Two-stage papain-indirect antiglobulin test and LISS direct agglutination are not appropriate for pretransfusion screening for unexpected antibodies.

BACKGROUND: The screening for unexpected antibodies has proved to be a suitable pretransfusion compatibility method, but controversy still remains regarding the most appropriate serologic techniques to use in such a screening and, in particular, whether or not to use enzyme-based methods.

METHODS: Over a period of three years, 27,149 patient sera submitted to pretransfusion testing were screened for unexpected antibodies. Serologic techniques included LISS-direct agglutination (DAG) reading plus indirect antiglobulin test (IAT), and two-stage papain (2SP)-IAT.

RESULTS: In all, 592 (2.18%) serum samples yielded a positive result. Further studies of these specimens disclosed 466 alloantibodies in 371 cases, and 221 unwanted positive reactivities. 2SP-IAT and LISS-DAG allowed the detection of 124 alloantibodies missed by LISS-IAT (78 anti-Lewis, 33 anti-E, 7 anti-P1, 2 anti-K1, 2 anti-K3, 1 anti-M, 1 anti-Cw), but were responsible for 81% of the unwanted positive reactivities.

CONCLUSIONS: Since most alloantibodies detected only by 2SP-IAT or LISS-DAG were of doubtful clinical significance, and these techniques produced a high number of unwanted positive reactivities, we conclude that 2SP-IAT and LISS-DAG are not appropriate for the pretransfusion screening for unexpected antibodies.