Flow cytometry immunophenotyping and polymerase chain reaction-site-specific primers genotyping for HPA-1 alloantigens in an Italian blood donor population.

Background And Objectives: There is increasing interest in the development of rapid and reliable techniques for human platelet alloantigen (HPA) typing. This study investigates the reliability of flow cytometry for large-scale immunophenotyping of platelet alloantigens.

Materials And Methods: We used flow cytometry and polymerase chain reaction-site-specific primer (PCR-SSP) for the characterization of the human platelet antigen 1 (HPA-1) mosaic in blood donors.

Results: By using specific alloantisera and immunofluorescence labelling 9 (2.6%) out of 351 samples were HPA-1a-negative. To confirm this antigenic phenotype, all of the latter samples were submitted to PCR-SSP analysis, showing an HPA1-b/b genomic pattern. In HPA-1a-positive donors, flow cytometry was unable to distinguish HPA-1a/b heterozygous from HPA-1a/a homozygous subjects who were clearly identified by genotyping.

Conclusions: Flow cytometry is a valuable tool for large-scale screening to identify HPA-1a-negative persons, whereas genotyping is the assay of choice for zygosity testing, antenatal diagnosis, and for thrombocytopenic alloimmunized patients.