We do weak D testing only on neonates 4 months old or less. All our D negative prenatals are given RHIG @ 28 weeks and if applicable after delivery. We have had 3 cases of weak D positive patients not getting RHIG and developing Anti D. We currently have a prenatal that another hospital typed as A Negative Weak D positive. She now has an Anti D. We sent her out for molecular testing and she is a partial D category 6 capable of producing Anti D which can cause fetal fatalities. This is the 3rd patient in 6 years we have had like this. That is why we do not do weak D testing on prenatal patients. The results of not getting Rhig can be devistating!

kmh76,

I have always practiced performing weak D testing especially on Rh-neg L&D patients at various facilities. The testing and interpretation is really not at fault here with you situation, it is the course of action or lack of action on part of the practitioners involved with making the decission to give RhIG or not. I suspect that they are not understanding that a patient with an altered D Ag (weak D, for the most part) can develope an allo-D (against an unaltered D Ag). I am sorry to hear of your situation and you are absolutely right about the devistating effect.:raincloud Are there any policy changes on the horizon?

kmh76,

I am writing to make a correction to my previous post. My initial understanding was that weak D testing would involve making a decision to give RHIG however I have realized that the positive weak D test would involve not giving RHIG. The real limitation of weak D testing is that it is unable to resolve the origin of the weak D; ie reduced expression of the D antigen (which would not produce an allo D, or if it did we would call it an auto D) or expression of an altered D antigen (ie D mosiac which could result in production of an allo D). As a result I think that I would agree with your view of not performing the weak D testing on L&D patients as there is little known negative effect of recieving RHIG when not truely necessary. I would also agree that if we wanted to be precise then a genetic work-up should be performed. I hope this helps in some way as I know it has helped me.