Trials in rheumatoid arthritis: choosing the right outcome measures-comment on the article by Felson et al

摘要

Felson et al make a good case for choosing continuous, rather than dichotomous, variables as the primary outcome measures in randomised controlled trials in rheumatoid arthritis; however, outcome measures also need to be meaningful to the clinical community. In TICORA we chose two "co-primary" end-points: first, we employed the mean change in disease activity score (DAS) because this was the most sensitive outcome measure available at the time; we also used the achievement of a "good" response according to EULAR criteria because we believed that differences in response rates would be more readily understood. Interestingly, our understanding of the clinical relevance of the outcome measures has been borne out: the results of the trial are (almost) never quoted as showing that the mean fall in DAS was 1.6 units (95% confidence interval, 1.1 to 2.1) greater in the intensive arm-commentators almost invariably refer instead to the higher response rates. Consequently, I would urge some caution in the clinical trials community not to rely on sensitive (but intuitively difficult to understand) outcome measures to the exclusion of response rates. This is acknowledged by Felson et al when they recognise that such measures can be secondary outcome measures but it may still be important that some trials (depending on their purpose) are large enough to be able to detect clinically significant differences in response rates.