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RhD status

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Hi 

We had antenatal patient where her Rh D status was negative at booking blood. She was also Rh D neg in her first pregnancy.   Now we received dsample where is reacting as a weak D positive we received 3 subsequent sample to exclude WBIT. Sample sent to reference lab and reported as weak D positive.  It is confirmed by reference lab weak D positive not partial D.

We have nearly 10 historical group where she was Rh D neg.  How could it be changed.? 

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I wouldn't mind betting that, either your anti-D reagent has changed, or the technology used has changed, or both.

The monoclonal anti-D reagents are blended so that certain epitopes of the D antigen are detected, and some are not.  These blends may change over time, even from the same supplier, but, if you have changed supplier, you may have a different blend altogether.

Then the technology could have changed from tube (or whatever) to, perhaps, CAT - there are different sensitivities with each technology.

Has the woman got the R2 haplotype?  By that, I mean is she an R2r with a weak D?  The reason I ask this is because Weak D Type 2, which is associated with the R2 haplotype can be expressed really, really weakly sometimes, and this may explain why the woman has been classified as D Negative in the past.

Just a bit of Sunday afternoon musing on my part!

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Yes, Weak D Type 2 can be a real challenge some times!!!!!!!

You should treat her as D Positive (see Daniels G.  Variants of RhD - current testing and clinical consequences.  British Journal of Haematology 2013; 161 (4): 461-470.  doi: 10.1111/bjh.12275).

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On 03/07/2016 at 2:05 PM, Malcolm Needs said:

Yes, Weak D Type 2 can be a real challenge some times!!!!!!!

You should treat her as D Positive (see Daniels G.  Variants of RhD - current testing and clinical consequences.  British Journal of Haematology 2013; 161 (4): 461-470.  doi: 10.1111/bjh.12275).

I attended NEQAS meeting yesterday and they were mentioning that if patient is Weak D type 4, 11 ,15 ,21 ,57 they can make allo anti-D. I am bit confused 🤔. I know if patient are variant D such as DIII, IV V ........ can develop anti-D. But I wasn't aware of about subtype of Weak D and they actually can develop antiD

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There are lots of mutations now known which cause weak expression of the D antigen. Patients who have been found to be weak D, which traditionally wasn't associated with the production of alloanti-D have gone on to make alloanti-D, so the old adage of "weak D's don't make anti-D and partial D's do" does not hold water any more. As Malcolm states, Geoff Daniels' paper above describes the situation perfectly. Current BSH guidelines state that if the patient is found to be a weak D type 1,2 or 3 then they are to treated as D positive, as the evidence behind alloanti-D production in these weak D phenotypes is limited, and flawed in many cases. Therefore ANY OTHER WEAK/PARTIAL D should be called a D variant, and treated as D negative. 

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We've seen the blood group "change" from D negative to D positive during the course of the pregnancy on a couple of occasions...using the same reagents and technology and confirmed as weak D positive by NHSBT Filton.  As Malcom suggests, they typed as R2r.

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Letty, PLEASE review your nomenclature!  An individual CANNOT be "weak D positive" (even if Filton's NHSBT has tested the sample) because there is no such thing as anti-weak D!  The early workers, such as Fred Stratton, Rob Race, Ruth Sanger and Sylvia Lawler performed over 20, 000 tests between 1946 and 1948 trying to separate anti-D from (what they then called) anti-Du, and failed!  Your patient is D Positive and expresses a Weak D Type 2 antigen.

Sorry, correct terminology is a hobby of mine :blahblah::blahblah::blahblah::blahblah::blahblah:!!!!!!!!!!!!!!!!!!!

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