Sensitive detection of platelet-specific antibodies with a modified MAIPA using biotinylated antibodies and streptavidin-coated beads

We have developed a modified monoclonal antibody immobilization of platelet antigens assay (MAIPA) with enhanced sensitivity in detecting antibodies against human platelet antigens (HPA), using biotinylated monoclonal antibodies, streptavidin-coated beads and detection by flow cytometry. The beads-MAIPA gave superior signal-to-noise resolution (> 10-fold higher) for detection of anti-HPA-1a and anti-HPA-5b compared with the in-house standard MAIPA. Also, efficient and reproducible detection of anti-HPA-15 (CD109) was shown. The enhanced sensitivity was confirmed using WHO International Reference Reagents for anti-HPA-1a, anti-HPA-3a and anti-HPA-5b, which allowed comparison of detection endpoints with other laboratories. Finally, the beads-MAIPA was validated for quantification of anti-HPA-1a. The lower limit of quantification was 0.4 IU/mL for beads-MAIPA, compared to 1 IU/mL previously reported for standard MAIPA. Based on improved performance against all HPA-antibodies tested, the beads-MAIPA has replaced the standard MAIPA in our laboratory in diagnostics of conditions due to HPA-immunization, such as fetal and neonatal alloimmune thrombocytopenia (FNAIT).