Seroprevalence of SARS-CoV-2 antibodies in patients with autoimmune inflammatory rheumatic diseases.

Objectives: To assess the prevalence of anti-SARS-CoV-2 antibodies in autoimmune inflammatory rheumatic disease (AIIRD) patients, and to define clinical factors associated with seropositivity.

Methods: A cross sectional study was conducted at a tertiary rheumatology department in Israel. Consecutive patients completed a questionnaire and were tested for SARS-CoV-2 anti-nucleoprotein IgG (N-IgG). If this was positive, an anti-S1/S2 spike IgG (S-IgG) test was done. If both were positive, the patient was considered seropositive. Seropositive patients were retested after 3 months.

Results: The study included 572 AIIRD patients. Thirty patients were found seropositive, for a seroprevalence of 5.24%. The seropositive rate was significantly lower for patients treated with immunosuppressive medications (3.55%, p≤0.01), and specifically for patients treated with biologic disease-modifying anti-rheumatic drugs (bDMARDs) (2.7%, p≤0.05). These associations remained significant in the multivariate regressions adjusting for age, sex and exposure to a known COVID-19 patient. A second serology test 3 months later was collected in 21 of the 30 seropositive patients. In a mean±standard deviation (SD) of 166.63±40.76 days between PCR and second serology, 85% were still positive for N-IgG, and 100% were still positive for S-IgG, with a higher mean±SD titre compared to the first S-IgG (166.77±108.77 vs. 132.44±91.18, respectively, p≤0.05).

Conclusions: Humoral response to SARS-CoV-2 in AIIRD patients may be affected be immunosuppressive treatment, especially bDMARDs. In patients with AIIRD, titres of SARS-CoV-2 IgG antibodies, especially N-IgG antibodies, fade with time, while S-IgG antibodies persist.