Background/Purpose: The COVID-19 pandemic has caused over 3 million deaths. Having inflammatory arthritis (IA) and anti-rheumatic medications increase the risk of infections. Comorbidities, common in IA, have been associated with increased mortality with COVID-19. In the U.K, including Wales, governments advised vulnerable individuals including many patients with IA to self-isolate at home (shielding) by letters.

A small primary care cohort and the global rheumatology registry found an increased risk of severe disease and mortality in patients with rheumatic diseases (4-5). Comorbidities and a moderate to a high dose of glucocorticoids were associated with a higher risk of being hospitalised.

Using the complete COVID-19 test data for the entire nation of Wales, U.K, we compared the incidence and mortality of COVID-19 in patients with IA with controls for an entire nation with a 3 million population

Methods: All individuals who tested positive for COVID-19 from 1/3/20 to 12/05/21 formed the population. Primary care and hospital healthcare records were linked anonymously using a multiple encryption system by NHS Wales Informatics Service (6). Individuals with diagnosis codes for Rheumatoid Arthritis, Psoriatic Arthritis and Ankylosing Spondylitis comprised the IA patients, while those without these codes were the control population. Individuals who were under 18 years of age when tested for COVID-19 were excluded from the analysis.

The incidence rate of COVID-19 was assessed by Chi-square statistics. COX proportional hazard models were used to generate hazard ratios (HR) of death following COVID-19 for IA patients compared to controls. Univariable analysis informed the significant candidate variables (at p< 0.05 level of significance) to be added to the final model in a stepwise model. Analyses were conducted for 1^st (Mar-Jun 20) and 2^nd (Sep 20-May 21) waves as well as in between these periods.

Results: Over 3 million COVID-19 tests were conducted. The incidence rate of COVID-19 for patients with IA was 2,031/100,000, compared to 22,755/100,000 for those without IA (Chi-Square p=0.0001). Patients with IA were statistically significantly older and had more comorbidities.

The proportion of patients with IA admitted to hospital post-COVID test was statistically significantly higher compared to those without IA (1^st wave: difference 24.5%, 95% CI: 18.4-30.7). The proportion of patients deceased following COVID-19 was statistically significantly higher in IA patients during the first wave (difference 21.4, 95% CI: 15.7 to 27.4) and second wave (difference 10.9, 95% CI: 8.6 to 13.6) (Table 1).

Adjusted COX hazard models showed that being a shielded individual, advanced age, ever smoker, diabetes, previous history of serious infection requiring hospitalisation and glucocorticoids were associated with increased risk of death in IA patients compared to controls (Table 1). Being female was associated with a reduced risk of death.

Conclusion: Patients with IA have a lower risk of contracting COVID perhaps due to shielding. Mortality was significantly higher in IA patients compared to controls which was due to older age and had more comorbidities. The only IA related risk factor associated with higher mortality was corticosteroids.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/lower-incidence-of-covid-19-but-higher-mortality-in-patients-with-inflammatory-arthritis-compared-to-controls-in-wales-united-kingdom-a-population-epidemiological-study/