Detection of HLA antibodies by using flow cytometry and latex beads coatedwith HLA antigens

BACKGROUND: Detection of HLA class I antibodies in sera is needed in variou s clinical situations. The standard method for detecting HLA class I antibo dies is the complement-dependent lymphocytotoxicity (CDC) assay, but solid- phase assays are now available. STUDY DESIGN AND METHODS: This study assessed the ability of a flow cytometric as say using latex beads coated with HLA class I antigens to detect HLA class I-specific antibodies. The CDC assay was compared with the pooled-bead assa y for the detection of HLA class I antibodies. Thirty-one randomly selected serum samples previously tested by CDC assay were tested with pooled beads and analyzed by flow cytometry. Twenty-seven additional serum samples, cho sen by clinical criteria and CDC assay results, were tested against the poo led beads. Next, samples from six patients from whom three or more serum sa mples were drawn on consecutive days were tested with both methods. Finally , serum samples that were proved positive by both methods were tested with selected beads coated with antigens from a single person. RESULTS: Among the randomly selected serum samples, there was 90-percent ag reement between the two assays. There was 96-percent agreement between the two assays of the 27 samples that were selected by clinical criteria and CD C assay results. Testing the sera with individual beads suggested that the HLA class I antibodies react with beads expressing the corresponding HLA an tigen and beads expressing antigens in the same cross-reactive group. CONCLUSION: The pooled-bead assay can be used as an alternative method for detecting HLA class I antibodies. However, if the specificity of the HLA cl ass I antibody is required, another assay must be used.