Prevalence of COVID‐19 and seroprevalence to SARS‐CoV‐2 in a rheumatologic patient population from a tertiary referral clinic in Israel

Eviatar, Tali; Elalouf, Ofir; Furer, Victoria; Goldstein‐Lahat, Yael; Paran, Yael; Pel, Sara; Nevo, Sharon; Zisapel, Michael; Alcalay, Yifat; Elkayam, Ori

BACKGROUND: It is unclear if the prevalence of COVID‐19 in rheumatologic patients is similar to that of the general population. There are no reports of seroprevalence of SARS‐CoV‐2 in these patients. AIMS: To investigate prevalence of COVID‐19 cases and seroprevalence among rheumatologic patients and the risk factors for infection. METHODS: A cross‐sectional study in a rheumatologic population. An online questionnaire was sent on 31 April 2020. Blood samples from 20% sample of patients were drawn for SARS‐CoV‐2 antibodies. Patients were divided based on autoimmune (AI) diagnosis. Prevalence of COVID‐19 by nasopharyngeal swab and by serology (seroprevalence) was compared to national data. Risk factors for infection of SARS‐CoV‐2 were assessed. RESULTS: The study group included 1204 patients, 74.5% had an AI diagnosis. The prevalence of COVID‐19 was 0.16% in the rheumatologic patient population and 0.22% in the AI group, which was not different from prevalence in Israel on 4 May 2020 (0.18%, P = 0.912 and P = 0.759 respectively). Serologic tests were performed in 242 patients, of which five were found positive pointing to a seroprevalence of 2.07%. Exposure to a known COVID‐19 patient was the only significant risk factor for being positive by swab or by serology. AI diagnosis, immunosuppression, corticosteroid, hydroxychloroquine did not influence the risk. CONCLUSIONS: The prevalence of COVID‐19 in a population of rheumatologic patients was similar to that of the general population. Mild/asymptomatic cases may be prevalent according to serologic tests. The major risk factor for infection is exposure to a known case of COVID‐19, and immunosuppression did not play a role in the risk of infection.