Rh Neg becomes weak D pos

[LAURAA80]

I'm wondering if anyone knows if the Rh expression can vary. We have had 2 patients (pregnant) recently who had a history of being Rh negative that were then showing as weak D positive.

Patient 1: Historically Rh negative 4x. Came in Jan and was weak D positive. Fetal screen also positive. KB stain was negative. This patient came in in April and delivered. Pre and post delivery samples were Rh weak D positive. Fetal screen was positive again and KB was still negative. Baby was Rh Positive. This patient had another pregnancy and the fetal screen was negative approx 2 years ago.

Patient 2: Historically Rh negative. Sept 2010 to Feb 2011 patient was Rh negative. By April, patient was Rh weak D positive. Fetal screen again was positive and KB stain was negative. Baby was Rh positive.

Can Rh change based on pregnancy? Wondering if these patients should have historical RH changed or remain Rh negative. If anyone has any insight about what is happening, I would really appreciate some information. Thanks so much!!!

[Malcolm Needs ☆]

I would suggest that you write to Dr Belinda Kumpel, who works at the International Blood Group Reference Laboratory at Filton, Bristol in the UK, who is doing a study on just this subject. I am at home at the moment, but will post again tomorrow, when I can give you the exact address. Belinda is a very friendly person, who would be only too willing to answer any questions you may have (but, if you are shy, please feel free to use my name as an introduction).

[Mabel Adams]

And then let us know what she said. One thing is to be sure you didn't change reagent vendors in the time between the discrepant results. Anyone that questionable gets to be D neg in my book.

I saw one patient years ago that seemed to change her D type. This would have been when we still did weak D testing on everyone. I can't quite remember which direction she went but she had leukemia and I remember looking it up and finding some evidence that such things could happen in lymphomas and leukemias. I suspect that she went from Pos to Neg, but can't quite recall.

[Malcolm Needs ☆]

Hi,

The full address is,

Dr. Belinda Kumpel,

International Blood Group Reference Laboratory,

NHSBT-Filton Centre,

500, North Bristol Park,

Northway,

Filton,

Bristol,

BS34 7QH,

England.

I hope she is able to help you (and, if she does, as Mabel asks, please post her reply here).

[Deny Morlino]

Perhaps I am looking at this in too simple of a fashion, but here goes. Patient 1 results indicate that there was a fetal maternal bleed to some degree during the recent pregnancy. Patient 2 had the same situation of evidence of a fetal maternal bleed. Both babies were Rh positive meaning that the fetal cells would show as Rh positive even though they are in the maternal circulation. If Patient 1's previous pregnancy mentioned from two years ago was negative for a fetal maternal bleed, I am assuming this patient presented as Rh negative throughout the pregnancy. Is it possible the discrepenancy you are finding is due to fetal red cells being detected in the samples taken from the mothers? This could cause some sort of positive result I would think if the bleed was significant enough. Malcolm, Mabel, anyone else set my warped logic straight please.

[SMW]

If there were fetal cells present, the KB would have been positive. The fetal screen reaction is likely a false positive due to presence of D on the maternal cells. I also would be curious to know if different reagents were in use for these different periods.

[Malcolm Needs ☆]

If there were fetal cells present, the KB would have been positive. The fetal screen reaction is likely a false positive due to presence of D on the maternal cells. I also would be curious to know if different reagents were in use for these different periods.

I agree, and, in addition, for the foetal cells to be detected with the grouping anti-D reagents (even the modern, really strong monoclonal anti-D reagents), it would have to have been some FMH!

[Ajac]

Perhaps it is reagent related. New bottle versus older opened bottle. QC typically will show 4+, but you may see variation when looking at individuals who express much weaker. Also, if one typing sat longer, even slightly at either RT or 37, it could affect typing of a weaker expression.

Just out of curiosity, did you do any other Rh phenotying on these patients? I have seen this type of thing when they were E+ with a really weak D.

[BankerGirl]

We had a lung cancer patient, age 68, who went from O neg to O pos over the course of 8 months. There was no reagent change, and it was a gradual change. We initially thought we were going crazy, and kept her as O Neg and transfused her with O Neg, but when her Rh typing got to be 3+ we finally changed her to O Pos and now she is 4+ positive. No antibodies have developed, and she has been transfused multiple times since then.

