Antihuman Leukocyte Antigen–Specific Antibody Strength Determined by Complement-Dependent or Solid-Phase Assays Can Predict Positive Donor-Specific Crossmatches

Context.—The association of circulating donor-specific antibody (DSA) strength with crossmatch results is of potential interest to predict allograft outcome. Objectives.—To systematically investigate the aforementioned association and to attempt to define a cutoff value for DSA strength that can predict a positive crossmatch result. Design.—We analyzed DSA strength and crossmatch results from the 2006 to 2008 proficiency testing samples of the American Society of Histocompatibility and Immunogenetics (n = 50). We further validated our findings in candidates for potential kidney transplant (n = 19). Results.—Proficiency test samples with positive antihuman globulin T-cell crossmatch results had significantly higher DSA strength, as assessed by Luminex (Austin, Texas) mean fluorescent intensity (MFI; MFI [SD], 7860 [4770]), compared with samples with negative crossmatch results (MFI [SD], 2900 [1820]; P = .001). Similarly, higher Luminex values were observed in samples from candidates for transplant with positive antihuman globulin T-cell crossmatch results (MFI [SD], 7910 [2370] versus 2840 [1960]; P < .001). The MFI value of 6540 had 61% and 75% sensitivity and 92% and 94% specificity for predicting positive antihuman globulin T-cell crossmatches in proficiency test samples and in candidates for transplant, respectively. Conclusions.—The DSA strength correlates well with crossmatch results. An MFI of 6540 predicted a positive antihuman globulin T-cell crossmatch.