Abstract: Objective In order to explore whether there are PF4 antibodies in patients with thrombocytopenia and affect platelet function. Methods Serum samples were randomly collected from thrombocytopenic patients referred for specialized platelet cross-matching and from healthy donors, P latelets from donors of the same blood group were randomly selected as target cells. Anti-PF4 antibodies were screened by enzyme-linked immunosorbent assay (ELISA), and positive samples were retested with heparin supplementation. Anti-PF4+ samples were further analyzed for the coexistence of other antibodies. Normal platelets treating with incubated with anti-PF4+ samples, followed by assessment of platelet function via thromboelastography (TEG) and analysis of platelet activation levels using flow cytometry. Results Among 107 patients with thrombocytopenia, 12 (11.42%) were positive for anti-PF4, including 3 showing heparin inhibition and 8 presenting with concurrent non-PF4 antibodies. TEG analysis revealed lower platelet aggregation in 1/12, mixed aggregation patterns in 2/12, and higher aggregation in 9/12. Flowcytometry demonstrated a higher proportion of CD41a+CD62p+ platelets induced by anti-PF4+ sera than that by healthy donors (23.05%±4.88% vs 14.09%±3.24%, P<0.001). Conclusion Anti-PF4 antibodies are present in a subset of thrombocytopenic patients, and exhibit significant functional heterogeneity, which may exert diverse effects on platelet transfusion outcomes.

Key words: Thrombocytopenia, Platelet transfusion, Anti-PF4 antibody, Thromboelastography, Platelet aggregation