Mabel Adams

We used to do weak D tests with post-partum RhIG workups because we did a full blood type and antibody screen with them to make sure mom was a candidate. (Also, to look for massive FMH that would cause an Rh neg mom to look like a weak D but that was before the Fetal Screen/rosette test was invented.) In those days, weak D pos moms were not RhIG candidates, but they are now. With modern reagents, those who react only at AHG anti-D testing are likely to be partial D VI and more likely to make an anti-D. We would rather not find them and just call them Rh negative from the IS test so we don't do weak D testing routinely on obstetric patients. We all dropped the antibody screen when we started using sensitive techniques like gel that picked up the 28 week RhIG dose at the time of delivery. If the screen was negative, you gave RhIG; if the screen was positive with anti-D (unless it was super strong) you still gave RhIG so why do the test if it won't change the treatment? Now we do weak D tests only if the Fetal Screen is "diffusely positive" to understand if a weak D is causing it. We get surprisingly few of them. Of course we do weak D tests on the babies of Rh neg moms.

There was an article in Transfusion a few years ago. I think the research came out of Pennsylvania. Sorry, can't find the reference at the moment. Mayo has a powerpoint called Emergent Use of Group A Thawed Plasma that I hope is still at this link. MayoMedicalLaboratories.com/hot-topics

Plus we should remember the goal of each test. In the case of prenatal Rh typing, identifying the patient who should get RhIG to prevent possibly making anti-D whenever possible is the goal, not generating a binary pos/neg answer. Unfortunately the reagents available aren't perfect for this but we need to be able to defend our decisions to the woman who makes anti-D and never has another healthy pregnancy.

We still use a BBID# because we have too many situations (pre-ops, outpatient transfusions) where patients aren't wearing Epic bands when their specimen is collected. I think we still have too many work-arounds too. We have not yet been live for a year. We have a flowsheet row that the nurses are expected to answer "Blood Bank band # checked and matches" but they aren't perfect at documenting it. I would be really careful in mapping what you are checking as you create these things because comparing BB band numbers from the unit in hand with what came across from your BBIS is not useful if you don't also check the BBID# on the patient. In fact, it could give a false sense of security. Someone could have used the wrong specimen in BB and put that ID number into the computer so all of the checks in the computers will match between the unit and the computers but the blood did not come from that patient and he has a different number on his wrist. Sorry if I am misunderstanding the process.

Do you perform a Fetal Screen (rosette) test on the Rh neg mother of a term infant who was stillborn (for whom you can't get a blood sample) or do you go straight to the Kleihauer-Betke test on the off chance that the baby could be a weak or partial D not adequately detected by the Fetal Screen kit?

I wonder if places that are starting to stock whole blood for MTPs end up needing to pack the units toward the end of their dating and thus have plasma they would like to sell also. Back in the days of whole blood in the 80s that was a normal thing but rules weren't so tight then either.

Same as AMcCord. To BankerGirl's point: I have tried to convince our neonatologists that they don't need to do routine cord workups on O pos moms but have made no traction. It is in their national guidelines as an option and they are more comfortable keeping it.

Also, do you have any references to help me make sure I understand the mosaic mechanism vs. chimera? If I follow you, chimeras would have a mixed red cell population from the embryo stage but a mosaic might have had a spontaneous mutation in a red cell precursor line at a later time. Is that right? Is this similar to how it works for people whose D antigens weaken with leukemia?

Are you referring to the Alba Partial D kit?

Has anyone ever seen a mixed field (both Ortho MTS gel and tube using Quotient/Alba Anti-D blend at IS) D type in someone not recently transfused? A recent prenatal sample showed this result but medium resolution molecular testing showed normal Rh genetics. Ultrasound reportedly was fine with one baby. The molecular lab says we should still consider the patient Rh negative because she is not Type 1, 2 or 3 Weak D but she has an unusual serologic type. We could order the high resolution testing for RHD-cDNA for another $750. I would like to hear of others' experience with something like this to better understand what the additional testing might tell us. Apparently it won't tell us if she is a chimera but would identify any mutations in the RHD gene. but would we then know if she could make anti-D?

I think the antibody screen done at 28 weeks is to make sure that the current pregnancy will not likely be affected by HDFN. A secondary effect is to know not to give RhIG if already clearly sensitized. The OB guidelines in the US don't require testing at 28 weeks; they can just give the RhIG. Based on those points, I would not see a need to have the injection time tied to the testing date. I guess I would want a screen after, say, 25 weeks if they are doing one at all if it is to serve to predict the likelihood of HDFN. We detected an anti-D in recent years on the 28 week sample of a first pregnancy and the baby was very affected by HDFN after born at 35 6/7 weeks.

Maybe you can identify 3 employees who meet the typing criteria willing to give you blood when you need it. Might be some regulatory hurdles to that nowadays though.

I think I recall this number is more like 60%, although maybe that was of those transfused, not pregnant.

What we do might depend on if I am here and see the reactions or if I am handling it by phone at 2 AM. I have had calls where what I heard them ask was not what I found when I got to work the next day.

We scan them into the chart and keep the original copy in blood bank for those still done on paper. Now we mostly use the documentation in the EMR as the "signed" record.