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Johnv

VISION ABD GEL CARD NOT REACTIVE WHEN ANTI A1 IS PRESENT

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We had a recent example where the patient has anti-A1 but the A cell well on the Ortho ABD gel card was clearly negative on the Vision.  It was discovered when two A positive units were crossmatch at initial spin and they were +4!  Two O Pos units were crossmatched and they were negative or compatible at immediate spin.  Testing in tubes with Immucor A cell gave +2 A cell at initial spin.  When testing the patient cells with A1 lectin the result was negative and repeating the reverse with A2 cells the result was negative.  In addition, a  cold panel indicated a cold antibody was present.  The Ab Screen was negative and we crossmatched the units to AHG and they were negative.  Has anyone else seen this situation?    

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Posted (edited)

Based on an observational study of ABO grouping in Gel I reported at the 1997 AABB Annual Meeting, ABO Plasma Grouping discrepancies occurred in 0.8% (26/3183) adult ABO grouping tests in Gel.  Anti-B was not detected in 24/26 patients, anti-A was not detected in 2/26 patients, and anti-A1 was not detected in 3183 patients.

In comparison, anti-A and anti-B was detected in 19/26 patients by the immediate-spin tube test, and was detected in 7/26 patients after 10 minute incubation room temperature incubation and centrifugation.

Based on this study and 20 years of gel testing since that time have shown me the anti-A1 is rarely detected in Gel and that 70-80% of ABO plasma grouping discrepancies are resolved using the immediate-spin tube test.  

Centrifugation is used quite differently in gel versus tube testing. Centrifugation is used to separate agglutinated cells from un-agglutinated cells within the gel column, but is used to enhance agglutination in standard tube tests by forcing cells together at the bottom of the tube.  This may contribute to the increased sensitivity of tube testing in ABO Plasma grouping tests.

Edited by Dansket
clarify and added sentence at end

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