Reliability, validity, and responsiveness of the modified Kapandji index for assessment of functional mobility of the rheumatoid hand

Objective: To determine the reliability, validity, and responsiveness of the modified Kapandji index (MKI). Design: Prospective study. A cohort of patients planned for surgery of the wrist and/or fingers was evaluated within 48 hours before surgery and at least 6 months after surgery. Setting: Patients were in hospitalized or private care in France. Participants: Patients with rheumatoid arthritis according to criteria of the American College of Rheumatology. Forty-two patients (36 women; mean age, 57.5y; range, 22-80y) were included in the reliability study. Fifty patients (42 women; mean age, 54.18y; range, 19-77y) were included in the validity study. Interventions: Not applicable. Main Outcome Measures: Clinical outcome measures included the MKI, the overall mobility score of the wrist and fingers, the finger mobility score, a visual analog scale (VAS) of pain in the hands and wrists, morning stiffness duration, total score of tenderness, total score of swelling, grip and pinch strength, the Hand Functional Index (HFI), and the Cochin rheumatoid hand disability scale. Reliability was studied with the intraclass correlation coefficient (ICC) and the Bland and Altman method. Convergent and divergent validity were assessed with the Spearman correlation coefficient. Responsiveness was assessed by the paired t test, the effect size, and the standardized response mean (SRM). Results: Interobserver reliability was good with an ICC of .90, and the Bland and Altman analysis showed homogeneous distribution of the differences, with no systematic trend. The MKI correlated well with the other mobility measures (HFI, the finger mobility score measured with the finger goniometer), indicating a good convergent validity, and the expected divergent validity with the other outcome measures (grip and pinch strength, total score of swelling, total score of Ritchie Articular Index, Cochin scale, VAS of pain) was observed. The 50 patients in the validity study were evaluated twice, before and after surgery, at a mean interval standard deviation of 7.16 +/- 2.10 months (range, 6-15mo). Thirty-six patients (72%) were very satisfied or satisfied with the results of surgery, 7 (14%) were not satisfied or dissatisfied, and 7 (14%) were dissatisfied or very dissatisfied. The SRM and effect size values of the MKI were -.19 and -.10, respectively. Individual changes in the score had the best correlation (r(s)=.51) with overall patient satisfaction. Conclusions: The MKI has excellent validity and reliability. Individual changes in the score are clinically relevant. This index can be used in clinical practice and in therapeutic trials; it needs further study concerning its use for hand surgery.