Abstract
Objectives: To investigate whether patients with Rheumatoid Arthritis enrolled in randomized controlled trials (RCTs) and observational studies may differ in terms of characteristics that could modify treatment effects leading to effectiveness gap.
Methods: We conducted systematic literature reviews to identify RCTs with RA treated with rituximab. We compared this to data from the registry of RA cases on rituximab. We further used meta-regression analyses to assess the differences in DAS28 between RCTs and observational studies (The KRRD) by including the study design as a dichotomous covariate assessment of whether the baseline characteristics changed over time.
Results: Compared to Observational studies, the average DAS28 for RCTs are higher by 2.78 to 4.06 at baseline and 0.65 to 2.99 after baseline (P<0.001).
Furthermore, ESR and CRP declined over time in RCT patients, but not in patients participating in the registry. Overall, the patients in the registry were older than the RCT.
Conclusion: we found important differences between RA patients included in RCTs as compared with observational studies; in particular, patients with better prognostic factors were included in the RCTs, leading to a potential overestimation of the treatment effect.