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Prewarm ABO

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Hi, when you do a prewarm ABO due to cold agglutinin interference, do you also do a prewarm QC to ensure that your ABO antisera are working at 37C? Please advise!

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What we do is wash the red cells of the patient's sample multiple times with warm saline.  Then we would use the ABO antisera at 37oC with positive and negative controls at the same temperature.

The problem comes with the reverse grouping.  If the "cold" auto-antibody has a wide thermal amplitude, it may be necessary to use cord cells at 37oC, if you can get hold of them.  In the UK, this is no longer easy, as we have to get written consent from at least one of the parents.

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Devil's Advocate Asks:  If we establish that the reason for the reactions in the backtype are due to cold agglutinin(s), why are we pre-warming ABO tests?   Pre-warm = 37C reacting antibodies.  If this is a valid alternative to RT/I.S. Crossmatch, then shouldn't we be performing an Extended Crossmatch (37C to AHG) to look for the IGG versions of the ABO Antibodies?

Simple Answer: Immediate Spin Crossmatch:  If due to cold agglutinin (other than ABO) = Compatible by Blood Type.

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21 minutes ago, JPSCANNELL f. CROKE said:

Devil's Advocate Asks:  If we establish that the reason for the reactions in the backtype are due to cold agglutinin(s), why are we pre-warming ABO tests?   Pre-warm = 37C reacting antibodies.  If this is a valid alternative to RT/I.S. Crossmatch, then shouldn't we be performing an Extended Crossmatch (37C to AHG) to look for the IGG versions of the ABO Antibodies?

Simple Answer: Immediate Spin Crossmatch:  If due to cold agglutinin (other than ABO) = Compatible by Blood Type.

Well, for the simple reason that 1) you have to prove that the reverse grouping anomaly is really just due to the "cold" auto-antibody, and not to something else, and 2) that there is no clinically significant atypical alloantibody being masked by a "cold" auto-antibody of wide thermal amplitude.

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6 hours ago, Malcolm Needs said:

Well, for the simple reason that 1) you have to prove that the reverse grouping anomaly is really just due to the "cold" auto-antibody, and not to something else, and 2) that there is no clinically significant atypical alloantibody being masked by a "cold" auto-antibody of wide thermal amplitude.

True! I was once doing a workup that had both an ABO discrepancy and a positive screen, and they had to be treated as separate issues unless later proved related. Prewarming failed, so another tech following up after my shift had to use cord cells to clean up that mess. The antibody ended up being a non-specific CAA.

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Hmmm...  Never have used the prewarm technique to resolve a forward type.  Just "thinking out loud":  In the scenario of a cold interfering autoantibody, prewarming is typically used to prevent "free" cold autoantibody from binding onto red cells causing unwanted reactivity.  In testing a patient's red cells, there should be no "free" autoantibody present if the sample was adequately washed.   The issue with the forward type is the antibody that is already bound to the patient's cells.  If warm washing did not remove it, then I'm not sure how prewarming the forward type would be more effective.  If it works though, great!  Whatever it takes to resolve ABO discrepancies due to cold autoantibody interference, I'm for it!

We warm wash the patient's cells with 37C saline.  If needed, move to a form of heat elution (incubate or even wash with 40-45C saline) and if that's not effective, treat the cells with 0.01M DTT (treated controls must be included).  Reverse type resolution: I- cells, prewarm at 37C spin, and just recently, resolved a back type issue with testing at 37C/AHG with heavy chain specific anti-IgG.

I'm sure I don't need to say this, but I'm going to anyway:  In a situation where you have an unresolved ABO discrepancy and you have to transfuse, don't guess.  Give group O red cells.

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