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.
To investigate prevalence of COVID-19 cases and seroprevalence among rheumatologic patients and the risk factors for infection.
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.
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.
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.