Detection of HLA class I and II antibodies by ELISA and complement-dependent cytotoxicity before and after transplantation

Background Anti class I IgG can be detected by complement-dependtent cytoto xicity (CDC) and by ELISA. We compared ELISA and CDC for both class I and c lass II antibodies oil method agreement and relation to rejection-free ar;i d graft survival. Methods. Peak, current, and posttransplant sera (n=429): of 143 renal allog raft patients were tested by National Institutes of Health technique (NIHT) , two-color fluorescence (TCF), and ELISA. Method agreement was assessed by intraclass correlation coefficient (ICC), Rejection and graft survival wer e analyzed by uni- and multivariate techniques. The screening results for e ach serum were compared, as was the change in result of current to posttran splant serum. Results, The ICC of ELISA and NIHT was insufficient; it was lower for TCF t han NIHT, Graft survival was not related to the result of any assay. Reject ion-free survival was related to ELISA and NIHT in current and posttranspla nt serum. With the NIHT, the change in percent panel-reactive antibody (%PR A) correlated better with rejection than it did with ELISA. The combined an tibody status of current and posttransplant serum was a risk factor for rej ection in all assays, and for TCF also in multivariate analysis. The reject ion rate was higher if the posttransplant serum was ELISA-negative/CDC-posi tive, rather than ELISA-positive/CDC-negative. For ELISA, class I specifici ties land not %PRA) in peak and current sera were related to rejection, eve n if the antibodies were not donor-directed. In the case of the National In stitutes of Health technique (NIHT), %PRA and not specificity was related t o rejection. Class II antibodies were never related to rejection. Conclusions. ELISA and NIHT are complementary screening techniques in this patient population. They are of equal predictive value for rejection The op timal strategy in combining these techniques must be determined.