Weak D expression query.

[kingkenny1987]

Hi I have just found this site and am very excited!

Anyway I'm a recent graduate just starting in a hospital bloodbank. Today I was asked a question that I just cant answer! I would be very grateful if you guys could help!

So the question was if a patient previously had a weak D expression but now is Rhesus negative, how is this possible.

Thanks again guys and look forward to using this site!

[Malcolm Needs ☆]

It can happen, very rarely, in cases of haematological oncology, but it is much more common for the mixture of clones to have been changed by your supplier, or, that this patient is, infact a Partial DVI, and the original anti-D reagents detected this, but the present ones do not.

[David Saikin]

OR - previously your institution carried Rh= pts through to Weak D testing and now does not . . . we run across this occasionally when an OB pt comes to our hospital to deliver but the prenatal work is done at a local hospital which still performs weak D testing.

[Dr. Pepper]

OR there was an error in specimen ID or test performance. (Why is it always the old specimen, long gone, that seems to have been in error when you have a typing discrepancy?)

[Mabel Adams]

Or you are doing only immediate spin testing and one tech takes a phone call between adding the anti-D and reading the reaction and another reads it as soon as possible (tube testing of a relatively weakly reacting D that sometimes reacts at immediate testing.)

[EDibble]

I was thinking the same thing David, as that is what our institution did.

[kingkenny1987]

Thanks for the replies! You have certainly answered my question.. appreciate it!

[carolyn swickard]

It can happen, very rarely, in cases of haematological oncology, but it is much more common for the mixture of clones to have been changed by your supplier, or, that this patient is, infact a Partial DVI, and the original anti-D reagents detected this, but the present ones do not.

We are using Immucor's reagents Anti-D Series 4 and Series 5. Can you really rely on these reagents to now detect Weak Ds I-V (quanitative weak D - I know this is old terminology, but it works) with immediate spin tests and to NOT detect Partial D VI (qualitative weak D)?? How do they work if you continue through to DU testing - still positive for I-V and negative for VI? Does anyone routinely test their "weak Ds" genetically now to determine real "partial Ds" that could make anti-D? If so, who does this testing in the US?

We are still testing through to AHG on D negs and are seeing some very weak results with Coombs phase testing. I know we need to revisit and reevaluate this testing, but there seem to be some problems with not testing through to Du too (unexpected positive results with Fetal Screens, changes in types between labs, using Rh neg blood when Rh pos blood would be OK, forgetting to do the Du testing on Rh neg babies of Rh neg moms, etc.)

I haven't been sure which way to go and whether the reagents can really and reliably make that differentiation with I.S. testing only. Can anyone help?

[Mabel Adams]

Of one thing you can be sure: the reactivity with various reagents at various phases will not reliably predict which patient will make anti-D.

Many monoclonal blend reagents have a different clone in them that reacts only at AHG and detects DVI well. The other clone or clones react with most of the other partial D antigens at IS. Those clones will also react at AHG. There are some published data on how these different reagents react--Transfusion I think had an article a year or two ago.

[Eagle Eye]

We do not send all these patient for molecular unless patient has multiple allos &/or warm auto---basically if molecular testing is going to change patient management...we spend extra $ for molecular testing.

[Malcolm Needs ☆]

We are using Immucor's reagents Anti-D Series 4 and Series 5. Can you really rely on these reagents to now detect Weak Ds I-V (quanitative weak D - I know this is old terminology, but it works) with immediate spin tests and to NOT detect Partial D VI (qualitative weak D)?? How do they work if you continue through to DU testing - still positive for I-V and negative for VI? Does anyone routinely test their "weak Ds" genetically now to determine real "partial Ds" that could make anti-D? If so, who does this testing in the US?

We are still testing through to AHG on D negs and are seeing some very weak results with Coombs phase testing. I know we need to revisit and reevaluate this testing, but there seem to be some problems with not testing through to Du too (unexpected positive results with Fetal Screens, changes in types between labs, using Rh neg blood when Rh pos blood would be OK, forgetting to do the Du testing on Rh neg babies of Rh neg moms, etc.)

I haven't been sure which way to go and whether the reagents can really and reliably make that differentiation with I.S. testing only. Can anyone help?

The attached diagram of the various Partial D RHD genes may help to show how different anti-D reagents can indeed react with some Partial D types and not with others. Essentially, the blue oblongs are RHD exons, the gold oblongs are RHCE exons, the blue and gold are RHD and RHCE hybrids and the small arrows are point mutations. From this, you can see that Partial DVI has the "least" RHD exons, and so, if this is translated to the resulting D polypeptide, it is quite "easy" to see how a monoclonal anti-D can be constructed to detect the other Partial D types, but not Partial DVI.

In most cases, the manufacturers state that the reagents should not be taken through to the IAT stage, as they are unreliable by this method.

I hope this helps a little bit.

[ATTACH]640[/ATTACH]

[Barbarakym]

We are still testing through to AHG on D negs and are seeing some very weak results with Coombs phase testing. I know we need to revisit and reevaluate this testing, but there seem to be some problems with not testing through to Du too (unexpected positive results with Fetal Screens, changes in types between labs, using Rh neg blood when Rh pos blood would be OK, forgetting to do the Du testing on Rh neg babies of Rh neg moms, etc.)

I haven't been sure which way to go and whether the reagents can really and reliably make that differentiation with I.S. testing only. Can anyone help?

First: AABB standards call to be sure you are not missing a potential fetal maternal bleed which can show up as weak D in the mom. From how I read the standard any weak D is suspect. Thus we only do moms at IS but baby of neg mom gets done to AHG (as required). Mom will get rhogam if baby is positive at coombs but otherwise baby is treated as the RH Neg they are by IS testing.

In my former institution (300 beds, level 4 neonatal unit)... in the 90's it was vogue to call Weak D positive as Rh Positive. We gave blood and platlets accordingly. During my time there I am AWARE of 6 people (may be more) who were Rh Neg by IS and Pos by Coombs that we gave an allo Anti D to by giving them Rh positive products. Due to risk we STOPPED the process in early 2000's. To me there is more risk in calling a negative person positive than the other way around.

Likewise, getting rhogam unnecessarily (genetically) is the lessor risk than sensitizing an Rh negative young mother to ALLO Anti-D. I believe from the wording of the AABB since 2005 (pamphlet by AABB on moms/babies) they believe so too.