Mabel, I am curious if you remember any of your references you found. We have never been able to find an explanation for this change.

[SMW]

Below are some references discussing the change from D positive to D negative and associated with changes to Chromosome 1.

Murdock A, Assip D, Hue-Roye K, Lomas-Francis C, Hu Z, Vege S, Westhoff CM, Reid ME.

RHD deletion in a patient with chronic myeloid leukemia. Immunohematology 2008;24(4):160-4.

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.

Cherif-Zahar B, Bony V, Steffensen R, et al. Shift from Rh-positive to Rh-negative phenotype caused by a somatic mutation within the RHD gene in a patient with chronic myeloid leukaemia. Br J Haematol 1998;102:1263–70.

Singleton BK, Green CA, Avent ND, et al. The presence of an RHD pseudogene containing a 37 base pair duplication and a nonsense mutation in Africans with the Rh D-negative blood group phenotype. Blood 2000;95:12–18.

Wagner FF, Flegel WA. RHD gene deletion occurred in the Rhesus box. Blood 2000;95:3662–8.

Kormoczi GF, Dauber EM, Haas OA, et al. Mosaicism due to myeloid lineage restricted loss of heterozygosity as cause of spontaneous Rh phenotype splitting. Blood 2007;110:2148–57.

[dotahill]

We recently had this problem with 2 pregnant ladies at our hospital. To prevent this happening in the future, we elimanated weak D testing on all patients, excluding newborns and babies. Weak D patients are supposed to be treated as Rh negative patients, i.e. with rhogam and Rh negative products. This elimenates the need to explaining changing blood types!

[Liz]

Newborns should be tested for weak D, for the sake of their D neg moms.

Oups sorry, misread "excluding" ok I agree.

[Brenda K Hutson]

Nope; suspect Weak D due to Positive Fetal Screen but Negative KB. We do not perform Weak D Testing on pregnant women. However, we do often find out that they are Weak D because we end up with a positive Fetal Screen. Also, the Positive Fetal Screen due to Weak D will be macroscopic and a fetal-maternal hemorrhage with that many Rh POS cells (resulting in a macroscopic reaction) would not be compatible with life of the newborn. A positive Fetal Screen due to fetal-maternal hemorrhage will be microscopic.

Brenda Hutson

Perhaps I am looking at this in too simple of a fashion, but here goes. Patient 1 results indicate that there was a fetal maternal bleed to some degree during the recent pregnancy. Patient 2 had the same situation of evidence of a fetal maternal bleed. Both babies were Rh positive meaning that the fetal cells would show as Rh positive even though they are in the maternal circulation. If Patient 1's previous pregnancy mentioned from two years ago was negative for a fetal maternal bleed, I am assuming this patient presented as Rh negative throughout the pregnancy. Is it possible the discrepenancy you are finding is due to fetal red cells being detected in the samples taken from the mothers? This could cause some sort of positive result I would think if the bleed was significant enough. Malcolm, Mabel, anyone else set my warped logic straight please.

[Mabel Adams]

Someone once speculated about why they found a stronger positive KB than they expected based on the condition of the baby and came up with the thought that the baby is continually making blood cells so if a 3rd trimester "slow-leak" fetal maternal bleed were the cause of the strong KB, the baby may have made enough cells to at least partly compensate for the blood loss. This would work best if the baby were ABO compatible with Mom since the baby's cells might circulate for a few months in the mother just as transfused cells do. Of course, we usually assume that most FMH occurs at parturition, but maybe it doesn't always. Mostly I have found it wise never to say "never" in this business.

[Malcolm Needs ☆]

Of course, we usually assume that most FMH occurs at parturition, but maybe it doesn't always.

Indeed it doesn't Mabel. This is why we have introduced universal routine antenatal anti-D immunoglobulin prophylaxis for D Negative pregnant women in the UK, although, of course, they are not forced to have it.

[Liz]

Just for clarification, Fetal Screen refers to: Testing for FMH by the Rosette test, right?

