Psychometric Properties of the Dance Functional Outcome Survey (DFOS): Reliability, Validity and Responsiveness.

Study Design Prospective cohort study. Background There are no outcomes measures that focus on the unique functional requirements of dancers. Objectives To evaluate test-retest reliability, internal consistency, construct validity, sensitivity and responsiveness of the Dance Functional Outcome Survey (DFOS) in professional and pre-professional adult dancers. Methods We examined test-retest reliability of DFOS in 198 healthy and injured dancers within 2-wks using intraclass correlation coefficients (ICC2,1 ). In a sample of 725 healthy and injured dancers, we examined: i) construct validity comparing DFOS to SF-36 using Pearson correlations, ii) exploratory factor analysis and internal consistency; and iii) sensitivity by generating receiver operating characteristic curves and determining area under the curve. In a subgroup of 47 injured dancers, we determined internal responsiveness across four time-points using repeated measures ANOVA (p<0.05). Injured scores were analyzed for floor and ceiling effects. Results DFOS demonstrated high test-retest reliability (ICC≥0.93). Single-factor loading in exploratory factor analysis supported uni-dimensionality of the scale with high internal consistency (α=0.96). DFOS-total, ADL and Technique scores had strong construct validity compared with SF-36 PCS (r≥0.77). We found excellent sensitivity with high area under the curve values (AUC≥0.91). There were significant differences across time for DFOS scores (p<0.001), demonstrating responsiveness to change. There were no floor or ceiling effects exceeding 15%. Conclusion DFOS demonstrates acceptable psychometric performance as an outcome and screening measure for dancers. DFOS is a useful tool to monitor both healthy state and functional limitation following lower extremity or low back injury in adult ballet and modern dancers. J Orthop Sports Phys Ther, Epub 27 Jul 2018. doi:10.2519/jospt.2019.8247.