Partial D that comes and goes?

[rbayliff]

This past weekend, we had an OB patient that typed upon admission as A Negative. She delivered an A posititive infant. The mother's fetal screen post-delivery was positive, and the same result was obtained upon repeat. DAT (poly-specific and IgG) were both negative. The tech went on to perform a KB stain, which was negative. She then retyped the patient, using the original admission specimen, and the patient was showed a 2+ positive on the Du test. Our policy is to do the Du testing on all Rh negative samples. When the tech reviewed the patient's history, the patient was typed as A Neg in 2007, A Pos (Du Pos) in 2008 (both of those were by the previous bb supervisor), and A Neg again in 2010. In 2007 and 2010 the Du test was negative. Why is the Du sometimes positive, and other times negative?

We use the tube testing method for our types.

Edited March 2, 2011 by rbayliff

[David Saikin]

Are you using different types of anti-D over the course of the years? Some will not detect DVI others will. It is odd that the same specimen tested differently . . . sensitized cells worked with the original weak D? If the fetal screen is macro positive it is a good bet your pt is D+ (weak D) . . . that should be a clue before performing the KB.

[rbayliff]

I don't remember any changes in our anti-D reagents during that time. The tech that did the KB this weekend commented that she thought it odd that it was macro positive (which was a clue to me) but she didn't pick up on it. The tech that did the initial type is concerned since two people got different results on the same specimen. My concern is why does it sometimes show up and other times it doesn't.

[John Eggington]

Some have suggested that D ag density may 'vary' during pregnancy. This would explain a few things, but I'm yet to be convined (now someone will post data ti confirm this!). I'm more inclined to think that the reactions of 'weak D's' are more more senstive to small variations in test parameters; different batches of the same reagent, a minute more or less in incubation time, different operators, etc. Is this patient C or E positive? This might give a clue as to whether the patient is 'weak D' (not forgetting testing against a panel of anti-D's or molecular investigations).

[galvania]

I presume your Du test involves testing by indirect Coombs? Manual antiglobulin tests are not always that reliable and very difficult to standardise because there are so many variables

[dotahill]

We recently had this issue with 2 OB patients. Talk about frustrating. Both typed as Rh negative before pregnancy, and for their prenatal work-up, they were DU positive. These results led our lab to change our DU testing practices. We now only do DU's on cord bloods and babies. AABB supports that if a mother is testing DU positive, they should be treated as Rh negative and should receive Rhogam.

[ejsommers]

We only do Du testing on cord bloods and babies

[LisaM]

Here's another scenario that happened to me, just last night, that I'd like to toss out there for input:

A month ago, I got a prenatal sample on a patient, and at the time, I remember clearly, that the "D" in gel was weak--a 1+ reaction. I repeated it in tube, and again, it was 1+ in tube also, so I signed her out as Rh positive, as the reactions were clearly macroscopic.

Last night, I got another sample on this person, and it appeared that the D had weakened to the point that in gel, it was barely positive at all. I repeated her in tube again, and same thing--just barely positive macroscopically, but when viewed under the microscope, you could see many large clumps, so it was definitely positive.

Just for kicks, I ran it through as a Du test, and with IgG after incubation, the patient came up as 4+ positive on the D. I left it for supervisor review, today, and will see what comes of it tonight when I get in to work, but anyone have thoughts on that? Can your D-antigen weaken during pregnancy?

Unfortunately, I have no other information on this patient other than she's pregnant, because it's a sample that is shipped in from another facility for testing at ours.

[Malcolm Needs ☆]

Here's another scenario that happened to me, just last night, that I'd like to toss out there for input:

A month ago, I got a prenatal sample on a patient, and at the time, I remember clearly, that the "D" in gel was weak--a 1+ reaction. I repeated it in tube, and again, it was 1+ in tube also, so I signed her out as Rh positive, as the reactions were clearly macroscopic.

Last night, I got another sample on this person, and it appeared that the D had weakened to the point that in gel, it was barely positive at all. I repeated her in tube again, and same thing--just barely positive macroscopically, but when viewed under the microscope, you could see many large clumps, so it was definitely positive.

Just for kicks, I ran it through as a Du test, and with IgG after incubation, the patient came up as 4+ positive on the D. I left it for supervisor review, today, and will see what comes of it tonight when I get in to work, but anyone have thoughts on that? Can your D-antigen weaken during pregnancy?

Unfortunately, I have no other information on this patient other than she's pregnant, because it's a sample that is shipped in from another facility for testing at ours.