[Liz]

I shall answer that myself: yes it is..I only perform the KB test, not the Fetal screen. But I understand from this thread that : We can have a "Positive Fetal Screen but Negative KB" and that would mean the fetus is Weak D. My question is: How can this help me in the, or change my, management of the mother? In all cases we give prophylactic RhIg. Please elaborate.

Thank you.

[John C. Staley]

I shall answer that myself: yes it is..I only perform the KB test, not the Fetal screen. But I understand from this thread that : We can have a "Positive Fetal Screen but Negative KB" and that would mean the fetus is Weak D. My question is: How can this help me in the, or change my, management of the mother? In all cases we give prophylactic RhIg. Please elaborate.

Thank you.

Sorry Liz but you are a little off. Positive Fetal Screen but Negative KB could mean the Mother is Weak D. Remember KB is looking for fetal cells. Fetal screen is looking for D positive cells.

[Brenda K Hutson]

Yes, at 28 weeks here also..

Brenda

Indeed it doesn't Mabel. This is why we have introduced universal routine antenatal anti-D immunoglobulin prophylaxis for D Negative pregnant women in the UK, although, of course, they are not forced to have it.

[Mabel Adams]

Indeed it doesn't Mabel. This is why we have introduced universal routine antenatal anti-D immunoglobulin prophylaxis for D Negative pregnant women in the UK, although, of course, they are not forced to have it.

Of course. Sorry my "maybe" was misleading. I was thinking of bleeds large enough to cause a pos weak D test without the baby being anemic. The theory of a slow-leak bleed with compensation was the "maybe" part. We started routine antenatal RhIG in the US in about 1983 as I recall.

[Mabel Adams]

For about a year we had to do KB on all our RhIG candidate moms but then Ortho came out with the rosette test kit "Fetal Screen"--around 1984. I feel for anyone doing all these tests by KB. That's very labor intensive! Of course the weak D moms will never interfere--just those with persistent fetal Hgb.

[Liz]

Sorry Liz but you are a little off. Positive Fetal Screen but Negative KB could mean the Mother is Weak D. Remember KB is looking for fetal cells. Fetal screen is looking for D positive cells.

Thank you John, now that makes sense!!!!!

[Deny Morlino]

Someone once speculated about why they found a stronger positive KB than they expected based on the condition of the baby and came up with the thought that the baby is continually making blood cells so if a 3rd trimester "slow-leak" fetal maternal bleed were the cause of the strong KB, the baby may have made enough cells to at least partly compensate for the blood loss. This would work best if the baby were ABO compatible with Mom since the baby's cells might circulate for a few months in the mother just as transfused cells do. Of course, we usually assume that most FMH occurs at parturition, but maybe it doesn't always. Mostly I have found it wise never to say "never" in this business.

This was what I had in mind when I was writing my earlier post. Thought it but did not write it in my post. Thanks for the reply.

[galvania]

I think the idea that these results are due to a foetal bleed are something of a red herring in this case. My guess would be that these are all cases of D variants (either partials or weaks) at the limit of detection with routine anti-D antisera. Then, one of the following would have to occur to explain the difference in results:

1. Change in the manufacturer of anti-D reagent

2. Same manufacturer but different clone

3. Same manufacturer, same clone, but different lot number. It is possible that there may be a very slight batch to batch variation from one lot to the other, not in terms of specificity but in terms of strength, that would not normally be an issue, but might be relevant in these cases

4. As 3, but differences in reactivity due to a minimal decrease in activity as the expiry date approaches

5. Small procedural differences that could lead to a small change in sensitivity of the test

for example:

a. if the test is to be carried out at room temperature, and one day that is 20° and another 30°

b. Slight variations in the strength of the cell suspension used (We had a case here of an external quality control being sent out using a D weak Type V which was EXTREMELY weak. Most labs found it, but one or two called it negative. In ALL cases, the cell suspension was too weak - this is the beauty of gel; you can see this in the print outs of the well images)

c. You don't state which technique you are using, but if this is tube, drop size could be relevant

This list is by no means exhaustive. I am sure you can all think of other relevant factors

The rosetting test is more sensitive, therefore is picking up this extremely weak D.

On the other hand, it could be that the patients are true D negatives and the rosetting test is picking up something non-specific............

Whatever, they definitely need to be treated as D- as patients