Newborn Positive DAT

[Gkloc]

We had a mother who had a C - Section yesterday and a Cord Blood Workup was performed on it. The Mom is Type O Rh Positive (negative antibody screen) and the newborn typed as O Rh Positive as well but had a positive DAT. We are unsure as why this occurred. The testing was repeated on a heel stick and the same results were achieved. Any help anyone could give as why this could happen would be greatly appreciated. Thanks

[Bet'naSBB]

??  Maybe mom has an antibody to a low incidence antigen that could not be detected with routine testing ?? 

That would be my first thought, at least.

[jayinsat]

There could be a number of reasons for this. My first thought is mom could have an antibody against one of the low frequency antigens (Cw, V, Diego, Bg, etc). If you really want to figure it out, you could perform an eluate on the cord blood and a select cell panel on the mom's plasma. You will need to run the cord eluate against that select panel as well. 

Of course, by select panel, I mean finding panel cells that are positive for the low frequency antigens.

That's my thoughts

 

[Malcolm Needs ☆]

I agree with both Bet'naSBB and jayinsat in that it is probably an antibody directed against a low prevalence antigen.  The problem with identifying the specificity of such an antibody is that there are so many!  To make certain that it is not a "fool's errand", it might be worthwhile trying to get a sample of blood from the putative father, if he is available and/or known.  As the baby is, like the mother, group O, there is a 50% chance that the father will also be group O, in which case it is simple to see if his red cells can be sensitised by a maternal antibody.  If he is not group O, everything is not lost as, as jayinsat suggests, an eluate from the baby's red cells should be clear of all anti-A and/or anti-B.
If the putative father's red cells are compatible by all methods, either there is another explanation for the positive DAT, or he is not the father (or both).

The other thing that springs to mind is that, even if there is an antibody directed against a low prevalence antigen, as you have not identified a specificity using your standard panel, and should the baby develop a clinically significant case of HDN (it is too late for HDF) and require a transfusion, acquiring crossmatch compatible blood, suitable for the baby, should be a simple task.

[Gkloc]

Update - We got a specimen from the father and ran an eluate from the Cord Blood with the fathers cells. The results of this were negative. We also found out that the mother gave birth in 2019 and the Cord Blood Workup for this infant was also O Rh Positive with a positive DAT.

[Neil Blumberg]

If the baby is not anemic and has no evidence for hemolysis, I'd just leave it at that.  There are variant plasma antigens that can elicit antibodies and these can be hard to identify using red cell serologic techniques. If the eluate is negative against panel red cells, this is high probability.  Perhaps mom is sensitized to a paternal immunoglobulin variant and these immune complexes are adhering to red cells.  There are no standardized tests for such anti-plasma protein antigens, to my knowledge.  Not very satisfying, but the clinical findings are the most important issues here, not the serologic issues.

[jayinsat]

I had this very scenario about a year ago and it turned out mom had an anti-Dia. It was not on any of our in lot screening or panel cells. I did as I suggested and ran a select panel against mother's plasma using expired panel cells and identified the Dia. The eluate on the baby was eluted the Dia also. 

Edited October 17, 2022 by jayinsat
edited for clarification

[Gkloc]

22 hours ago, jayinsat said:

I had this very scenario about a year ago and it turned out mom had an anti-Dia. It was not on any of our in lot screening or panel cells. I did as I suggested and ran a select panel against mother's plasma using expired panel cells and identified the Dia. The eluate on the baby was eluted the Dia also. 

I did forget to mention that I did do this prior to performing the eluate and testing against the Father's RBC's. I was able to find 8 low frequency antigens (Dia was included) but they all came out to be negative. Unfortunately that was all the low frequency antigens I could find on the panels that we have available here.

[AMcCord]

Just another thought (and I'm sure you also considered this), we see a positive DAT which doesn't seem to make sense a few times a year that is resolved by washing the cells an additional 3-6 times or by obtaining a capillary specimen on baby.

[SbbPerson ☆]

On 10/17/2022 at 5:44 AM, jayinsat said:

I had this very scenario about a year ago and it turned out mom had an anti-Dia. It was not on any of our in lot screening or panel cells. I did as I suggested and ran a select panel against mother's plasma using expired panel cells and identified the Dia. The eluate on the baby was eluted the Dia also. 

Do you do QC on your expired panels when you use them as selected cells? I was just curious. Thank you

[jayinsat]

On 11/5/2022 at 7:56 PM, SbbPerson said:

Do you do QC on your expired panels when you use them as selected cells? I was just curious. Thank you

Absolutely! It is in our policy in accordance with CAP and AABB standards.