Reliability, validity, and sensitivity to change of the Cochin hand functional disability scale in hand osteoarthritis

Objective: To assess the reliability, validity and sensitivity to change of the Cochin hand functional scale in hand osteoarthritis (OA).

Background: The Cochin hand functional disability scale has been validated in rheumatoid arthritis.

Design: Patients with hand OA according to Altman's criteria were included. Impairment outcome measures (VAS of pain, hand score of tenderness, clinical hand score of impairment, Kallman's radiographic scale), functional disability measures [Cochin scale, Revel's functional index (RFI), Dreiser's functional index (DFI)] and patients' perceived handicap (VAS) were recorded twice, at baseline and at a 6-month follow-up visit. Interobserver reliability was assessed using the intraclass correlation coefficient (ICC) and the Bland and Altman method. Construct (convergent and divergent) validity was investigated using the Spearman rank correlation coefficient and a factor analysis was performed. Sensitivity to change was assessed using the effect size (ES) and the standardized response mean (SRM), and the non-parametric Spearman rank correlation coefficient (r) was used to assess the correlation between quantitative variable changes and patient's overall opinion.

Results: 89 patients (8 males, mean age 63 years) were included. Interobserver reliability was excellent (ICC=0.96). The Bland and Altman method showed no systematic trend. Correlations of the Cochin scale score with RFI (r=0.86), DFI (r=0.87), VAS of handicap (r=0.67), VAS of pain (r=0.54), tenderness (r=0.51), clinical impairment (r=0.32), and Kallman's radiographic scale (r=0.13) indicated a good construct validity. Factor analysis extracted four main factors, accounting for 65% of the total variance. 51 patients were evaluated at the 6-month visit. The Cochin scale score had worsened with SRM and ES values of -0.26 and -0.17 respectively. Changes in the score had one of the highest correlation (r=0.47) with the patient's overall opinion.

Conclusion: The Cochin hand functional disability scale which was first developed to assess the rheumatoid hand can be used to evaluate functional disability in hand OA.