Background: Prior studies have shown that in the real-world setting, rheumatoid arthritis (RA) patients have lower disease activity than those studied in clinical trials. However, randomized controlled trials for biologics continue to mainly recruit patients with severe disease.
Objectives: To assess the implications of this practice, our study investigates the proportion of patients achieving remission (DAS28-ESR ≤ 2.6), in RA patients with moderate disease activity and severe disease activity, at 12 months post starting their first biologic, and identifies baseline predictors of biologic response.
Methods: This study included RA patients who have never been treated with a biologic and initiated their first biologic while enrolled in the Ontario Best Practices Research Initiative (OBRI) registry, between 2008 and 2019. Patients selected had either moderate RA (DAS28 ≥ 3.2 to ≤ 5.1) or severe RA (DAS28 > 5.1). Comparisons were made between the moderate and severe disease groups using the student’s t-test for continuous variables, and the chi-square test for categorical variables. Multivariable logistic regression was used to test potential predictors of remission. Backward stepwise model selection was applied to select variables with p-value ≤0.10. Multiple imputation (MCMC method; n=20) was used to impute missing data.
Results: Overall, 641 patients initiated their first biologic, 483 had follow up data at 12 months (moderate disease activity=264; severe disease activity=219). In the moderate group, the mean age (SD) was 55.7 (13.1) and 80% were female. In the severe group, mean age (SD) was 58.4 (12.3) and 81% were female. At time of biologic initiation, the mean DAS28 for the moderate group was 4.1 (0.5), and 6.0 (0.6) for the severe group. After 12 months of starting a biologic, the proportion of patients achieving remission was 50% in the moderate group, and 23% in the severe group (p<0.0001). In contrast, the proportion of patients achieving significant clinical change from baseline (improvement in DAS28 ≥ 1.2) was 78% in the severe group, compared to 66% in the moderate group (p=0.0049). More specifically, the absolute improvement in DAS28 after 12 months was higher in the severe group at 2.2 (1.5), compared to a change of 1.4 (1.3) in the moderate group (p<0.0001). Negative predictors of remission include female gender (odds ratio (OR), 0.57, 95% confidence interval (CI), 0.33-0.97; p=0.039), and higher HAQ-DI score (OR 0.49, 95% CI 0.36-0.68; p<0.001). In turn, moderate disease at time of biologic initiation (OR 2.38, 95% CI 1.50-3.79; p=0.0390) was identified as a positive predictor of remission.
Conclusion: This prospective cohort study found RA patients with moderate disease activity are more likely to reach targeted states (remission and low disease activity), whereas severe patients have greater absolute improvements in DAS28 and HAQ-DI but are less likely to achieve remission. Moderate disease is a positive predictor for remission, whereas female gender and a higher HAQ-DI score are negative predictors.
Disclosure of Interests: Nancy Guo: None declared, Xiuying Li: None declared, Mohammad Movahedi: None declared, Angela Cesta: None declared, Claire Bombardier Grant/research support from: OBRI was funded by peer reviewed grants from CIHR (Canadian Institute for Health Research), Ontario Ministry of Health and Long-Term Care (MOHLTC), Canadian Arthritis Network (CAN) and unrestricted grants from: Abbvie, Amgen, Aurora, Bristol-Meyers Squibb, Celgene, Hospira, Janssen, Lilly, Medexus, Merck, Novartis, Pfizer, Roche, Sanofi, & UCB.
Acknowledgment: : Dr. Bombardier held a Canada Research Chair in Knowledge Transfer for Musculoskeletal Care and a Pfizer Research Chair in Rheumatology
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