Weak D testing

[AUDREY]

Hi,

AABB states that weak D testing must only be performed on neonates to determine Rhogam candidacy. That being said, how many facilities are still doing weak D's on all their patients? women of childbearing age?.We are having a problem picking up the weak anti-D reactions on immediate spin. Some of the weak D patients show weak 1+ reactions on immediate spin that become 2-3+ if carried through IgG.Is this a problem for anyone else?I worry that if the techs are missing these reactions, what are they missing on the IgG tube antibody screen and panel reactions. Suggestions are welcome.

[Malcolm Needs ☆]

There is very little evidence in the literature to suggest that babies who express the weaker partial D antigens are able to stimulate the maternal immune system to produce an alloanti-D. There is much more evidence to suggest that babies who express certain of the weak D antigens can stimulate the maternal immune system to produce an alloanti-D. I was involved in a case where a baby with weak D type 3 stimulated its mother to produce an alloanti-D. I would, therefore, advocate the testing of babies red cells for weak D antigens.

I cannot, however, see the point of testing all individuals for weak D, apart from the fact that such testing now and again throws up novel genotypes for the weak and partial D's, which adds to our font of knowledge concerning the human genome. If D typing is uncertain, give D Negative cellular components to females of any age of child-bearing potential (horrible phrase, but it is, nevertheless, that which is in vogue in the UK) and to individuals of either sex if they are, or are likely to become, transfusion dependent.

Otherwise, I would advocate giving D Positive cellular components to most males and to females who are beyond child-bearing potential.

This is not to say that this regimen is followed in all hospitals. We actually had a sample in from one of our customer hospitals on a 98-year-old male in not too long ago asking if he was a weak D, partial D or D Negative! WHY????????????

[Fluffy agglutinates]

Our current guidelines here in the UK do not advocate testing neonates for the D antigen by IAT. Part of the reasoning behind this is that the standard anti-D in use for all patients will detect most examples of weak D ( a pos is still pos right? No matter how weak?). Also this avoids the hospital lab carrying 2 different anti-D reagents in stock that potentially could be used on the wrong patients.

We purposefully avoid detecting partial D type VI in our patients, therefore type them as D neg & they get D neg products (unless Malcolm gets his hands on them & they happen to be a man! I know a certain retired man from Leeds who'd be very annoyed with you over that!).

Having said that it does make life a bit more boring as everyone is D+ or D- with rarely anything inbetween!

Also to answer your last bit - perhaps in their training the emphasis needs to be on the difference between reading a test performed using monoclonal standardised antisera & those testing patient antibody which will always be weaker? I was always taught that when looking for patient antibody the tubes must be treated much more gently & that even the weakest reaction could be significant for the patient. Failing that may be move over to column technology where the reactions are captured & cannot be tapped or rolled away!

Edited May 26, 2009 by Fluffy agglutinates

[ldlashley]

It is hard to break some old bloodbankers.

We are finally only testing for weak D in women of "child bearing potential" in our tri county area (women <50 yo). But regardless I am of the belief of giving even the weak D's Neg Products. Shoot Me!!

We are giving RH specific Plt Pherisis, and if the :cool:Physician does not want to wait for Neg units to arrive at our facility, we give 1 dose of RHIG per 3 units of Plt Pherisis.

[Malcolm Needs ☆]

Idlashley, I can only say "BANG"!

[PaulSunV]

The questions asked as I see them are as follows:

How many facilities are still doing weak D's on all their patients? Of the three hospitals I have worked at in the last 6 years all of them still require a weak D testing be performed on all patients. It is my understanding that the entire corporation of hospitals I am currently working for which includes 19+ different hospitals/medical centers/Clinics of varying sizes also do weak D testing on every patient. But because these facilities are interconnected electronically and as they are all required to perform history checks on all patients they are only required to perform the weak D testing if it has not been performed at least twice before at any one of the other locations.

How many facilities are still doing weak D's on women of childbearing age? See answer above.

Some of the weak D patients show weak 1+ reactions on immediate spin that become 2-3+ if carried through IgG.Is this a problem for anyone else? This is not a problem as the weak D testing is performed on all samples that appear to be negative at immediate spin. Secondarily if a reaction is less than 2+ the tech is required to perform a D control or a DAT on the patient sample.

Suggestions are welcome. The previous answers relating to tech training is the only way to obtained the desired result.

Now as to the reasoning behind the continuation of weak D testing I have none. There is always the answer that old blood bankers are hard to change as are conservative pathologists. I have on several occasions suggested as did my predecessor that weak D testing is only needed on a limited bases.

I am more curious as to the quality of the platelet pherisis that are being produced. I am very doubtful that with the current equipment used to collect pherisis plts that there is any need for a Rhig to be given as the red cell count is negligible.

[Malcolm Needs ☆]

Hi PaulSunV,

Since the introduction of monoclonal IgM anti-D reagents, our Guidelines in the UK state that negative tests should not be taken through to the antiglobulin phase (something that I applaud).

We do, however, use a panel of monoclonal IgG anti-D reagents designed to detect partial D types, if there is a reaction with one of the IgM anti-D reagents, but not the other, or if there is a gross difference in the strength of the reactions, but both are positive, but these are designed to be used by the antiglobulin technique. We would also use this panel if the hospital says they are getting weak positive results, but we get negative results with our routine reagents, in case they are using different clones to us.

What I would like to know is, since the introduction of monoclonal IgM anti-D reagents, approximately how many individuals have you detected in your hospitals that give positive results by the antiglobulin technique, having given negative results by the immediate spin technique? I am prepared to bet that it is not that many, and when you compare the cost of the saline for washing and the anti-human globulin reagent, I am further prepared to bet that it is more cost effective to give these patients RhD Negative blood than to do the test.

As you suggest yourself, you are against this kind of testing, perhaps a cost/benefit analysis would show your managers/Consultants that this should only be performed on females of child-bearing potential.

I sort of agree with you too about your comments concerning anti-D immunoglobulin prophylaxis and apheresed RhD Positive platelets, howver, with the caveat that, if the patient has already mounted a primary response to the RhD antigen, even minute amounts of RhD Positive red cells can stimulate a secondary response (see the very early work by Prof. Pat Mollison et al).

Edited June 2, 2009 by Malcolm Needs

[TeachBB]

Weak D's on all known OB patients, newborns (we only have a NICU....we don't deliver babies - mom usually not available), Bone Marrow/HPC transplant candidates and on pt's that do not have time to wait for Rh neg plt pheresis.

[bbville]

We do weak D testing only on newborns to determine RhIg candidacy. Our blood bank is busy enough and short staffed enough that we try not to do unnecessary testing and that is what weak D testing is in other cases.

[Malcolm Needs ☆]

I agree entirely with you vsummerville that the vast majority of weak D testing is totally unnecessary.

[John C. Staley]

Malcolm, PaulSunV is currently setting in the chair I recently vacated. I spent the better part of 12 years trying to get them to stop wD testing all patients and only test new borns for RhIG determination for the mothers. The clinical pathologist over corporate transfusion would have none of it for a variety of reasons, non of them clinical, regardless of the piles of documentation supporting the change I provided for her.

I have heard through the grapevine that she is reconsidering. That would mean that the devil just bought a snow shovel!

[Malcolm Needs ☆]

Superb phraseology John!

[jhaig]

We dropped all weak-D testing last year. We do not deliver babies here so there's no need to worry about testing neonates. No need to determine a weak-D status for any other testing that we perform here. If a transfusion recipient types as Rh-neg, they'll receive Rh-neg blood prducts anyway, so why confuse the patient by telling them they're really Rh pos? The only way they would know better is if they were a regular blood donor and were told they were weak-D pos by the donor center.

[Malcolm Needs ☆]

I agree jhaig.

We've had dreadful problems with patients who were typed as D Negative way back before the introduction of monoclonal anti-D reagents, have gone back into hospital many years later, and have now been told that they are D Positive. With all due respect to the average patient, it is an almost impossible concept for them to understand.

The other times we have problems in the UK is when we have an individual who is partial D VI. Over here we treat them as D Positive if they are donating blood, but D Negative if they are receiving blood. Explaining that one to them is jolly good fun!

[jhaig]

Our issue all started when a female patient came to us for a prenatal type and screen. Up until this point we had done weak-D testing on all females of child-bearing age and we typed her as a weak-D positive. Well, of course, her hospital in Virginia said she was Rh-negative. Confusion ensued, and I decided that this was a headache I didn't want to have to deal with again:cool:

[Malcolm Needs ☆]

Don't blame you in the least.

[clmergen]

That is when you answer the question "Am I Rh neg or Rh Pos?" with a yes.

[Malcolm Needs ☆]

Love it!

[galvania]

And how do you treat the patient who comes up positive with the weak D test who was negative in the normal test? Does she receive Dneg blood or D+? Does she receive anti-D prophylaxis? If the answer to thatese two questions is 'no', then what have you gained by doing the test?

[Malcolm Needs ☆]

Quite right Anna.

By the way, please give my regards to Imelda when you see her next.

[aoliveg]

Hi Malcom

I can understood that we use a panel with monoclonal IgM anti-D reagent, for patient and childbearing women?, and a special panel with monoclonal IgG anti-D aditional reagent for newborn? So, what hapen with donors?, analize them like newborn... or there are another alternative???

[Malcolm Needs ☆]

Hi Malcom

I can understood that we use a panel with monoclonal IgM anti-D reagent, for patient and childbearing women?, and a special panel with monoclonal IgG anti-D aditional reagent for newborn? So, what hapen with donors?, analize them like newborn... or there are another alternative???

In the UK, the donors are tested with two anti-D reagents. One of these is called Totem (I can't remember who makes it, but will post tomorrow when I go back to work). This reagent not only detects partial DVI, but many, many other partial Ds (it is the best donor reagent anti-D I have ever used, but completely useless for patients).

I'm not sure what other countries use.

:):)

[TimOz]

Hi Malcolm,

Diagast (France) makes Totem. It is a good reagent and used 4 monoclones but is high protein and need a parallel Rh control.

[aoliveg]

ok, thanks to both,

So, it is clear that use of aditional anti-D blended reagent is very usefull for donors. Is the same for new born?

In my country, Chile, we do not have acces to Diagast reagent, but we have other options of anti-D blended reagent.

We will elaborating the recomendations for RhD typing and report, any help was very appreciated.

[Malcolm Needs ☆]

ok, thanks to both,

So, it is clear that use of aditional anti-D blended reagent is very usefull for donors. Is the same for new born?

In my country, Chile, we do not have acces to Diagast reagent, but we have other options of anti-D blended reagent.

We will elaborating the recomendations for RhD typing and report, any help was very appreciated.

Others may disagree, and I have published a poster concerning a Weak D Type 3 foetus causing the stimulation of alloanti-D in a mum, but I wouldn't get too worried about this; it is extremely rare for a weak or partial D foetus to stimulate alloanti-D in a mum.

If you are worried though, a blended anti-D reagent would work fine.

Somewhere in the dark recesses of my mind, I seem to think that Dame Professor Marcela Contreras, who was in charge of Diagnostics, Development and Research in the UK for many years, and is herself Chilean by birth, is now working in Chile. She would be able to give you much more authorative advice than me, if you can contact her.

You may be able to get hold of her via your own National Blood Service.

:):)

Edited January 13, 2010 by Malcolm Needs