Impact of Uniform Methods on Interlaboratory Antibody Titration Variability: Antibody Titration and Uniform Methods

Context.—Substantial variability between different antibody titration methods prompted development and introduction of uniform methods in 2008. Objective.—To determine whether uniform methods consistently decrease interlaboratory variation in proficiency testing. Design.—Proficiency testing data for antibody titration between 2009 and 2013 were obtained from the College of American Pathologists. Each laboratory was supplied plasma and red cells to determine anti-A and anti-D antibody titers by their standard method: gel or tube by uniform or other methods at different testing phases (immediate spin and/or room temperature [anti-A], and/or anti-human globulin [AHG: anti-A and anti-D]) with different additives. Interlaboratory variations were compared by analyzing the distribution of titer results by method and phase. Results.—A median of 574 and 1100 responses were reported for anti-A and anti-D antibody titers, respectively, during a 5-year period. The 3 most frequent (median) methods performed for anti-A antibody were uniform tube room temperature (147.5; range, 119–159), uniform tube AHG (143.5; range, 134–150), and other tube AHG (97; range, 82–116); for anti-D antibody, the methods were other tube (451; range, 431–465), uniform tube (404; range, 382–462), and uniform gel (137; range, 121–153). Of the larger reported methods, uniform gel AHG phase for anti-A and anti-D antibodies had the most participants with the same result (mode). For anti-A antibody, 0 of 8 (uniform versus other tube room temperature) and 1 of 8 (uniform versus other tube AHG), and for anti-D antibody, 0 of 8 (uniform versus other tube) and 0 of 8 (uniform versus other gel) proficiency tests showed significant titer variability reduction. Conclusion.—Uniform methods harmonize laboratory techniques but rarely reduce interlaboratory titer variance in comparison with other methods.