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Screen pos, xmatch neg?


K@The_Dresdeners

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Hello everybody,

We can´t find out the antibody...

Pts blood group is A1D CcD.ee K-, Anti-AB 4+, Anti-A 4+, Anti-B neg, Auto neg., Anti-A1(lectin) 4+ Anti-H neg. (backward: 3+ with B-Cells, negative with 0-, A1-, A2-cells)

IAT, Papain and CaptureR screens are positive at 37°C/ 3+ with all cells, IAT screen at room temperature 4+ (gel column cards, BioRad and Grifols)

Antibody identification was done in IAT 37°C (3+ with all cells), DAT weak+

IAT screen with washed cells 3+

But... in xmatch with RBCs from bloodbags (PAGGS-M): A1D CcD.ee K-, A2D CcD.ee K- and 0D CcD.ee K- all negative in IAT 37°C /gel column cards

Can anybody help me out?

Thanks,

K.

 

 

 

 

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Oh, I'm sorry, I wasn't criticizing; after all, I cannot either speak or write a word of German!

If you were cross-matching group A red cells, whilst your panel cells were group O, it sounds very likely that the patient has an auto-anti-H.  The reason I say this is because the H antigen is very strongly expressed on group O red cells, but very weakly expressed on group A red cells, and your reactions are exactly what I would expect to see in such a case.

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OK, so I presume you are  diluent 2 to make your crossmatch suspensions?  Well, Diluent 2 is not identical to the buffer used for the cell suspension in the screening cells.  so it may be that this patient is reacting against something in the red cell suspension buffer which is common to both biorad and Capture - although I have never seen one reacting that strongly before.

On the other hand, it certainly does look like a cold antibody.  Are you doing both screen and XM manually or on an instrument?  And how exactly are you preparing your blood bag segments?

 

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Looks like an interfering substance to me.  Have you tried rinsing your screening cells with diluent (1x is usually sufficient), re-suspending those cells in diluent, then re-testing in gel to see if the reactions go away?

 

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So you put them in a tube, but you don't centrifuge them.  Is that right?  If so, look at the cell pellet at the bottom of the well.  In my experience, not centrifuging the segment can mean that your suspension is weaker than it would be if you were using a spun patient sample (or the reagent red cells) because your 5ul is not 5ul of packed red cells.  when weak reactions are involved, a weak suspension can make a weak positive reaction look negative.

This could mean that actually the crossmatch results were falsely negative

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In that case, I strongly suspect that Anna's (galvania's) suggestion about an antibody to a bacteriacidal additive used to suspend the screening and antibody identification panel red cells is correct.  Way back, I experienced this myself, and even if the cells were washed about 4 to 6 times, I could still not get rid of the positive reactions.

I always used to suspend my red cells in Dil2, until I was told to stop it by one of my bosses on the grounds that it was too expensive.  After that, we saw it more and more, and, of course, it actually cost us more to sort out the problem, than it would have done if we had continued to use Dil2.  Bosses who wear suits, rather than white coats, always know best though!

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