Heterogeneity in patient characteristics and differences in treatment across four Canadian rheumatoid arthritis cohorts.

Objective To compare clinical characteristics and treatment of patients with rheumatoid arthritis (RA) across 4 Canadian cohorts. Methods The four longitudinal cohorts included: 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, n=709). Data were from cohort inception (range 1998-2016) to 2020. Clinical characteristics and drug treatments were summarized descriptively. Results 10,211 patients with RA were included. The percentage of patients who entered the cohort with early RA ( ≤ 2 years of disease at enrolment) ranged from 29% (Rheum4U) to 100% (CATCH). Mean age (55 years), sex (74% female) and seropositivity (69%) were similar between cohorts. At the time of initial disease modifying anti-rheumatic drug (DMARD) use, median disease activity scores (DAS-28) 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 or targeted synthetic DMARD (bDAMRD, tsDMARD) use (range:4.01-4.67) and second bDAMRD 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-TNF in 79% (range:78%-85%). 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 towards conducting harmonized analyses across Canadian RA cohorts.