Significant changes in Ritchie scores.

A study was designed to establish the reliability of assessing joint tenderness in rheumatoid arthritis. Reliability both within and between observers was measured and the 95% confidence intervals (CI) for a change in score calculated. Forty-two patients were assessed by two metrologists over a 14-week period using three subjects per week. Results showed close agreement within and between metrologists. The 95% CI for repeat measures by the same metrologist was +/- 8.5 and +/- 12 by a different metrologist. Taking a change of 5 in the score as clinically significant, the 95% CI for a clinically significant change would be +/- 14 with one observer and +/- 17 when a different observer repeated the assessment. It is recommended that other centres should establish their own CI for a change in scores when undertaking clinical trials.