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Strong Anti-D after Rhogam


saralm88
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Hi everyone!

I hope everyone had a nice summer!  I have a confusing scenario going on.  I have a mom who received 2 doses of Rhogam (one for spotting and the other at 28 weeks) and upon delivery, I am picking up a strong Anti-D on the baby's cells and I did a titer on mom and it is 1:512.  Anyone ever experience something like this before?  I deal with a lot of Rhogam and this is a first for me :(.

 

Thanks!

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Thank you Malcolm!  We have done an exchange on the baby but now I am completely confused - one of my seasoned techs just did a quick few D+ cells on mom and she is getting barely weak reactivity.  Needless to say - a redraw is happening.

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I wouldn't expect to see many D Positive red cells in the mother's circulation.  Any such red cells can only have come from the baby, and these would have been sensitized by the maternal anti-D and immediately removed from the maternal circulation by her own reticuo-endothelium system.  It is very likely that the mother was sensitized to produce an immune anti-D by a foeto-maternal haemmorhage quite early in her pregnancy for this baby to be so badly affected, possibly with a chronic FMH further into the pregnancy.

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12 hours ago, richj said:

I think saralm88 is saying that the Mom's plasma vs D+ cells is barely reactive. Where is the high titer Anti-D?

Oh, sorry, I misunderstood.

An anti-D with a titre of 512 is pretty high (not the highest I have ever seen, by any means, but pretty high.  An anti-D with a titre of 512 is quite capable of forming blocking, by swamping the D antigen sites on the red cells, even with the use of AHG.  This could be the answer (it may not be, but it could be).

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There is clearly a problem here.  If you did a titre on a D+ cell and it was 512 then the antibody should be coming up quite strongly positive against ALL D+ cells unless......

1.  this is not an anti-D but another antibody and you were just lucky that you hit the spot when you did the titre (or maybe a weak anti-D + an anti-LFA)

2.  Technical error during the titre

3.  technical error during the 'quick few D+ cells on mum

4.  Mum has been plasmapheresed inbetween you doing the titre and the 'quick few D+ cells

5.  The titre is actually now higher than 512 and you are seeing a prozone effect

 

I suggest you re-test the cell you used for the titre, plus do a panel - and look for anti-LFA

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  • 1 year later...
On 8/31/2017 at 8:03 AM, saralm88 said:

Thank you Malcolm!  We have done an exchange on the baby but now I am completely confused - one of my seasoned techs just did a quick few D+ cells on mom and she is getting barely weak reactivity.  Needless to say - a redraw is happening.

Could it also be that because the baby has been delivered that the Anti-D crossed the placenta and has coated the baby's RBCs? This might cause a decrease in reactions if there is not the same amount of antibody to detect?!?

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