Semiautomation of platelet HPA-1a phenotyping by SPRCA and ELISA

An enzyme-linked immunosorbent assay (ELISA) and solid phase red cell adherence assay (SPRCA) were assessed for platelet HP-1a typing in U well microplates. Both methods were partially automated by the use of the Tecan RSP 8051ID robotic sampler and the SLT 400 ATC plate reader with Soft2000 software. Pretreatment of the adherent platelets with chloroquine diphosphate or citric acid enabled anti-HPA-1a, even when contaminated with HLA class 1 antibodies, to be used for typing. Of 675 antenatal samples, 13 were identified as HPA-1a negative. A further 36 known donor HPA-1a negative samples were correctly typed by both methods. Concordant results were obtained for the ELISA and SPRCA. All presumed HPA-1a negatives were confirmed by either polymerase chain reaction using sequence-specific primers (PCR-SSP) or by monoclonal antibody-specific immobilization of platelet antigens (MAIPA). The two semiautomated systems provide simple, accurate, reproducible, and secure ways for large scale HPA-1a phenotyping. The SPRCA can also be performed as a manual technique for small batches of samples.