Our facility is evaluating making a change to our process for Weak D testing for patients with a positive DAT. For years, if we were required to do a Weak D, but the patient had a positive DAT, we used to cancel the Weak D as invalid. Another hospital in our system mentioned that they tended to perform the Weak D, but then only cancel as invalid if the Weak D is positive. We are thinking about changing to this process, as we now have to result many babies as "Rh Unknown" and give their mothers Rhogam.
Per our Anti-D's package insert: "Red blood cells coated with alloantibodies or autoantibodies of the same or similar specificity as the reagent (i.e. cells that are DAT positive) may give weak reactions. This is due to decreased availability of antigen sites because of antigen blocking or steric hinderance. In extreme cases false-negative results may occur."
I'm worried about the "extreme cases" where a false negative could occur, but I cannot see this being common. Also, would you think that if the cells were coated with that much antibody, that we would see any other odd reactivity in the ABO/Rh? What do other facilities do?
Thank you in advance,
I am sorry if this has been discussed previous... I searched and didn't find anything. Quick question...
We are transfusion service that performs DAT's using poly-clonal IgG... if it is positive, we run the mono-clonal IgG, however, we do not run the C3d. How many of you would and/or do run the complement control cells for DAT QC in addition to Check Cells?
I have a question, but firstly good old story time for some context. I came across a patient who had positive antibody screen on all three screening cells used (BioRad). I was concerned this may be an auto and pan-reactive, and required units. Performed a monospecific DAT, showing a positive reaction to IgG only. By this time antibody panel finished cooking and showed the patient may have anti-Fya , but couldn't do phenotype. By this time I was nearing my shift so handed it over to my colleague and asked for some units to be crossmatched. However, he refused as DAT was positive and said he rather send the sample to reference laboratory for them to crossmatch. The next day I crossmatched units to verify if it could have been done in our laboratory (just because I am sad that way), and turn out the unit I crossmatched was compatible (which I wasn't surprised about)
Why does positive DAT (or the cause of positive DAT) sometimes interfere with IAT techniques (such as antibody panel and crossmatch) and sometimes it does not? If both use AHG, then wouldn't positive DAT with IgG cause antibody panels shows pan-reactive with red cells? But obviously it doesn't, but I'm trying to figure out why, and I'm sure the answer is quite obvious.
My laboratory seems very hesitant whenever they see anything regarding autoantibodies or positive DAT, and thinks that sample cannot be crossmatched in-house and needs to be sent off without even trying to investigate. Hopefully, by me asking this question, I can explain it back to my colleagues (but obviously take all the credit).
Cheers in advance,
Its been a while since I came back to this forum, but glad I feel like I have gained a lot more insight. I feel like I'm a bottomless cup.
So I come with a question, for which there is not going to be a definitive answer (but with BB, is there ever one?), but hopefully, I would gain a bit of understanding.
Background: So, our laboratory has started sending samples to reference laboratory for genotyping of the foetus by FDNA, which is great, since we would figure out the Rh(D) status of the baby (on most occasions) before they are born! So our laboratory has set up a flow chart which basically mentions that you do not need to send cord sample of Rh(D) negative mother if the baby is shown to be Rh(D) positive (or D positive, I am quite wary when trying to talk about Rh group), and only send cord if baby of Rh(D) negative mother if the FDNA shows the baby is Rh(D) negative, just to confirm the accuracy of FDNA. It sounds kinda counterintuitive, but we will soon be just not processing any cord sample for the ones we performed FDNA on. That means no cord Blood Group or DAT on a lot of post-delivery patients.
Question: By missing out DAT, we would possibly be missing out on detecting ABO incompatible HDN. How significant do you think it is in the early stages? Is it OK to wait to see if the patient shows signs of jaundice and for them to send a DCT sample afterwards?
Bonus Question: What does your Hospital/Laboratory do in the event of positive DAT on cord sample, and why do you do it?
I had a read through one of the articles stating about the significant of DAT, but they called the Rh blood group as Rhesus, so I'm not going to take them too seriously