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"Du"


Antrita

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We only test for a "Du" (weak D) on Rh negative babies of Rh negative moms. This is so we don't miss giving a needed Rhogam. We use to do any females of child bearing age or younger. We had a 13 year old come in yesterday with a Type and Screen order. She had a history of being B positive. This was done when she was born. The CLS yesterday got a B negative blood type. Since her history was B positive he did a Du. The Du was positive. I did here phenotype and she was r'r ( positive for C,c,e and negative E). Since almost all Rh negatives are rr( positive c,e and negative C,E) could the positve Du be a carry-over of the C being positive? Wouldn't it be safer to give her Rhogam?

Antrita:confused:

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No, I don't think that "the positive Du is a carry-over from the C being positive." (Unless you are talking about what I say in the next paragraph but are using different terminology.)

This patient could be Ro r' (cDe/Cde) , for example, in which case the C gene in the trans position to D has sometimes been known to suppress the normal expression of the D gene, causing the individual to type as "Du." In this case, Rhogam would not usually be indicated. However, if the woman's red cells type as "Du" because she is genetically lacking some part(s) of the D antigen mosiac, considering her as a candidate for Rhogam would be the safe/prudent decision.

(I'm sure someone else could explain this more eloquently than I have...........You picked a fine time to go on Holiday, Malcolm!!!)

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I guess what bothers me is I've only had 2 "Du" positive patients since we quit doing them on anyone other than Rh negative babies with Rh negative moms and each time they either were E or C positive. So, I guess I can't make a case out of 2 patients but it does bother me. Also, having a pregnant 13 year old doesn't help.

Antrita

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Well, if she is Weak D positive, then her phenotype might more likely be R0R1 (vs. Ror' which would be rarer), with the Trans C/D causing the supressed D. As far as Rhogam? Many places do not do Weak D Testing and Rhogam won't hurt; so better to be on the conservative side, just in case.

Brenda Hutson, CLS(ASCP)SBB

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We do our blood typing in tubes and antibody screens in gel. We only do Du testing on Rh negative babies of Rh negative moms to make sure we don't miss a Rhogam. So if the patient had not been born here we would not have done a Du this time. We would have typed her as Rh negative and stopped there. There was one other time when we got an autologous unit from our blood supplier that was O postive. When we typed the patient we got O negative. We did a Du on her and it was positive. This was quite a long time ago and the whole Du thing had not started to bug me. This may seem like a really stupid question but why is there no little d?

Antrita

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We do our blood typing in tubes and antibody screens in gel. We only do Du testing on Rh negative babies of Rh negative moms to make sure we don't miss a Rhogam. So if the patient had not been born here we would not have done a Du this time. We would have typed her as Rh negative and stopped there. There was one other time when we got an autologous unit from our blood supplier that was O postive. When we typed the patient we got O negative. We did a Du on her and it was positive. This was quite a long time ago and the whole Du thing had not started to bug me. This may seem like a really stupid question but why is there no little d?

Antrita

Right, I understand that under normal circumstances, you would not have performed Weak D typing. However, there are instances where we go against that (and you mentioned some):

1. Discrepant Rh Typing from historical

2. Autologous unit labeled Rh Positive but patient types as Rh Negative Immediate Spin

3. You get a macroscopically positive Fetal Screen

And even for Institutions that do choose to perform Weak D typing on mothers, some will give them Rhogam and some won't. So again, it doesn't hurt to take the conservative approach.

As far as why there isn't a "d?" Is it because there isn't one, or is it because they have not identified one yet. You will have to ask God that one....but that is a separate issue from the Weak D.

Brenda Hutson, CLS(ASCP)SBB

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One of the reasons that she typed as weak D in the Du test is that she may be a partial D. Why risk not giving the RhIG. Partial D women should receive RhIG, they can make anti-D.

I agree. I believe some places are basing it on statistics in their decision to not give it to Weak D women; that even if they are Weak D, from a statistical standpoint, most won't make Anti-D. At least that has been the reasoning of 1 place I formerly worked. I am more familiar with the initial Post of stopping at immediate spin, so calling them Rh Neg and giving Rhogam.

Anyway, again, no harm giving the Rhogam so I am all for being conservative.

Brenda Hutson, CLS(ASCP)SBB

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Sometimes the Weak D is the result of missing part of the mosaic ag . . . sometimes RH2 © will not suppress D but inhibit antibody access to the D ag (steric hindrance) . . . whatever the cause, if your policy is not to do Weak D testing (even though you did it to evaluate the type discrepancy), I think you should give the RhIg. Do you (did you) give Weak D+ patients Rh+ or Rh= red cells? If you gave them Rh= cells, there should be no question about giving RhIg.

