To develop a set of disease activity measures for use in rheumatoid arthritis (RA) clinical trials, as well as to recommend specific methods for assessing each outcome measure. This is not intended to be a restrictive list, but rather, a core set of measures that should be included in all trials.
We evaluated disease activity measures commonly used in RA trials, to determine which measures best met each of 5 types of validity: construct, face, content, criterion, and discriminant. The evaluation consisted of an initial structured review of the literature on the validity of measures, with an analysis of data obtained from clinical trials to fill in gaps in this literature. A committee of experts in clinical trials, health services research, and biostatistics reviewed the validity data. A nominal group process method was used to reach consensus on a core set of disease activity measures. This set was then reviewed and finalized at an international conference on outcome measures for RA clinical trials. The committee also selected specific ways to assess each outcome.
The core set of disease activity measures consists of a tender joint count, swollen joint count, patient's assessment of pain, patient's and physician's global assessments of disease activity, patient's assessment of physical function, and laboratory evaluation of 1 acute-phase reactant. Together, these measures sample the broad range of improvement in RA (have content validity), and all are at least moderately sensitive to change (have discriminant validity). Many of them predict other important long-term outcomes in RA, including physical disability, radiographic damage, and death. Other disease activity measures frequently used in clinical trials were not chosen for any one of several reasons, including insensitivity to change or duplication of information provided by one of the core measures (e.g., tender joint score and tender joint count). The committee also proposes specific ways of measuring each outcome.
We propose a core set of outcome measures for RA clinical trials. We hope this will decrease the number of outcomes assessed and standardize outcomes assessments. Further, we hope that these measures will be found useful in long-term studies.