Weak D problems...still??

[ElinF]

sorry, more questions on this issue!

So we have been using Gel for 4 years now and thought we had our weak D problems figured out. OB calls the other day and says they had a patient that was historical Rh negative. We reported RH positive. Repeat testing showed in tube she was weak D positive and the Rh was 3+ in gel so we called her rh Positive. Explained this to the nurse and she understood. In reading other threads on this issue everyone says to just drop the weak D testing. Well, we really don't do "weak D testing" - we do Gel.

So my question is do we just go back to doing Tube ABORHs on all prenatals instead of gel (and just report the D at IS). This is what we do on crossmatch patients. The weak D patients are usually so strong in gel we don't even know they are "weak D" because of the strength of the reaction?

The staff will love this change because I have talked endlessly how ABOs in gel will be the solution to our problems!.

[Malcolm Needs ☆]

I wouldn't compromise specificity for sensitivity in this case.

The patients ARE Weak D.

Let me put it this way, If you had a patient who was K+, k+, Kp(a+b+), and the k antigen was weak because of the KPA gene in the trans position, would you give them K+, k- blood? I think not.

[YorkshireExile]

We have the same "problems" as ElinF. We use gel and don`t do weak D testing on our prenatal patients, but if my gel reaction shows 1-3+ positivity I`m obliged to report it as RhD positive. I then put a result comment in stating that the patient is actually a weak RhD positive. If there is a discrepancy with the historical group being Rh Negative, I then have to explain that as well. Unfortunately with my wonderful(!) Cerner Millenium computer system I cannot actually report the group initially as Weak D positive, so I have to put the comment. If these patients required blood I would try to give them Rh Negative blood to be on the safe side.

[dgibaud]

Since we've started gel testing we use the gel result exclusively to report the Rh status. As others have experienced, we get the occasional patient who was either Du (back in the olden days) or negative by tube testing, who now tests weakly positive in gel. We routinely call these patients Rh positive, give them Rh positive blood, and withhold rhogam. We haven't seen any problems, but our sample size is quite small. Is there a problem with our practice?

Don

[David Saikin]

i would NOT have 2 different routine methods of ABORh typing. I use tubes for ABORh only for emergency release. . . a few times I have had tube IS Rhs that were negative and the routine gel type was 1+. You need to have a policy/procedure on how you are interpreting your gel Rhs. If you want to call anything less than 4+ a weak D go for it. If you routinely type some pts in gel and some in tubes you are asking for inconsistency. I would not go back to Weak D typing in tubes, but, it is your operation.

[ElinF]

i would NOT have 2 different routine methods of ABORh typing. I use tubes for ABORh only for emergency release. . . a few times I have had tube IS Rhs that were negative and the routine gel type was 1+. You need to have a policy/procedure on how you are interpreting your gel Rhs. If you want to call anything less than 4+ a weak D go for it. If you routinely type some pts in gel and some in tubes you are asking for inconsistency. I would not go back to Weak D typing in tubes, but, it is your operation.

My techs do not like doing gel ABORH for crossmatches because it takes to long if they don't have history. So we have kept with tube for those patients- and luckily not run into any problems...yet. but good point. And the reason we went to gel for prenatals was to hopefully curtail some of this mess.

Right now our policy on the weaker D reactions in gel is to perform a weak D to confirm (as our weak D testing in gel is in the process of being validated- mainly because we don't see that many weak D patients. I have about 10 1-2+ reactions so far in 4 years...). But if they are 1 or 2+ in gel, and it is so sensitive, I am so scared that one of these weaker patients is going to form anti-D.

I think we should just tube all our ABOs (as we are not automatued yet) and just to IS on all the Rhs. But that probably won't happen.

I don't know.

[Malcolm Needs ☆]

My techs do not like doing gel ABORH for crossmatches because it takes to long if they don't have history. So we have kept with tube for those patients- and luckily not run into any problems...yet. but good point. And the reason we went to gel for prenatals was to hopefully curtail some of this mess.

Right now our policy on the weaker D reactions in gel is to perform a weak D to confirm (as our weak D testing in gel is in the process of being validated- mainly because we don't see that many weak D patients. I have about 10 1-2+ reactions so far in 4 years...). But if they are 1 or 2+ in gel, and it is so sensitive, I am so scared that one of these weaker patients is going to form anti-D.

I think we should just tube all our ABOs (as we are not automatued yet) and just to IS on all the Rhs. But that probably won't happen.

I don't know.

Are your really weak reactions with patients that have the DcE haplotype, rather than the DCe haplotype? If so, they are probably Weak D Type 2, but they are almost certainly still a Weak D, rather than A Partial D.

[ElinF]

Are your really weak reactions with patients that have the DcE haplotype, rather than the DCe haplotype? If so, they are probably Weak D Type 2, but they are almost certainly still a Weak D, rather than A Partial D.

We do not do RH phenotyping on our Weak D patients, so I wouldn't know.

[Malcolm Needs ☆]

Why not? That sometimes helps - it really does.

[ElinF]

That is a good thought. We do RH phenotyping when we have an RH antibody, and we get so few of these Weak D patients that it wouldn't be that big of a deal. I will bring that up.

So if they are Weak D Type 2 are they treated any different than partial D? Partial D patients have a higher chance of forming anti-D right? Would we suggest Rhogam for patients that are the DcE haplotype? I need to educate myself on the details of weak D.

[Malcolm Needs ☆]

No, Weak D Type 2 (the usually Weak D found with the DcE haplotype) is not a Partial D, but sometimes is so weak it mimics one serologically. They don't need Rhogam, but it doesn't hurt if they are given it by mistake - it just won't do anything, as it will adsorb onto the mother's red cells.