Reduced joint count indices in the evaluation of rheumatoid arthritis.

Two types of summary measures of joint disease were evaluated in 2 controlled clinical trials in rheumatoid arthritis patients. One measure was based solely on the clinical/biologic judgment approach; the other combined this methodology with statistical approaches using reliability and factor analyses. "Signal joint" indices, summarizing disease activity in 2-5 key joints, were found to be insensitive to deterioriation of nonsignal joints. Therefore, they are not recommended as replacements for the complete articular survey in rheumatoid arthritis. A reduced version of the complete articular survey was found to be desirable based on its validity, reliability, accuracy, precision, and sensitivity to active drugs. Its sensitivity can be slightly higher or lower than that of the full joint survey.