Lymphocytotoxicity crossmatch proficiency testing among regional transplant centers

During an eight and a half-year period (1976-1984), 408 combinations of different cells and sera involving 12,652 lymphocytotoxicity crossmatch reactions performed by 21-37 histocompatibility laboratories were studied in 20 proficiency tests conducted by the South-Eastern Organ Procurement Foundation. Consensus by 75% or more laboratories were obtained on 336 (82.4%) of these test samples: of the 10,410 reactions examined with the use of these consensus cells and sera, only 649 (6.2%) were discordant. Considering positive and negative reactions separately, the discordant (false) positive and negative rates were similar (6.1%, 6.4%, respectively). Varying specific factors in given tests indicated that discordant results were significantly reduced by (1) dispensing sera in trays centrally rather than locally; (2) using a standard one-wash procedure rather than local or three-wash methods; and (3) using reagent (monospecific) rather than patient (polyspecific) sera. Use of standard versus local rabbit complement did not significantly influence the concordance of results.