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Sometimes the Weak D is the result of missing part of the mosaic ag . . . sometimes RH2 © will not suppress D but inhibit antibody access to the D ag (steric hindrance) . . . whatever the cause, if your policy is not to do Weak D testing (even though you did it to evaluate the type discrepancy), I think you should give the RhIg. Do you (did you) give Weak D+ patients Rh+ or Rh= red cells? If you gave them Rh= cells, there should be no question about giving RhIg.

You are correct that the the "principle" is the same in your example. Again, whatever all considerations we come up with to exlain the results, the bottom line is:

1. Rhogam won't hurt

2. When in doubt, err on the conservative side, especially in the field of Blood Banking

Brenda Hutson, CLS(ASCP)SBB

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Hi Antrita,

I'll take a stab at your little d question. It's my first post, so don't rip me too hard.

Rh-negative folks still have an Rh protein (unless they're the Rh-null phenotype), it's just that their RhD allele is not immunogenic. An antigen is something immunogenic, that your body can make an antibody to. Just because your immune system doesn't make an antibody to the protein doesn't mean there's nothing there, and just because someone is Rh-negative doesn't mean they lack the protein that the antigen is a part of. I don't know if that makes any sense. Basically, Rh-positive folks have a form of the protein that is the Rh "substance" that people can form antibodies to. Rh-negative folks have the protein, too, but theirs is a little different due to mutation and the immune system doesn't recognize it as foreign and form the anti-D antibody to it. It's still a functional "Rh protein", it just won't form antibodies.

I think a lot of times people forget that the primary role of red cell antigens isn't to be an immune system target, their parent proteins (or carbohydrates, or whatever) do have roles. The Rh protein is a structural protein, the Kidd protein is a urea transporter, Duffy is a chemokine receptor, etc.

Take it easy,

Jason

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The patient in question is getting Rhogam. With the ok of my pathologist I am changing blood type to Rh negative with a long explaination in her history. We don't want her to miss any further Rhogam and I don't want to drive another CLS crazy.

What would you do, change her type or leave her a Rh positive?

Antrita

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Hello Antrita

The answer to your question - to give or not to give RhoGam - is one that is going to change over time as our knowledge about the D antigen becomes more and more complete. It is quite possible for a patient/donor to have a historical result that was negative and a new result that is positive. Techniques change, some are more sensitive than others and some clones will pick up some variants where others won't. However, when you have something other than a straightforward D negative or D positive, it is either because you have a weak D or a partial D. A partial D has a part of the D antigen that is 'missing' and can make antibodies to the missing part. A weak D can therefore always make an anti-D (to the missing parts of the D antigen) if exposed to a normal D antigen and therefore should always be given Rhogam when pregnant. The situation with weak D is more complicated. Firstly there are 2 reasons for weak D - the first is a change at the molecular level which results in less antigen sites per red cell. The overall majority of these can be treated as normal Rh. D positive BUT recently there have been some (fairly uncommon) types of weak D that have been found to make allo-anti-D antibodies. There is another type of weak D which is caused by the presence of a C in trans. That means the presence of a r' opposite something that contains D. In your case, if the patient was (I think I remember correctly) Ccee, then she would have to be Dce/Cde or Ror' (It couldn't be R1 on the other side, as the presence of a normal D would mask the weak D on the other allele). In this type of case you can give D+ blood - and no Rhogam, no problem.

The biggest problem is - how do you know what is the reason for your weak D. Not easy. However, if you have tested with several different clones of anti-D and you have some giving positive results and some negative, then you almost certainly have a partial D. If they're all positive, then only molecular biology will give you the answer......

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No, I don't think that "the positive Du is a carry-over from the C being positive." (Unless you are talking about what I say in the next paragraph but are using different terminology.)

This patient could be Ro r' (cDe/Cde) , for example, in which case the C gene in the trans position to D has sometimes been known to suppress the normal expression of the D gene, causing the individual to type as "Du." In this case, Rhogam would not usually be indicated. However, if the woman's red cells type as "Du" because she is genetically lacking some part(s) of the D antigen mosiac, considering her as a candidate for Rhogam would be the safe/prudent decision.

(I'm sure someone else could explain this more eloquently than I have...........You picked a fine time to go on Holiday, Malcolm!!!)

Sorry L106!

