A rapid and specific whole blood HPA-1 phenotyping by flow cytometry using two commercialized monoclonal antibodies directed against GP IIIa and GP IIb-IIIa complexes.

The human platelet antigen 1 (HPA-1) system has been implicated in rare but severe diseases, such as neonatal alloimmune thrombocytopenic purpura, post-transfusion purpura and immune platelet refractoriness. We developed a flow cytometry assay for HPA-1 phenotyping using two commercial monoclonal antibodies, P2 and SZ21, directed against glycoprotein (GP) IIb-IIIa and GP IIIa respectively. One hundred and twenty-seven healthy controls were studied and ratios of mean fluorescence intensity for P2 and SZ21 discriminated between HPA-1a homozygotes and heterozygotes. These two monoclonal antibodies, coupled with flow cytometry represent a rapid and reliable tool for platelet HPA-1 typing to aid diagnosis.