Sensitivity to change of the Health Assessment Questionnaire (HAQ) and other clinical and health status measures in rheumatoid arthritis results of short‐term clinical trials and observational studies versus long‐term observational studies

To obtain evidence concerning short-term and long-term efficacy of clinical and health status measures in rheumatoid arthritis (RA), we conducted two observational studies--a 6-month study of 233 patients receiving methotrexate and a 10-year study of 157 patients receiving multiple treatments in a rheumatic disease clinic. Results of the 6-month study yielded effect sizes for treatment similar to the meta-analyses reported by Felson corrected et al. (Arthritis Rheum 33:1449-1461, 1990) and the controlled trials of methotrexate reported by Weinblatt et al. (Arthritis Rheum 33:330-338, 1990), suggesting that observational studies provide valid measurements of treatment effect. The effect size for the Health Assessment Questionnaire (HAQ) was 0.5. By contrast, the 10-year study suggested that standard clinical variables changed little and were not useful in assessing RA outcome, while the effect size of the HAQ was -2.39. These data continue to underscore the differences between short-term trials and the long-term outcome of RA, and suggest an important place for the HAQ or similar instruments in all phases of RA evaluation and assessment.