I have certainly heard of the D antigen apparently getting stronger during pregnancy, but I am not sure that I have ever heard of it getting weaker. I'm not saying that this has not been reported; it is just that I do not recall reading about it (but, then, I haven't read every paper that has ever been written - just most of them!!!!!!!!!!!!!!!!!!!!!).

THAT WAS AN ATTEMPT AT A JOKE.

[LisaM]

^^Maybe you should get pregnant, Malcolm, and we'll test your "D" before, during and after. LOL! (that was an attempt at a joke, too! haha)

But yeah, it was one of those "WTF??" moments and I'll certainly post in what the supervisor decided, after I get into work tonight. I don't think, though, that it was a mis-draw as in the wrong patient was drawn one of the times.

[Malcolm Needs ☆]

^^Maybe you should get pregnant, Malcolm, and we'll test your "D" before, during and after. LOL! (that was an attempt at a joke, too! haha)QUOTE]

The only pregnancy I've ever achieved is a pregant pause - Oh actually, that's not true of course (HUGE apologies to my wife and son!!!!!!!!). WHat I meant ot say is, I've never been pregnant.

I don't think I would be a good model in this case LisaM; I'm R1R1.

[LisaM]

^^LOL and don't look at me, either--I'm Rh-positive and my parts don't work anymore after chemo fried them, so those days are over for me!

[LisaM]

9pm--and the verdict is.. . . . *drum roll*: We're leaving the patient signed out as Rh positive. I guess it was enough with the supervisor to accept it as such with the very weak macroscopic reactions.

[galvania]

Dear Lisa

I would NOT be happy to call this patient Rh D positive. She is clearly some sort of D variant, probably a weak D - but I would definitely want to do some more work (ie molecular biology) on this one before treating her as a pos as she is an ante-natal case. If it were a man or an old woman like me, then OK, positive is fine.

As for the difference in reaction, when you have these really weak reactions tiny differences such as concentration of the cell suspension, temperature, age of the cards can all make a difference.

[LisaM]

Dear Lisa

I would NOT be happy to call this patient Rh D positive. She is clearly some sort of D variant, probably a weak D - but I would definitely want to do some more work (ie molecular biology) on this one before treating her as a pos as she is an ante-natal case. If it were a man or an old woman like me, then OK, positive is fine.

As for the difference in reaction, when you have these really weak reactions tiny differences such as concentration of the cell suspension, temperature, age of the cards can all make a difference.

Thanks, and my thoughts exactly. When I first ran this person a month ago, the reactions were very clearly macroscopic 1+, and I did put a comment to that effect on the electronic report, that they were weakly positive. Then when I got her again the other night, the reactions had decreased, and I thought "Oh crap!". I knew something funny was going on, and that testing beyond what we're capable of at my facility probably should be done, and that's why I didn't even result it, and left it for the supervisor.

She decided to leave her as the A-positive I'd originally gotten, and signed out my work herself, so at least that one's off my own hands. I think that the thought process was that this person isn't part of our patient base, and we don't have to worry about her, since we're only doing reference lab-like testing on these samples that come in. .. .I don't necessarily agree with all the practices and decisions that go on where I work, but I also have learned that there are times when I need to keep my mouth shut, and this was one of them.

[Joanne P. Scannell]

The FIRST thing you need to do is check out the capabilities of your Anti-D reagent(s)!

Some detect 'weak D' by I.S. while others need 37oC incubation, while others need AHG Phase.

Furthermore, some detect 'weak D' but not DVI (D Category VI) in the same.

Read your package inserts, that info is there.

DVI, if I am correctly informed, is the 'weak D' that will develop Anti-D. The others don't.

Anti-D with MTS (ABD Card, Anti-D Card) will not detect DVI, therefore correctly categorizing the patient as D neg. 'All' other 'weak D' are positive, therefore correctly classified as D-pos.

btw: I do believe the reason we stopped using the term 'Du variant' or 'Du Pos' was because, as we got to understand the D antigen better, these cells really are D-pos; they just bear either smaller amounts of D genetically or inhibited by C (and some claim E as well) in cis or trans position ... so different from what I was taught as a student!

Bottom line: Know the reagents you are using and be sure you are interpreting the results using the specific reagents limitations/capabilities.

And realize that reagents are different and that they have changed over the years ... even within the same manufacturer.

