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

Abstract

There are no outcomes measures that focus on the unique functional requirements of dancers. To evaluate test-retest reliability, internal consistency, construct validity, sensitivity, and responsiveness of the Dance Functional Outcome Survey (DFOS) in professional and preprofessional adult dancers. This prospective cohort study examined test-retest reliability of the DFOS in 198 healthy and injured dancers over 2 weeks, using intraclass correlation coefficients (ICC2,1). In a sample of 725 healthy and injured dancers, the following were examined: (1) construct validity, by comparing the DFOS to the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36) using Pearson correlations; (2) exploratory factor analysis and internal consistency; and (3) sensitivity, by generating receiver operating characteristic curves and determining area under the curve (AUC). In a subgroup of 47 injured dancers, we determined internal responsiveness across 4 time points using repeated-measures analysis of variance (P<.05). Injured dancers' scores were analyzed for floor and ceiling effects. The DFOS demonstrated high test-retest reliability (ICC≥0.93). Single-factor loading in exploratory factor analysis supported unidimensionality of the scale, with high internal consistency (α = .96). The DFOS total score and activities-of-daily-living (ADL) and dance technique subscores had strong construct validity compared with scores on the SF-36 physical component summary (r≥0.77). This study found excellent sensitivity, with high AUC values (AUC≥0.91). There were significant differences across time for DFOS scores (P<.001), demonstrating responsiveness to change. There were no floor or ceiling effects. The DFOS demonstrates acceptable psychometric performance as an outcome and screening measure for dancers. The 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 2019;49(2):64-79. Epub 27 Jul 2018. doi: 10.2519/jospt.2019.8247.