COVID-19 testing 20% higher among patients with immune-mediated inflammatory disease
Patients with immune mediated inflammatory diseases are tested for COVID-19 at a 20% higher rate than the general population, according to data published in Arthritis Care & Research.
However, despite this higher rate of testing, the risk for SARS-CoV-2 infection was not significantly higher among most patients with IMIDs compared with their non-IMID peers.
“Despite multiple studies on the risk of COVID-19 infection and its complications in IMIDs, evidence from population-based studies is limited,” Lihi Eder, MD, PhD, of the University of Toronto Women’s College Research Institute, and colleagues wrote. “Observational studies reliant on self-report of infection status, hospital admissions, and targeted testing in selected populations have been reported but are prone to selection biases. Reported COVID-19 infection rates are functions of sociodemographic factors and comorbidities which influence the propensity of individuals to undergo SARS-CoV-2 testing.”
“Previous studies that have restricted their analysis to hospitalized patients, people tested for active infection, or people who volunteered to participate are most susceptible to collider bias as the relationships between any variables that relate to outcome will be distorted compared to among the general population,” they added. “Since it is challenging to identify all such potential confounders to mitigate this collider bias, accurate estimates of COVID-19 risk in IMIDs are best obtained from studies involving unselected population-based data and careful adjustment of factors affecting SARSCov-2 testing.”
To examine the incidence of, and factors linked with, COVID-19 testing and infection among patients with IMIDs, compared with those without IMIDs, Eder and colleagues conducted a population-based, matched cohort study of adults, aged 20 years and older, in Ontario, Canada, from January 2020 to December 2020. In all, the study included 493,499 patients with rheumatoid arthritis, psoriasis, psoriatic arthritis, ankylosing spondylitis, systemic autoimmune rheumatic diseases, multiple sclerosis, iritis, inflammatory bowel disease, polymyalgia rheumatica and vasculitis, as well as 2,466,946 from the general population.
The researchers obtained data through the Ontario Health Insurance Plan, a public, single-payer health system that covers hospital admissions, physician services and COVID-19 tests for all Ontario residents. Each included patient with an IMID was matched with five individuals without IMIDs based on socio-demographic factors. The researchers then estimated the incidence of COVID-19 testing and infection among the two groups. They also used multivariable logistic regressions to determine the odds of SARS-CoV-2 infection.
According to the researchers, patients with IMIDs were more likely to have at least one COVID-19 test, compared with those without IMIDs, at 27.4% versus 22.7%. However, the proportion of those who tested positive for COVID-19 was identical, at 0.9% in both groups. Overall, patients with IMIDs demonstrated 20% higher odds of being tested for COVID-19 (OR = 1.2; 95% CI, 1.19-1.21).
Meanwhile, the odds of SARS-CoV-2 infection varied across IMIDs groups. However, they were not significantly elevated for most patients compared with the general population. For example, the odds of SARS-CoV-2 infection was lower in patients with IBD and multiple sclerosis, and marginally higher in those with RA and iritis.
“Despite the fact that patients with IMIDs were more likely to be tested for SARS-COV2 than the population comparators, their risk of contracting the infection was similar to controls,” Eder told Healio Rheumatology. “It should be emphasized that this study did not evaluate the risk of being hospitalized to due COVID-19, which has been shown by our group and others to be higher in patients with IMIDs.”
“We also found that risk factors for infection are similar to those seen in the general population and include urban living, lower socioeconomic factors, multimorbidity and living in long-term care,” Eder added. “Overall, the study provides insights about the epidemiology of COVID-19 in patients with IMIDs prior to the vaccination rollout.”