Osteoarthritis antirheumatic drug trials. I. Effects of standardization procedures on observer dependent outcome measures.

We designed a study to assess the effects of standardization procedures on reducing interobserver variability for outcome measures given in the current Food and Drug Administration and European League Against Rheumatism guidelines and others selected from the rheumatology literature. Over 2 days, 6 rheumatologists independently examined 6 patients with osteoarthritis (OA) in predetermined order before and after standardizing their examination techniques. An important and beneficial effect of the standardization procedure was observed on the majority of outcome variables. Such reductions in observer variability have the potential to diminish sample size requirements for OA antirheumatic drug studies.