Platelet antibodies identification: comparison between two laboratory tests

INTRODUCTION: Platelet antibody identification is indispensable for diagnosing the human platelet antigen (HPA) or human leukocyte antigen (HLA) immunization, mostly because it can restrict the compatibility and results of transfusions. Correct detection of these antibodies is of utmost importance for the diagnosis and treatment. METHOD: We present 16 platelet alloimmunization results, comparing two tests with different technologies: the MAIPA (monoclonal antibody immobilization of platelet antigens), as a reference technique, and a bead-based assay, the Pak-Lx. RESULTS: Eleven samples (68.75%) showed agreement in both techniques. Two tests were false negatives in the Pak-Lx: a pan-reactivity in GPIIbIIIa and an anti-HPA-9b. On the other hand, the Pak-Lx was more sensitive to detect a decreasing anti-HPA-5b. The Pak-Lx found an anti-HPA-2b positive, but with a low median fluorescent intensity (MFI), suggesting a false-positive result. Moreover, in one case, the MAIPA was negative for a positive Pak-Lx HLA. CONCLUSION: Antibody platelet diagnosis can sometimes be challenging. The methods seemed similar, the Pak-Lx being faster and simpler than the MAIPA, and they can be complementary to solve clinical issues.