Frequency and clinical correlates of antiphospholipid antibodies arising in patients with SARS-CoV-2 infection: findings from a multicentre study on 122 cases.

Objectives COVID-19 features include disseminated intravascular coagulation and thrombotic microangiopathy indicating a hypercoagulable state. We aimed to investigate antiphospholipid antibodies (aPL) prevalence and clinical relationships in a large cohort of COVID-19 patients. Methods We analysed the prevalence and titres of serum aPL in 122 patients with COVID-19 and 157 with primary antiphospholipid syndrome (PAPS) and 91 with other autoimmune rheumatic diseases (oARD) for comparison. IgG/IgM anticardiolipin (aCL) and IgG/IgM anti-beta2glycoprotein I (beta 2GPI) were assayed using homemade ELISA, IgA aCL and anti-beta 2GPI by commercial ELISA kits and lupus anticoagulant (LAC) by multiple coagulation tests following updated international guidelines. Results Prevalence of IgG and IgM aCL and of IgG and IgM anti-beta 2GPI across COVID-19 patients were 13.4%, 2.7%, 6.3% and 7.1%, being significantly lower than in PAPS (p<0.0001 for all). Frequency of IgG aCL and IgM anti-beta 2GPI was comparable to oARD (13.4% vs. 13.2% and 7.1% vs. 11%, respectively), while IgG anti-beta 2GPI and IgM aCL were lower (p<0.01). IgA aCL and IgA anti-beta 2GPI were retrieved in 1.7% and 3.3% of COVID-19 patients, respectively. Positive LAC was observed in 22.2% COVID-19 vs. 54.1% of PAPS (p<0.0001) and 14.6% of oARD (p=0.21). Venous or arterial thromboses occurred in 18/46 (39.1%) COVID-19 patients and were not associated with positive aPL (p=0.09). Conclusions Thrombosis is a frequent manifestation during COVID-19 infection. However, prevalence and titres of aPL antibodies or LAC were neither consistently increased nor associated with thrombosis when measured at a single timepoint, therefore not representing a suitable screening tool in the acute stage of disease.