The detection of platelet antibodies by simultaneous analysis of specific platelet antibodies and the monoclonal antibody–specific immobilization of platelet antigens: an interlaboratory comparison

Abstract

Glycoprotein (GP)-specific platelet (PLT) antibodies can cause allo- or autoimmune thrombocytopenia. Their detection is of high diagnostic value. The simultaneous analysis of specific PLT antibodies (SASPA) assay is based on simultaneous detection of various PLT-specific antibodies by flow cytometry and has entered routine use in our Mannheim institution. In this study, we performed an interlaboratory comparison investigation of PLT-specific antibodies using SASPA versus the "gold standard," the monoclonal antibody-specific immobilization of PLT antigen (MAIPA) assay. Sera from 194 patients with suspected PLT allo- or autoantibodies were tested against GPIIb/IIIa, IX, Ia/IIa, IV, and HLA Class I by SASPA (in Mannheim) and MAIPA (in Vienna). All data were reported blinded to those from the respective other method. Sensitivity studies included dilution studies with known antibodies against HPA-1a, -1b, -3b, -5b, and -15b and HLA Class I. Overall, results were concordant in 78.9%. The specificity and sensitivity of SASPA, based on the MAIPA results, were 97.3 and 86.3%, respectively, for the detection of alloantibodies. The respective results for the detection of autoantibodies were 95.3 and 44.9%. Serial dilution experiments with sera containing anti-HPA1a, -1b, -3b, -5b, and -15b and anti-HLA Class I revealed a higher sensitivity of the SASPA assay with all alloantibodies. In this first blind interlaboratory comparison, SASPA yielded similar results to those of MAIPA. The SASPA assay may be superior to the MAIPA assay for the detection of weak alloantibodies while simultaneous detection of a variety of antibody specificities or immunoglobulin classes and the need of fewer PLTs are obvious advantages.