doubt it is because they are D-, is it?. Does RBC storage cause this change in transfused cells? Or is it not density but shape changes? I have worried about this with fetal screens and Kleihauers and wonder if we shouldn't be careful of ever spinning such samples. Wouldn't want all the fetal cells to be at the top and we sample below them.

To be perfectly honest Mabel, I don't know why it happens; I just know that it does!

That having been said, the phenomenon only lasts for a short while, and so I would think that it must be some sort of reversable storage lession.

:confused: