"Rh-positive" vs. "Rh-positive, weak D" protocol

[johna]

Here is the scenario:

Pt. red cells reacted 1+ immediate spin with monoclonal anti-D by two different labs, no weak D test performed. Reported as "Rh-positive" by lab #1 and "Rh-negative" by lab #2.

What would be your reporting protocol for these results? Would you have proceeded to a weak D test when faced with these results?

As a side issue I have received information second hand that a blood bank supervisor at a local hospital claims that: "Recent data shows that MANY donors typing as weak D possess a partial D phenotype and are at risk for RhD alloimmunization.". The problem that I have with this statement is the "MANY". Obviously partial D exists but I hsave never seen any information stating that it's anything other than a rare occurence.

Comments, as always, are appreciated.

[Yanxia]

We will report it as Rh-negative and will not do weak D test for it .

[janet]

We would perform weak D testing (anything <2+ must be 'investigated').

If weak D reaction >2+ consider the patient weak Rh positive - give Rh pos units and not give RhIg unless Dr. insisted.

If weak D <2+ consider the patient Rh negative (I guess......better safe than sorry!!)

[galvania]

I think things are coming full circle. When I first started working in a lab (feels like a century ago, but not quite!), all our Ds were tested in precipitin tubes. We incubated for 1 hour then added 1 drop 30% albumin, then read after another 30 minutes. All negatives went on to have a Coombs. This was before monoclonals, of course. Anything that was negative or weak in the tubes but positive in the Coombs was called a Du and treated as a positive donor and a negastive patient. Then with the advent of the gel system, the anti-D was so much more sensitive that we could drop the Coombs. The stronger Dus gave strong results in the cards, the weaker ones weaker results. Anything 3 or over was called positive, anything less, a Du. Life was simple then!!At least, until you started finding D+ patients with anti-D in their serum!! Then came monoclonals and the realisation that there were 2 types of Du - partial Ds, who had a bit missing and could make an anti-D, and weak Ds who had everything, just less of it and therefore couldn't make an anti-D. How to distinguish? - Well, DVI being the most important partial D (among Whites, anyway!), everyone had to state whether their anti-D did or did not detect DVI. Test with 2 different anti-Ds, one DVI+ and one DVI-. Both pos - D+; Both -, D-; both weak - Weak D; one pos and one neg - then a partial D. Simple!! I hope your irony detectors are all working here! Because of course DVI is not the only partial D. In the States, I guess you get a fair number of DIVs and DVs without even knowing it. DIV reacts 4+ with most of the clones I know (I know 1 that gives a negative) and DV often reacts negative with most. Then to make things even worse, it's now known that some of the Weak Ds can make an anti-D too. So now we call everything a D variant. Like I said, we've gone full circle. Maybe microarray will provide the answer in the future. And they're not so very rare. I remember we once had a card out many many years ago with human anti-D and anti-CDE. We started getting lots of complaints because the D was positive and the CDE negative. It turned out that they were all RoHar and the anti-CDE wasn't detecting this variant. And when I say lots - it was at least 30 in the first couple of weeks. Obviously, we recalled the card. Shame really, it would have been interesting to see what the real frequency of RoHar was.

[bbbirder]

I would call it negative. no weak D.

(Remember, you will need to do a fetal cell stain to determine Post-partum RhIG dose, because the fetal screen will be positive in these women.)

I don't know if the "many" is accurate, but Partial D's and even some Weak Ds (and DELs) can definitely make anti-D. The "D variants" reactions with anti-D reagent can vary from weak to very strong in some partial Ds, depending on the reagent, but more so depending on the type of partial D. The only way to really tell Weak Ds from Partial Ds is to do molecular testing.

We try to follow what the AABB "Guidelines for Prenatal and Perinatal Immunohematology" says... "Only when prenatal tests for Rh are unequivocal and clearly reactive (>/= 2+) should the woman be considered Rh-positive." Interestingly, John Judd, who put this together, said on the AABB member forum that he uses </= 3+ when using Gel anti-D testing.

Linda Frederick

[AMcCord]

I have assumed that the AABB Guidelines were written with tube testing in mind. Does anyone know whether gel testing was a consideration when the quidelines were written? Just curious...

[Eagle Eye]

If Gel gives you 2+ or weaker reaction and your tube method IS=neg, weak D testing is 1+ or weaker.................Would you call this patient Rh positive or Rh negative. If patient OB ......give RhoGam or not??

[Yanxia]

I will call this patient Rh negative, if he/she is a donor, it is Rh positive. If patient OB will not give Rh0Gam according to some rule, but I think in this kind of case it is better to give prophylaxis. I don't think immunize by baby's cell is differ from transfused cells. Don't give prophylaxis in weak D maybe because the economization.

This just my view, opposed view is appreciated.

[galvania]

If Gel gives you 2+ or weaker reaction and your tube method IS=neg, weak D testing is 1+ or weaker.................Would you call this patient Rh positive or Rh negative. If patient OB ......give RhoGam or not??

I think this would be a very curious result. The gel technique is extremely sensitive and will pick up the majority of weak Ds (European box inserts state that anything less than a 3+ to be considered as a weak D) However, in my experience, testing of samples with a result of 1+ or 2+ with a weak D confirmation test (by IAT) is invariably stronger than the result in gel when I use our weak D confirmation reagent (exception - DIV is negative - but these give 4+ reactions with the ordinary Ds anyway).

It has turned unseasonably COLD here - -1° already. December weather!! Please send over some sunshine!!:cool:

[johna]

I think this would be a very curious result. The gel technique is extremely sensitive and will pick up the majority of weak Ds (European box inserts state that anything less than a 3+ to be considered as a weak D) However, in my experience, testing of samples with a result of 1+ or 2+ with a weak D confirmation test (by IAT) is invariably stronger than the result in gel when I use our weak D confirmation reagent (exception - DIV is negative - but these give 4+ reactions with the ordinary Ds anyway).

It has turned unseasonably COLD here - -1° already. December weather!! Please send over some sunshine!!:cool:

I would have to agree with you Galvania. Weak D reactions by IAT with rare exception turn out to be stronger than gel reactivity.

On a side note, those of us in the Southeastern U.S. suffering from drought conditions would be more than willing to exchange some sunshine for a few days of rain.

[geekay]

Here is the scenario:

Pt. red cells reacted 1+ immediate spin with monoclonal anti-D by two different labs, no weak D test performed. Reported as "Rh-positive" by lab #1 and "Rh-negative" by lab #2.

What would be your reporting protocol for these results? Would you have proceeded to a weak D test when faced with these results?

As a side issue I have received information second hand that a blood bank supervisor at a local hospital claims that: "Recent data shows that MANY donors typing as weak D possess a partial D phenotype and are at risk for RhD alloimmunization.". The problem that I have with this statement is the "MANY". Obviously partial D exists but I hsave never seen any information stating that it's anything other than a rare occurence.

Comments, as always, are appreciated.

Hi there !

I fully agree with that Blood bank supervisor who has said so...

I really wonder why people go for "escapism" and try to avoid the "Du test" (negative confirmation test) for the donors. But same applies for the Blood bank set up where we are supposed to give a firm report to the patient before or after transfusion. Why I said "supposed to" is , not all hoapitals in all places do give reports to the patients when they get blood transfusion in their centres.

After all it is a matter of 50 minutes, if at all, we do by meanual technique...right ?

Why dont all of us play it safe...safer and safest ? afterall, thats BLOOD BANKING is all about....right ?

best wishes to everybody...

[macarton]

We had a similar case. Turns out the patient was given Rh positive cells at another hospital a few weeks earlier.

[galvania]

But what exactly do you mean here by 'playing safe'? I would say that this is not the same thing for a patient as for a donor. 'Playing safe' for a donor means checking that your Dnegs are true Dnegs with the most sensitive test you have available (and that usually involves an indirect antiglobulin test with a very good anti D). On the other hand for a patient, playing safe means erring on the side of Dnegative in cases where there is doubt - in other words, if your routine test is Dneg, then treat as a Dneg. But, going back to donors, as donors often themselves become patients, then something similar to 'treat as a D+ donor and a D- patient' should be written on their donor card in the case where the routine test is negative but a more sensitive test is positive. If you have access to molecular biology then of course you can write exactly what the result is - but you still need to know whether to treat as pos or neg if it's a patient...

[ChrisH]

So you are saying is that if a patient is IS +- (weak) you would call that patient as rh positive.

But what exactly do you mean here by 'playing safe'? I would say that this is not the same thing for a patient as for a donor. 'Playing safe' for a donor means checking that your Dnegs are true Dnegs with the most sensitive test you have available (and that usually involves an indirect antiglobulin test with a very good anti D). On the other hand for a patient, playing safe means erring on the side of Dnegative in cases where there is doubt - in other words, if your routine test is Dneg, then treat as a Dneg. But, going back to donors, as donors often themselves become patients, then something similar to 'treat as a D+ donor and a D- patient' should be written on their donor card in the case where the routine test is negative but a more sensitive test is positive. If you have access to molecular biology then of course you can write exactly what the result is - but you still need to know whether to treat as pos or neg if it's a patient...

[Mabel Adams]

I think this is the part about patients rather than donors. She means a patient that reacts weakly would be considered D neg, I'd say.