Heterogeneity in Patient Characteristics and Differences in Treatment Across 4 Canadian Rheumatoid Arthritis Cohorts.

Objective: To compare clinical characteristics and treatment of patients with rheumatoid arthritis (RA) across 4 Canadian cohorts.

Methods: The 4 longitudinal cohorts included the following: the Canadian Early Arthritis Cohort (CATCH; n = 2878), Ontario Best Practices Research Initiative (OBRI; n = 3734), RHUMADATA (Quebec, n = 2890), and the Rheum4U Precision Health Registry (Calgary, Alberta, n = 709). Data were from cohort inception (range 1998-2016) to 2020. Clinical characteristics and drug treatments were summarized descriptively.

Results: In total, 10,211 patients with RA were included. The percentage of patients who entered the cohort with early RA (2 yrs of disease at enrollment) ranged from 29% (Rheum4U) to 100% (CATCH). Mean age (55 yrs), sex (74% female), and seropositivity (69%) were similar between cohorts. At the time of initial disease-modifying antirheumatic drug (DMARD) use, median Disease Activity Score in 28 joints (DAS28) varied, ranging from 2.99 (Rheum4U) to 5.19 (CATCH), but were more similar at the time of the first DMARD switch (range 3.57-5.03), first biologic (bDMARD) or targeted synthetic DMARD (tsDMARD) use (range 4.01-4.67), and second bDMARD or tsDMARD (range 3.71-4.39). The initial DMARD was most commonly methotrexate, either in monotherapy (32%, range 18-40%) or dual therapy (34%, range 29-42%). The first DMARD switch was to another DMARD monotherapy in 20% (range 10-32%), dual therapy in 49% (range 39-56%), and bDMARD or tsDMARD in 24% (range 15-28%). The first bDMARD was an anti-tumor necrosis factor in 79% (range 78-82%).

Conclusion: Canadian RA cohorts demonstrate some heterogeneity in treatment, which could reflect differences in inclusion criteria, calendar year, or regional differences. This project is a first step toward conducting harmonized analyses across Canadian RA cohorts.