Edited June 16, 2011 by JPCroke

[LisaM]

^^Thanks JP! I'll read out anti-D package insert tonight when I get in to work. I believe it's Immucor brand that we use for that, and we normally only do Du testing on babies, but with the batch that comes from the other facility, they insist upon it, each time we get an Rh negative, and even each time the patient comes in for a repeat type and screen. A bit wasteful as far as reagent, in my opinion, because we primarily use gel for ABO testing, but have to switch to tube just for the Du's on these people.

Regardless, our procedure for Du's is to immediate spin them, then incubate at 37 degrees celsius for 15 min, then right into the cell washer with no spin after incubation, then add IgG. We don't (or aren't supposed to) use the microscope except on the babies to verify a negative reaction at IgG phase.

I was very confident the first time around with this patient in calling her Rh positive, but was more than a little surprised with the second sample and the decreased reactivity. I was thinking, too, that it might be good to antigen type her for E, C, e and c, just for kicks to see what her set up is. Maybe if I have some time on my hands tonight I'll do that.

[LisaM]

9pm--Update!

Ok, so I antigen typed the patient for C, c, E and e, and she turned up positive for all of them! I called the Red Cross reference lab to consult with them, explained the whole thing, and they said that it's uncommon, but entirely possible to have a phenotype like this. Also, they said to watch the patient, because those with this phenotype are at risk for developing an anti little "f".

So that's the update as it stands now!

[galvania]

Helo Lisa

Actually I would not have been happy to call her positive on the first results you got - not for a woman who is pregnant. 1+ in gel is weak for a weak D (if that makes sense) - and the fact that it didn't come up any stronger than this in Coombs would make me suspicious

[Malcolm Needs ☆]

I wouldn't be too worried about the lady making an anti-f (anti-ce), as this specificity has only ever been implicated in a mild form of HDN and mild, delayed transfusion reactions.

I would, however, thoroughly agree with Anna about the D group. It could even be that the lady has two different partial D types, one on each chromosome 1 (there I go looking for zebras again).

[LisaM]

Helo Lisa

Actually I would not have been happy to call her positive on the first results you got - not for a woman who is pregnant. 1+ in gel is weak for a weak D (if that makes sense) - and the fact that it didn't come up any stronger than this in Coombs would make me suspicious

Hello and thanks Anna and Malcolm!

I called her positive the first time around, because it's our policy to do so when we have a macroscopic reaction, and the computer system makes us choose one way or the other and won't let us sign it out as "Rh negative, Du positive". I did not run a Du the first time, as it was clearly positive, though weak, but did the second time and that came up as a 4+ with the IgG.

Our supervisor left it at the Rh positive, since we were seeing positive reactions macroscopically, however weak they were. Unfortunatley with these samples, they are shipped in from another facility, so we have no history on the patients, or any idea what happens to them other than just what we see and report when we type and screen them. I left my antigen typing from last night for the supervisor, to let her decide if she wants to recommend further testing for this patient through their own facility, or just leave things as is.

Regardless, I've pretty much done all I can with it, with the means I have at my disposal, and I at least feel confident that I gave as much information as I could and documented it as such.

[tricore]

I wouldn't be too worried about the lady making an anti-f (anti-ce), as this specificity has only ever been implicated in a mild form of HDN and mild, delayed transfusion reactions.

I would, however, thoroughly agree with Anna about the D group. It could even be that the lady has two different partial D types, one on each chromosome 1 (there I go looking for zebras again).

Malcom,

If you don't look for the zebras you won't find them. I like to look for zebras. It is what makes blood bank so interesting.

Michele

[Malcolm Needs ☆]

Actually, having thought about it, it is more likely to be an R2 (with a Weak D Type 2)/r', than a Partial D on both chromosome ones (D*cE/dCe).

[BB_LADY]

hello everyone,I am just new here & I'm glad to find this interesting site...I have a question & everybody's welcome to answer...This might be a stupid question but I am not an experienced blood banker like you guys.. here's the scenario my pt. is A Rh Pos pregnant lady,AB screen is positive my ABID panel A & B is clearly anti-D.Autocontrol is 3+ but my DAT is negative is this possible? pls. I need heeeelp,thanks

[Malcolm Needs ☆]

From timt-to-time you do see cases where the auto is positive, but the DAT is negative, which would suggest an auto-antibody.

Please could you give us a little more detail, such as the lady's ethnic origin?

Have you tried enzyme treating the panels and the auto? It may just be that the antibody is an "auto-anti-D-like" antibody. It may also be worthwhile testing the lady's plasma against group O, rr, cord blood.