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Understanding COVID-19 risk in patients with immune mediated inflammatory diseases: a population-based analysis of SARS-CoV-2 testing

Eder L, Croxford R, Drucker AM, Mendel A, Kuriya B, Touma Z, Johnson SR, Cook R, Bernatsky S, Haroon N, Widdifield J. Arthritis Care Res (Hoboken). 2021; Sep 6 [Epub ahead of print]. DOI:

Objective — To investigate the incidence of and factors associated with SARS-CoV-2 testing and infection in immune mediated inflammatory diseases (IMIDs) versus matched non-IMIDs comparators from the general population.

Methods — We conducted a population-based, matched cohort study among adult residents from Ontario, Canada, from January to December 2020. We created cohorts for the following IMIDs: rheumatoid arthritis (RA), psoriasis, psoriatic arthritis, ankylosing spondylitis, systemic autoimmune rheumatic diseases, multiple sclerosis (MS), iritis, inflammatory bowel disease (IBD), polymyalgia rheumatica and vasculitis. Each patient was matched with five patients without IMIDs based on socio-demographic factors. We estimated the incidence of SARS-CoV-2 testing and infection in IMIDs and non-IMIDs patients. Multivariable logistic regressions assessed odds of SARS-CoV-2 infection.

Results — We studied 493,499 patients with IMIDs and 2,466,946 patients without IMIDs. Patients with IMIDs were more likely to have at least one SARS-CoV-2 test, versus patients without IMIDs (27.4% vs. 22.7%), but the proportion testing positive for SARS-CoV-2 was identical (0.9% in both groups). Overall, IMIDs patients had 20% higher odds of being tested for SARS-CoV-2 (odds ratio (OR) 1.20, 95% CI 1.19, 1.21). The odds of SARS-CoV-2 infection varied across IMIDs groups but was not significantly elevated for most IMID groups compared with non-IMIDs. The odds of SARS-CoV-2 infection was lower in IBD and MS and marginally higher in RA and iritis.

Conclusions — Patients across all IMIDs were more likely to be tested for SARS-CoV-2 versus those without IMIDs. The risk of SARS-CoV-2 infection varied across disease sub-groups.

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