Comparative responsiveness of four elbow scoring instruments in patients with rheumatoid arthritis

Objective. This prospective study investigated the comparative responsivene ss to change of 4 different elbow scoring instruments: 2 Hospital for Speci al Surgery elbow assessment scales, the Mayo Clinic Elbow Performance Index , and the Elbow Functional Assessment (EFA) Scale. Methods. A group of patients with rheumatoid arthritis (RA) (median age 60 yrs) undergoing either elbow arthroplasty (22 elbows) or synovectomy with r adial head excision (3 elbows) were evaluated both before and after surgery (median 7 mo postoperatively). Changes in the scores obtained using the sc ales under study were calculated and analyzed. The patient's opinion of glo bal perceived effect or the intervention was used as an external criterion to classify them as "improved" or "non-changed." Responsiveness was evaluat ed with 3 different statistical approaches: using paired t statistics (pre and postsurgery scores), effect size statistics (standardized response mean , effect size, and responsiveness ratios), and receiver operator characteri stic curves. Minimal clinically important difference was estimated using pa tient satisfaction as the external criterion. Results. Each of the elbow rating measures under study proved to be respons ive to change when evaluating patients with RA undergoing elbow arthroplast y or synovectomy. The EFA scale had the highest power to detect a clinicall y meaningful difference and had the best discriminative ability to distingu ish improved from no-change patients, as shown by all responsiveness statis tics applied. Conclusion. Using the EFA scale requires smaller sample sizes to achieve a fixed level of statistical power than the other scales we studied.