The Seroprevalence of Anti-heparin-PF4 (Anti-HPF4) Antibodies Among COVID-19 Patients and Its Relevance to ICU Hospitalization and Mortality

Anti-heparin–platelet factor 4 (anti-HPF4) antibodies play a key role in heparin-induced thrombocytopenia (HIT). These antibodies can participate in thrombosis and mortality through platelet activation. HIT is a life-threatening complication. Recently, HIT has been reported as a risk factor of thrombocytopenia exacerbation in COVID-19 patients. In the present study, we assessed the incidence of anti-HPF4 in patients with COVID-19 and the relationship with ICU hospitalization and mortality. This cross-sectional descriptive study was performed on 97 COVID-19 patients in Yasuj City (Southwest zone of Iran). Demographic factors and platelet count, PT, APTT, and D-dimer were recorded and checked at admission and during hospitalization. Anti-HPF4 antibody assay was performed for all eligible patients by ELISA method. Statistical significance was based on two-sided design-based tests evaluated at the 0.05 level of significance. Most of the patients (n = 57, 58.8%) were male. The mean age of the patients was 55.46 ± 15.2 years, and the mean hospitalization was 17.57 ± 7.2 days. The mean length of stay was 209.9 ± 79.8 × 10³/µL. The results of the anti-HPF4 antibody assay showed that 9.3% (n = 9) of the patients were positive for anti-HPF4 antibody. The mortality rate was higher in the HPF4-positive patients. Although the true frequency of HIT in this study was unclear, it can be concluded that anti-HPF4 antibodies are involved in the pathophysiology of HIT which is a life-threatening complication in COVID-19 patients receiving heparin treatment, with a high rate of morbidity and mortality.