Patient A neg, Ab Sc neg, DAT neg, Ab Id neg. IS incompatible then after a few minutes the incompatiblity disappears. Not rouleaux. gel Major Crossmatch incomp.

What is it?

What's the pt's diagnosis? Sounds like a cold ab to me. Have you let the plasma and cells sit together for "a few minutes" before spinning?

The patient has never had a transfusion before. He is 70, male. Previously in an outside hospital they could find compatible blood and they drew preop autologous. I advised the dr to perform Intraop Isovolemic Hemodilution tomorrow. He has.. hmmm what's it called, Spinal stenosis or something.. he is near paralysis

What do you mean .. how long and why and. at what temp should they sit together.

Dave, thank you for your prompt reply!

Liz

ah wait we used the polyspechic AHG for the major crossmatch. oh. I'll work with the IgG and tell you how it goes.

I agree with David.

I presume that the bag sample is sitting at 4oC prior to the ISXM, but, once it has warmed up to RT, hey presto.

Makes sense and the major crossmatch was done in the gel and Poly AHG so couldnt very well disperse. Thank you.

But, in the gel, I did incubate the donor rbcs and the patients serum at 37C before spinning. so it cannot be a cold. The gel AHG test was stronger than the IS.

But, in the gel, I did incubate the donor rbcs and the patients serum at 37C before spinning. so it cannot be a cold. The gel AHG test was stronger than the IS.

Yes it can Liz. We often find that an anti-M will give positive results by gel, but give negative results when performed strictly at 37oC. This is because sensitisation can occur very quickly in the cold (sometimes microseconds believe it or not), but dissociation (if that is the word for which I am looking) can take quite some time, even at 37oC, and sometimes the sensitisation can appear to be irreversible. Hence, if your plasma and red cells touch each other when they are cold, you get sensitisation, then you incubate at 37oC, and then you centrifuge again at room temperature, giving, albeit briefly, a second chance for the antibody to sensitise the red cells.

I assume this is happening with all units crossmatched?

It almost certainly is, but you would not necessarily detect it under normal circumstances, as the cells from the unit will be warmed, to a certain extent, by being put into the diluent that is being used, and not everyone has a "cold-reacting" auto- or alloantibody that reacts much above 4oC.

If, however, there is a "cold-reacting" auto- or alloantibody that reacts at, say 15 to 20oC, then you may well see this phenomenon and, because they are likely to be well-developed (as opposed to de novo) IgM antibodies, they "fit" their antigens very well (which is why they are difficult to dissociate).