Differences in the Modified Disablement in the Physically Active Scale in Those With and Without Chronic Ankle Instability

Context: The modified Disablement in the Physically Active scale (mDPA) has become a commonly utilized patient-reported outcome instrument for physically active patients. However, the factor structure of this instrument has not been verified in individuals with chronic ankle instability (CAI). Furthermore, additional evidence examining the mDPA in individuals with CAI is warranted. Objective: The purpose of this study was to verify the factor structure of the mDPA and compare the physical summary component (PSC) and mental summary component (MSC) in those with and without CAI. Design: Cross-sectional. Setting: Laboratory. Participants: A total of 118 CAI and 81 healthy controls from a convenience sample participated. Intervention: Not applicable. Main Outcome Measures: All subjects completed the 16-item mDPA that included the PSC and MSC; higher scores represent greater disablement. To examine the model fit of the mDPA, a single-factor and 2-factor (PSC and MSC) structures were tested. Group differences were examined with independent t tests (P <= .05) and Hedges' g effect sizes (ESs). Results: Model fit indices showed the 2-factor structure to possess adequate fit to the data, chi(2)(101) = 275.58, P < .001, comparative-fit index = .91, root mean square error of approximation = .09 (95% confidence interval [CI], .08-.11), and standardized root mean square residual = .06. All items loaded significantly and in expected directions on respective subscales (lambda range = .59-.87, all Ps < .001). The CAI group reported greater disablement as indicated from PSC (CAI: 11.45 [8.30] and healthy: 0.62 [1.80], P < .001, ES =1.67; 95% CI, 1.33-1.99) and MSC (CAI: 1.75 [2.58] and healthy: 0.58 [1.46], P < .001, ES = 0.53; 95% CI, 0.24-0.82) scores. Conclusions: The 2-factor structure of the mDPA was verified. Individuals with CAI reported greater disablement on the PSC compared with healthy controls. The moderate ES on the MSC between groups warrants further investigation. Overall, these results indicate the mDPA is a generic patient-reported outcome instrument that can be utilized with individuals who have CAI.