Managing patients with "not so black and white antibody screen" results

A Transfusion Service Supervisor at a hospital in Maryland reports that she would appreciate feedback regarding how other blood bankers manage patients with a "not so black and white antibody screen" result. She has reviewed the previous e-Network Forum discussion "Should an AHG crossmatch be performed on a patient with a positive Gel-AHG antibody screen, but a negative or equivocal Gel-AHG panel?", but would still like feedback. Her institution has been using both GEL AHG and tubes with PEG since 2004 and they have seen many examples of a GEL-AHG screen with a 1+ strong result with one or more screening reagent red cells, but then absolutely negative in a panel using the GEL-AHG method. They would repeat the screen using tubes with PEG and get a negative screen and wonder what to "call" it. She acknowledges that they occasionally get GEL-AHG screen with a "funny" weak reaction, that would not be reproducible upon respinning the sample to get rid of possible fibrin. However, if the repeat GEL-AHG screen was still positive, they would do the GEL-AHG panel. If it was inconclusive, they would call the results non-specific and do a full Coombs crossmatch. If the panel was negative, they would call the screen negative and do immediate spin crossmatches. Does anyone else do it that way? The inquiring colleague hates to have to tag a patient with an antibody if the patient does not have a clinically significant one. She would like to just repeat the screen in tubes with PEG and let it go as negative, but she has also seen a patient with anti-S in gel only and an anti-e that appeared to be an auto anti-e only in gel. She concludes with the hope that automation will make it easier to decide what to do with these types of cases. Maybe the instrument will "decide" if it's positive?

The following comments have been submitted in response:

ADDENDA July 14, 2009

1. A colleague who works in Central California reports that at his hospital, the experience with manual versus automated GEL testing had been similar to that described by the Transfusion Service Supervisor at a hospital in Maryland, i.e., a signficant percentage of patients have a weakly positive antibody screen (1-2+) with a negative panel, but more often a positive panel with one or more panel cells agglutinated, in which specific antibody could not be identified. In his experience, patients presenting with these findings are routinely provided antiglobulin-crossmatch compatible red blood cells. Currently, his laboratory will subject these blood samples to three centrifugations using the 3-minute setting of a StatSpin® Express 3 centrifuge (4400g+). Re-testing the centrifuged plasma produces negative antibody screens in some cases.

ADDENDA July 28, 209

2. Dr. Joan Cid of the University Hospital in Tarragona, Spain (attribution used with permission) comments that LISS tube IAT is the classical laboratory technique that has been used for several years at his institution. Their experience has been that column agglutination systems are as good as, or better, than this conventional tube agglutination system. However, sometimes, the gel tests produce false positive results and they need to come back to the tube test to be sure that they are not in front of a clinically significant antibody. There is a lot of literature about this topic and he would like to share with the e-Network Forum his paper published in Transfusion Medicine 2006;16:131-6.
   
   
3. A colleague at a university affiliated hospital in the Sacramento area reports that they occasionally see GEL screens (manual or automated) with a 1+ result for one cell only, but no reactivity in a GEL panel. They then go on to run a 2 cell PeG screen with autocontrol. If the PeG screen and autocontrol are negative, they call the original GEL screen reactivity "non-specific agglutination (NSA)". However, as a precaution they crossmatch random RBC units using the AHG method with PeG enhancement. In such cases they sometimes see fibrin on top of the GEL wells and by respinning the plasma with repeat testing in GEL, often the reactivity goes away. The responding colleague thinks some of the reactivity they see in GEL might be rouleaux, but she does not know how to confirm that hypothesis.
   
   
4. The head of a University Hospital Blood Bank in Buenos Aires reports that they have had a similar case recently. They use the Diamed™ GEL manual LISS/Coombs cards with a panel of 2 red blood cells. The patient reacted on this but not on the larger panel of 14 cells. They report being told by Diamed, Switzerland, that some red blood cell donors from the smaller panel present a "private antigen" that very seldomly react with serum from patients and this antigen is absent in the larger panel. They advised that the testing be repeated with a different lot of the panel of 2 red blood cells.

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