Hello Everyone,

 

I need help please with some cord results on twins.  Mom is O neg and displays anti-D, probably from her antenatal Rh immune globulin injection in March.  No extraneous reactions on her panel.

 

Twin A types group O.  We are unable to determine the Rh as he types weak-D positive but also has a positive direct coombs.  (Both 1+ in tube) We reported out his type as Undetermined. 

 

Twin B types O pos with a negative direct coombs. 

 

We repeated all testing, on lavender and the red tops received.  We tried washing the cells additionally.  I have anti-D reagent from Quotient and BioRad. Both gave the same results at immediate spin.  I didn't repeat the weak-D testing since the DAT is positive.  An eluate prepared from Twin A was all negative when tested with panel, A1 and B cells.  I also ran additional cells looking for a low frequency antigen.

 

I considered a mislabeled specimen but even if the samples were mixed up, we would still have the same results, just on the other twin.

 

If the antigen sites were blocked because of the DAT, shouldn't we have been able to elute anti-D? What should we try next?  Thanks in advance!

Why are you doing all of this testing?

you could try a mld heat elution at 56C to remove the ab.  The docs are going to treat the +DAT regardless of the etiology.  If the ag sites are blocked by anti-D your DAT would be a lot stronger than 1+.  Could also be a private ag from the father.

Auntie-D, since the mom is Rh negative we do a type and dat on the baby to see if she needs additional RhIG.  Excellent idea David thank you.  I agree, it's probably academic only at this point. I thought about drawing the father but again, it probably will not alter treatment. 

Auntie-D, since the mom is Rh negative we do a type and dat on the baby to see if she needs additional RhIG. 

 

Shouldn't a KB be the go-to to determine this. Until you have sent the samples for confirmation of Rh status the babies should be treated as Rh Pos and sufficient Anti-D issued. Further in-house testing on the babies is not required surely?

My guess is that this is due to anti-A.  I think the 'weak D' thing is probably just due to the weak pos DAT.  You should check the D type with monoclonal anti-D reagents.  and if the baby is Ok I would not worry about a 1+ DAT 

Anna

Shouldn't a KB be the go-to to determine this. Until you have sent the samples for confirmation of Rh status the babies should be treated as Rh Pos and sufficient Anti-D issued. Further in-house testing on the babies is not required surely?

 

You do a type first to see if you can do a rosette test!

Yes we start with rosette testing.  The baby is fine and the physician is not concerned.  I will try David's suggestion of a heat eluate.  Thank you all.

You do a type first to see if you can do a rosette test!

 

But the OP is stating they don't have a type - if the baby is weak-D then they should be treated as D-pos until D-status has been confirmed.

 

I think I clicked quote on the wrong bit - the OP was talking about doing elutions and allsorts. I just can't see why this is necessary. If the KB indicates a small enough bleed that the standard dose of anti-D is sufficient, why do we need to do all the rest? The physicians will manage the baby based on the chemistry results, not on the DCT strength as there is a poor correlation between strength of DCT and severity of HDN - a baby with quite severe HDN may only show a 1+ DCT, but one with mild HDN may shown 3-4+.

 

Or am I totally missing the point?