A RAPID FLOW CYTOMETRY ASSAY FOR HLA ANTIBODY DETECTION USING A POOLED CELL PANEL COVERING 14 SEROLOGICAL CROSSREACTING GROUPS1

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Many studies have demonstrated the usefulness of flow cytometry crossmatching (FC-XM) for selection of regraft recipients, and more recently this assay has been shown to correlate with allograft survival in primary cadaveric transplant patients. The need now exists for a practical antibody screening procedure which uses the same methodology. We describe here a simple and sensitive method to screen for HLA antibodies by FC using a pool of 6 cells selected to cover the 14 serological crossreacting groups defined by Rodey. Screenings of 367 sera (255 primary transplant sera, 112 regraft sera) received for monthly antibody testing were performed by both pooled cell FC and complement-dependent cytotoxicity (CDC) assays. Forty of these sera were also FC-screened using a panel of 16 individual cells for comparison with the pooled cell FC screenings. Analysis indicated a strong correlation between the pooled FC-PRA and the individual cell panel FC-PRA (P = .0001) with mean values of 60% and 73%, respectively. Only 2 of the 40 sera screened by both FC methods resulted in PRAs that differed by > 40%. The majority (82%) of the primary patients did not exhibit HLA antibodies by CDC--however, 22% of the CDC negative patients were positive by flow cytometry. Females were more likely to be positive by FC (35%) than males (16%) (P = .0001). Similarly, black patients were more likely to have FC-demonstrable antibodies (28%) than white candidates (14%) (P = .014). The regraft patients who tested positive by either or all methods had a mean PRA for CDC, pooled FC-PRA, and individual cell FC-PRA of 40, 75, and 85, respectively. FC-PRA proved to be a more sensitive technique in both primary and regraft patients.