The importance of reporting disease activity states in rheumatoid arthritis clinical trials.

OBJECTIVE: To compare the value of reporting treatment effects in rheumatoid arthritis (RA) as relative change from baseline (e.g., American College of Rheumatology [ACR] responder status) with the value of evaluating absolute disease activity states (e.g., remission). METHODS: We pooled data from several recent RA clinical trials and evaluated patients who had completed a 1-year treatment period (n = 629). We compared levels of functional impairment and radiographic progression among patients meeting the ACR 50% or 70% improvement criteria (ACR50 and ACR70 responders, respectively) who attained remission of disease, low disease activity, or moderate disease activity after 1 year, as assessed by the Simplified Disease Activity Index and the Disease Activity Score in 28 joints. RESULTS: Within the ACR50 and ACR70 responder groups, functional disability and radiographic progression were lowest in patients who had attained disease remission at 1 year, compared with those who had attained low or moderate disease activity. When patients attained the same disease activity category, physical function and radiographic progression did not differ significantly with different response states. CONCLUSION: Functional and radiographic outcomes are different in patients depending on the disease activity category they attain, even if the same level of response (change from baseline) is achieved. Among patients who attain the same disease activity category, the degree of response they experience does not seem to matter. Assessing actual disease activity as well as disease activity states should constitute an integral part of clinical trial data reporting.