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Eluates on babies with positive DATs


Mindy

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What is your facility's policy on performing eluate on a cord blood specimen that is DAT positve? Currently, our policy is to perform an eluate when the mother has 2 or more unexpected antibodies or when pos DAT can not be explained by ABO incompatibility and mom's ABSC is neg. I'm thinking there is no point in doing the eluate at all since any blood transfused to the baby will be antigen neg for mom's antibodies and coombs crossmatched with mom's sample.

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We will do an eluate if the cause of the positive DAT cannot be explained by either IAT testing on the cord plasma or phenotyping the cord cells. I have witnessed two cases where all the antibody was all on the cord cells and the cause of the positive DAT could only be solved when the antibody was eluted off.

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  • 7 years later...

We stopped doing LUI elutions last year as routine testing (thank goodness).  We still have the option to do them upon request.

 

If an IgG antibody was suspected of causing a positive DAT on a cord sample we would do an acid-elution.

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For those who routinely do eluates, what evidence/data have you to support such a policy?  Whether an eluate is positive or negative, when have eluate results changed the physician's decision to do or not to do?

I agree.  

 

Edited by R1R2
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  • 2 weeks later...

We do not routinely perform eluates on cord blood for that very reason.  It normally will not change the treatment of the baby.  If a physician wants an eluate they may request one.  We have only had 1 request since I took over last September and that was a miscommunication on a baby that was Rh Positive/ DAT negative and the RN misread the report and told the physician that the DAT was positive.  After I called and explained the results to the Doc he understood there was no need and cancelled the testing.

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  • 3 weeks later...

OK, from the land of generalist techs:  we do Eluates on babies ( which is maybe 4-6/ month) MAINLY because when we automated we felt it would be one more thing our techs wouldn't be able to do.  It basically keeps their eyes sharp and able to read step by step manual methods and the test itself is hard to mess up.  We still have occasions for Coombs crossmatches and them needing their microscope eyes tuned.

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we do not do eluate for the positive DAT on cord if it is due to ABO incompatibility and mother's antibody screen is negative.

We do an eluate if CORD DAT is positive and mother has positive screen.

We also do an eluate when CORD DAT is positive & there is no ABO incompatibility & mother has negative antibody screen and mother doesn't have history of antibody........We had a case like that almost 10 years ago where I was new tech and the DAT was very weak positive, I repeated it for my supervisor and my supervisor also repeated it before sending out to reference lab.........The ID was anti-Goa. Subsequently father was tested and father tested Goa+.

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  • 4 years later...

I am going to resurrect this topic from several years ago.  We only do cord workups for  O and/or Rh= moms.  We had an AB+ mom with an Anti-K and the discussion came up whether we should request the floor order a workup.  They did and the cord blood DAT was negative.  Had it been positive, our current policy would be to perform an elution.  We got to discussing WHY since we would predict what was on the baby cells and are pretty sure no treatment would change regardless of the eluate results.  Back in 2006, it looks like eluates on cord blood was about 50/50 from those who responded.  Just wanted to see if that still holds true or if more have done away with unnecessary elutions. 

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If they had ordered the workup, and the DAT was positive, would you have assumed that the reason was because of the anti-K?  Supposing the eluate had been negative with K+ red cells?  What would you have done?

Chances would be, in such a case, that the mother had made an antibody directed against a low prevalence antigen passed on by a paternal gene.  Next time it could be that this antibody is a lot stronger, and may cause HDFN (with the emphasis on HDF).  It may be that this "unknown antibody specificity" could be a "real nasty", causing severe HDF, but you wouldn't be able to advise the obstetricians to be on high alert during the pregnancy.

Admittedly, if the DAT had been positive, and anti-K had been eluted, this would have masked any antibody directed against a low prevalence antigen, but hey!

Edited by Malcolm Needs
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We only perform an eluate if +DAT can't be explained by an ABO incompatibility, known maternal antibody, or circulating RhIg. We will perform at physician request. but I don't recall that ever happening.  We only routinely perform cord blood testing on Rh negative moms & those w/ clinically significant antibodies.  Occasionally a pediatrician will request a cord DAT if a mom had a previously affected infant.

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No eluates, ever on neonates.  Won't change therapy in any way.  There are essentially no cases of autoimmune red cell disease in neonates, and the only source of IgG is mom.  If we didn't have a maternal specimen, or a history from the birthing facility I suppose we might do one, but there's really no clinical mileage in doing so.

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12 hours ago, Laurie Underwood said:

We will do an acid elution when the DAT is positive and the mother has a clinically significant alloantibody or the reason for positive DAT is not known. We do not perform an elution when it is due to ABO incompatibility.

How do you know that the positive DAT is due to ABO incompatibility, unless an elution is performed.  Surely, you are making an assumption (a very likely assumption, but an assumption nevertheless)?

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1 hour ago, EAB81 said:

We do the Lui Freeze eluate on all cord bloods with positive DATs. These mostly come back being a maternal-A1, B, or both when mom is an O and the baby is an A or B.

I think you may have meant maternal anti-A, rather than anti-A1.  Anti-A1 has NEVER been implicated in HDFN of any sort.

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Since we're on the topic of DATs performed on cord bloods, does anyone have a procedure I might look at for doing the DAT in gel? The previous BB Super had begun the task of researching but didn't get far. Thought maybe I'd pick up the torch.

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The NHSBT Reference Laboratories use a similar technique to an IAT.  The red cells are packed, and then diluted to the appropriate percentage, depending upon whether you are using BioRad (DiaMed) or Ortho (BioVue), and then just add the appropriate volume to the cassette and away you go.  It works a treat.

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21 hours ago, Malcolm Needs said:

The NHSBT Reference Laboratories use a similar technique to an IAT.  The red cells are packed, and then diluted to the appropriate percentage, depending upon whether you are using BioRad (DiaMed) or Ortho (BioVue), and then just add the appropriate volume to the cassette and away you go.  It works a treat.

Thank you, sir:)

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