Discrepant Antibody Testing Results: Which One to Believe?

The impact of solid-phase immunoassay for HLA antibody detection on the field of transplantation has been extremely significant by providing the most sensitive and precise method for characterization of HLA antibodies. However, despite all the benefits, technical limitations and inherent artifacts represent significant challenges, particularly with Luminex-based single-antigen bead (SAB) assay. Discordant results between antibody detection (screening assay) and identification (SAB) is not uncommon. Positive SAB assay in the context of negative screening testing is well documented and attributed to altered tertiary structure of HLA molecules exposing new epitopes or detection of naturally occurring antibodies. However, there are few reports that addressed the opposite scenario when negative SAB appeared in the context of positive screening assay. In such discrepant results, unmissed HLA antibody has to be excluded with certainty by other tests; however, with the availability of variable assays it may be difficult to choose the best combinations that clarify discrepancy without adding more confusion. Here we describe the results of correlation between 2 antibody screening solid-phase immunoassays (LABScreen Mixed using Luminex and FlowPRA Screen) on conventional flow cytometry and compare their outcomes with SAB and crossmatch results.