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COMPLEMENT POS DAT AND FULL CROSSMATCH


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We have a new tech training in blood bank and I have an old Case Studies packet I give towards the end of the training.  One of the results for interpretation is a clean type, neg antibody screen and a DAT with a positive complement result.  The crossmatch has immediate spin results and the "answer" key indicates that a full crossmatch should be done in this circumstance.  Now years ago, with serum samples and performing a DAT with every spec... I remember this being done if the patient had been transfused in the last __?__ weeks.  Now we're testing patient's plasma so...  Can anyone refresh my memory please?

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I can't refresh your memory, but I do know of a case of anti-Vel in the UK that caused a fatal transfusion reaction.  The DAT was positive by anti-complement only, and the anti-Vel itself could only be detected in a clotted sample, not in an EDTA sample.

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So Malcolm, do you see any need to do a full crossmatch if say, the patient was transfused in the past two weeks (antibody mopped up, so negative antibody screen but hgb dropping and only complement pos DAT )?  I know this is far fetched with EDTA spec but this new tech is really smart...and I'm having trouble keeping up.

  

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Trying yes - but the anti-IgG DAT is negative so...not that this hasn't happened to be helpful before in a full IRL workup but we are in front of the patient and need to transfuse ASAP.  A full crossmatch would be much quicker.

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18 minutes ago, jnadeau said:

Trying yes - but the anti-IgG DAT is negative so...not that this hasn't happened to be helpful before in a full IRL workup but we are in front of the patient and need to transfuse ASAP.  A full crossmatch would be much quicker.

I have cited this reference over and over and over again.  Sachs UJH, Röder L, Santoso S, Bein G.  Does a negative direct antiglobulin test exclude warm autoimmune haemolytic anaemia? A prospective study of 504 cases.  British Journal of Haematology 2006; 132: 651-661, and it refers to transfusion reactions too.

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19 hours ago, Malcolm Needs said:

I can't refresh your memory, but I do know of a case of anti-Vel in the UK that caused a fatal transfusion reaction.  The DAT was positive by anti-complement only, and the anti-Vel itself could only be detected in a clotted sample, not in an EDTA sample.

Those anti-Vels are sneaky !

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For our procedure, we would perform a Cold Antibody Screen. If it is panreactive, then the patient is suspect to have a Cold Auto Antibody.  We would only give electronic crossmatch. If it is selectively reactive, we would perform a cold panel to identify the cold antibody and give antigen negative for the clinically significant antibody.

 

We used to do immediate spin crossmatch a few years back but it almost always positive due to the cold auto, which would reflex to full crossmatch.  Our medical director changed the process.

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  • 2 weeks later...

We frequently get samples on recently transfused patients that the hospital says have a negative DAT. Our DAT in Gel will be +/= and maybe a few +/= reactions in the neat plasma. The eluates often have easily identified antibodies with strengths up to 3+ in Gel. When we call the hospital to give report, we have been told several times that they gave crossmatch compatible blood before our work was complete. We sometimes perform eluates on negative DAT samples if it "makes sense" to us. Usually it's when we say to ourselves, "This might be a weak warm-auto if the DAT were +".

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