To explore the ability of six outcome measures to capture clinically important changes in patients with rheumatic diseases undergoing hand surgery and to study predictors of changes in activity performance in different patient and surgery strata.
A total of 172 patients (median age 59 years, disease duration 18 years) were stratified into subgroups: diagnosis, age, general function, type of surgery. Performance of daily activities and satisfaction were assessed by the Canadian Occupational Performance Measure (COPM). Clinically important improvement was defined as a two-step improvement in COPM. Hand function was assessed by reference to grip strength (Grippit), pinch strength (pinch gauge), hand pain (visual analogue scale) and grip ability (Grip Ability Test). Responsiveness was calculated as effect size (ES) at 6-month follow-up compared with baseline.
Clinically important improvement was reached by 25-69% depending on outcome measure and type of surgery. Improvement was smaller in patients with multiple simultaneous procedures. Regardless of diagnosis, age, general function and type of surgery, patients improved significantly in all measures, with the largest changes in COPM(performance) and COPM(satisfaction) (ES 0.7-1.9). The ES of pain ranged from 0.2 to 0.7, Grippit from 0.1 to 0.5 and pinch gauge from 0.4 to 0.8. Hand pain was the only significant predictor of clinically important improvement of COPM(performance): odds ratio 0.71, 95% CI 0.51, 0.98 (P = 0.041).
COPM was the most sensitive instrument to capture clinically important improvement, and hand pain was a significant predictor of improvement, irrespective of diagnosis, age, general functional level and type of surgery.