Antiphospholipid antibodies in convalescent plasma of donors recovered from mild COVID‐19 infection

Abstract Background and Objectives Passive immunization by the infusion of convalescent plasma (CP) obtained from patients who have recently recovered from COVID‐19, thus having antibodies to severe acute respiratory syndrome coronavirus 2, is a potential strategy to reduce the severity of illness. A high prevalence of antiphospholipid antibodies (APLA) in patients with COVID‐19 has been reported during the pandemic, raising a concern whether the use of CP could increase the risk of thrombosis in transfused patients. We aimed to evaluate the prevalence of APLA in COVID‐19 CP (CCP) in order to assess the potential prothrombotic influence of transfused CCP to COVID‐19 patients. Materials and Methods We studied the prevalence of APLA in 122 CCP samples collected from healthy donors who recovered from mild‐COVID‐19 at two time periods: September 2020–January 2021 (defined as ‘early period’ samples) and April–May 2021 (defined as ‘late period’ samples). Thirty‐four healthy subjects unexposed to COVID‐19 were used as controls. Results APLA were present in 7 of 122 (6%) CCP samples. One donor had anti‐β2‐glycoprotein 1(anti‐β2GP1) IgG, one had anti‐β2GP1 IgM and five had lupus anticoagulant (LAC) using silica clotting time (SCT), all in ‘late period’ donors. In the control group, one subject had anti‐β2GP1 IgG, two had LAC using dilute Russell viper venom time (dRVVT) and four had LAC SCT (both LAC SCT and LAC dRVVT in one subject). Conclusion The low prevalence of APLA in CCP donors reassures the safety of CCP administration to patients with severe COVID‐19.