Flow cytometry beads rather than the antihuman globulin method should be used to detect HLA Class I IgG antibody (PRA) in cadaveric renal regraft candidates

Abstract
HLA Class I antibody screening can be performed by flow cytometry using a mixture of 30 distinct bead populations each coated with the Class I antigen phenotype derived from different cell lines. In this study we compared the efficacy of Class I antibody screens done by flow cytometry beads with the antihuman globulin (AHG) method for patients awaiting cadaveric renal retransplantation. Class I panel reactive antibody (PRA) screening by flow cytometric beads of 21 regraft serum samples that had all been found to be negative by AHG DTT Class I PRA, revealed that 57.1% (12 of 21) had a flow Class I PRA of ≥ 10%. Furthermore, when five regraft sera with an intermediate PRA were screened (mean AHG DTT PRA = 33.2 ± 13%) the mean flow Class I PRA almost doubled (mean flow PRA = 72.4 ± 10.2%) ( p < 0.01). When active UNOS waiting list regraft candidates, after several months of screening the Class I PRA by flow beads, were divided into the three PRA categories based on their peak flow Class I PRA value (0−20%, 21−79% and ≥ 80%), the incidence of a positive flow cross‐match was 0%, 72% and 85% and the incidence of retransplantation was 60%, 22% and 10%, in each of these groups, respectively. These data provided our histocompatibility laboratory with the rationale to stop performing the AHG PRA and perform only the flow Class I PRA method for regraft candidates.