Diagnostic accuracy of solid phase HLA antibody assays for prediction of crossmatch strength

Solid phase antibody assays are increasingly used to provide quantitative measures of donor-specific HLA antibodies for assessment of pretransplant risk, although cell-based crossmatches continue to serve as gold standards for determination of donor HLA antibody strength. This study determined the ability of HLA antibody solid phase assays to predict the strength of cell-based flow cytometric (FC) and complement-dependent cytotoxicity (CDC) crossmatches. Eighty-two recipient/donors pairs were analyzed using receiver operating characteristic (ROC) curve analyses to determine the accuracy of donor-specific median fluorescence intensity values (Σ MFI) from single antigen bead assays for predicting strong FC and CDC crossmatches. Diagnostic sensitivity and specificity of optimal Σ MFI values were highest for predicting strong T cell FCs. Σ MFI values showed good sensitivity for predicting positive direct and AHG-augmented CDC crossmatches (91% and 94%, respectively), but with lower specificity (67% each). Specificity and sensitivity for predicting positive B cell CDC crossmatches were 73% and 84%. Σ MFI values derived from single antigen bead assays can predict strong flow and positive CDC crossmatches, but with tradeoffs between sensitivity and specificity. The results support the use of solid phase assays for quantitative virtual crossmatching and as a replacement for cell-based crossmatching.