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

OBJECTIVE: This prospective study investigated the comparative responsiveness to change of 4 different elbow scoring instruments: 2 Hospital for Special 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 radial head excision (3 elbows) were evaluated both before and after surgery (median 7 mo postoperatively). Changes in the scores obtained using the scales under study were calculated and analyzed. The patient's opinion of global perceived effect of the intervention was used as an external criterion to classify them as "improved" or "non-changed." Responsiveness was evaluated 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 characteristic curves. Minimal clinically important difference was estimated using patient satisfaction as the external criterion.
RESULTS: Each of the elbow rating measures under study proved to be responsive to change when evaluating patients with RA undergoing elbow arthroplasty or synovectomy. The EFA scale had the highest power to detect a clinically meaningful difference and had the best discriminative ability to distinguish improved from no-change patients, as shown by all responsiveness statistics applied.
CONCLUSION: Using the EFA scale requires smaller sample sizes to achieve a fixed level of statistical power than the other scales we studied.