['To compare the EULAR and SDAI50 response measures (RMs) and their impact on future response to treatment in patients with early rheumatoid arthritis (ERA).', 'Biologic naïve ERA patients from the Canadian early ArThritis CoHort (CATCH) with complete data at baseline, 3 and 6 months were evaluated. Kappa statistics were used to evaluate the agreement between the EULAR (moderate or good response) and SDAI50 RMs. The RMs at 3 months were also compared for their ability to predict low disease activity state (LDAS) or remission (REM) at 6 months.', 'A total of 1124 patients were evaluated. Of those, 215 (30%) and 294 (45%) patients failed to achieve a EULAR and SDAI50 RMs respectively. There was a good agreement between EULAR and SDAI50 RMs with a Kappa of 0.59 (95% CI 0.53- 0.66). Throughout the range of disease activity, the SDAI50 response was shown to be more stringent than the EULAR response. Multivariable linear regression analysis demonstrated that both RMs at 3 months were associated with LDAS or REM at 6 months and SDAI50 had a more significant impact on the this outcome compared to the EULAR response.'] Is sDAI 50 more stringent than EULAR response measure and a better predictor of low disease state/remission in early rheumatoid arthritis in the first 6 months : Results from an Early Arthritis Cohort?