Testing and Risk of COVID-19 in Patients with Immune Mediated Inflammatory Disease

September 9, 2021
Giuliana Grossi

Investigators analyze the differences between SARS-CoV-2 testing and risk of infection.

Despite 20% higher rates of SARS-CoV-2 testing among patients with immune mediated inflammatory diseases (IMIDs), the risk of an actual infection was not significantly higher for most immune mediated inflammatory disease groups compared with those who don’t have the disease.

The aim of the study, conducted by a team led by Lihi Eder, MD, PhD, of Women’s College Research Institute, University of Toronto, was to investigate the incidence of and factors associated with SARS-CoV-2 testing and infection in immune mediated inflammatory diseases versus matched non-IMIDs comparators from the general population.

Within the immune mediated inflammatory disease groups, SARS-CoV-2 risk varied. Inflammatory bowel disease and multiple sclerosis showed to be lower in risk while rheumatoid arthritis and iritis were of higher risk across the subgroups.

The highest risks of SARS-CoV-2 infection were linked to urban living, multimorbidity, lower socioeconomic status, and residing in a long-term care facility.

The Study

In the population-based, matched cohort study, investigators assessed SARS-CoV-2 testing and infection from January 2020 to December 2020 using Ontario health administrative data. A total of 493,499 patients with immune mediated inflammatory disease were included and compared with a control group of 2,466,946 patients without the disease.

Patients were assembled into 10 cohorts of immune mediated inflammatory diseases including rheumatoid arthritis, psoriasis, psoriatic arthritis, ankylosing spondylitis, systemic autoimmune rheumatic diseases, multiple sclerosis, iritis, inflammatory bowel disease, polymyalgia rheumatica, and vasculitis.

Each immune mediated inflammatory disease patient was matched with 5 non-IMID patients based on age range, sex, region of residence, and if they’re residing in a long term care facility.

Information on SARS-CoV-2 testing was available through the Ontario Laboratory Information System, which captures approximately 88% of all laboratory identified SARS-CoV-2 cases reported by the province during the time period of the study. Each subject was identified to have had at least 1 test within the time period.

Testing & Results

Among the immune mediated inflammatory disease patients, the mean age was 58.3 years. 60.7% were females. 90.4% belonged to a single cohort category while the remaining patients belonged to 2 or more. 91.3% lived in urban areas while a small minority lived in a long term care facility (1.4%).

Testing rates were significantly higher across each immune mediated inflammatory disease group compared with their respective matched comparators. Testing was highest in patients with vasculitis, followed by inflammatory bowel disease and systemic autoimmune rheumatic diseases.

Patients with immune mediated inflammatory diseases were found to be 29% more likely to undergo SARS-CoV-2 testing. This association remained significant in the multivariable analysis.

The factor that was most strongly associated with SARS-CoV-2 testing among patients with immune mediated inflammatory diseases was residing in a long term care facility.

Of all patients with immune mediated inflammatory diseases, 0.9% (n = 4541), tested positive for SARS-CoV-2. In the control group 0.9% (n = 22,157) also tested positive.

The study concluded that while the testing rates of patients with immune mediated inflammatory diseases are higher, there’s no significant difference in the actual rate of infection between the patients who have an immune mediated inflammatory disease and the patients who don’t.

The study, "Understanding COVID-19 Risk in Patients with Immune Mediated Inflammatory Diseases: A Population-based analysis of SARS-CoV-2 Testing" was published in Arthritis Care & Research.


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