Antrita, if you go into References at the top of the page, click on Document Library, then click on User Submitted, then click on Educational Material, then click on "The Rh and LW Blood Group Systems" and download the PowerPoint lecture, you will find an explanation of sorts in slides 31 and 32, with a written explanation underneath the slide itself (if you don't actually open the show, but just scroll down the lecture). I hope that this is of some help.

You will see, in the lecture as a whole, that I say that individuals with the Weak D phenotype will never make alloanti-D. This is a bit of a "white lie" to make the situation more easily understood; actually, rare individuals with the Weak D phenotype actually have made alloanti-D.

:)

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You are correct that the the "principle" is the same in your example. Again, whatever all considerations we come up with to exlain the results, the bottom line is:

1. Rhogam won't hurt

2. When in doubt, err on the conservative side, especially in the field of Blood Banking

Brenda Hutson, CLS(ASCP)SBB

I agree entirely that Rhogam will not hurt in most cases, but beware of the lady with an anti-IgA or those that go into anaphylactic shock. This has nothing to do with the anti-D immunoglobulin itself; such people will react to all preparations that include human immunoglobulins.

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I not aware of any instances of a weak D typing being a "carryover" from C.

We would consider this patient a candidate for Rh Immune Globulin.

r'r is an unusual phenotype, but not really all that rare.

I think that the "carryover" stems from the days when human derived anti-D was used routinely for grouping. The most common contaminant in such antisera was a weakly reacting anti-C (usually an anti-Ce, as are most "anti-C" reagents - even the monoclonal "anti-C" reagents we use today), because the R1 (DCe) haplotype causing the immunisation of the anti-D in the first place is much more common than the R2 (DcE), Ro (Dce) (in the White population) and Rz (DCE) haplotypes that could cause this immunisation. This was the reason that an r'r (dCe/dce) red cell was always used as a negative control when using a human-derived anti-D reagent.

:)

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Sorry L106!

Antrita, if you go into References at the top of the page, click on Document Library, then click on User Submitted, then click on Educational Material, then click on "The Rh and LW Blood Group Systems" and download the PowerPoint lecture, you will find an explanation of sorts in slides 31 and 32, with a written explanation underneath the slide itself (if you don't actually open the show, but just scroll down the lecture). I hope that this is of some help.

You will see, in the lecture as a whole, that I say that individuals with the Weak D phenotype will never make alloanti-D. This is a bit of a "white lie" to make the situation more easily understood; actually, rare individuals with the Weak D phenotype actually have made alloanti-D.

:)

Yes, we once had such an individual. Upon sending some of the specimen to Dr. Garratty's Lab, they were able to determine by molecular testing that the patient was in fact a partial D (and yes, he had made an Anti-D).

Brenda

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Yes, we once had such an individual. Upon sending some of the specimen to Dr. Garratty's Lab, they were able to determine by molecular testing that the patient was in fact a partial D (and yes, he had made an Anti-D).

Brenda

Ah, yes Brenda, but I am not talking about individuals with a partial D (they are very obviously well-known to have the potential to produce alloanti-D); what I am talking about are very rare individuals that have been determined to be Weak D Type 1 and Weak D Type 2 by molecular methods, but that have, nevertheless produced a weak alloanti-D. Received knowledge suggests that such individuals just should not be able to do this (a bit like the fact that bumblebees should not be able to fly, but nobody has told the bumblebees this)!!

It is a b****y nuisance actually, because you have to tell the white lie to certain (junior) audiences (that Weak D individuals cannot produce alloanti-D) and tell the truth to certain other (more senior) audiences. The trick is knowing to which audience you are talking - and I seem to get it wrong more often than not!!!!!!!

:redface::redface::redface::redface::redface:

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Ah, yes Brenda, but I am not talking about individuals with a partial D (they are very obviously well-known to have the potential to produce alloanti-D); what I am talking about are very rare individuals that have been determined to be Weak D Type 1 and Weak D Type 2 by molecular methods, but that have, nevertheless produced a weak alloanti-D. Received knowledge suggests that such individuals just should not be able to do this (a bit like the fact that bumblebees should not be able to fly, but nobody has told the bumblebees this)!!

It is a b****y nuisance actually, because you have to tell the white lie to certain (junior) audiences (that Weak D individuals cannot produce alloanti-D) and tell the truth to certain other (more senior) audiences. The trick is knowing to which audience you are talking - and I seem to get it wrong more often than not!!!!!!!

:redface::redface::redface::redface::redface:

Hmmm...I wonder which audience I am part of...Ha Ha..I certainly "feel" like part of the junior audience at times.

Brenda Hutson, CLS(ASCP)SBB

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