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

Abstract

• 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 preprofessional adult dancers. • METHODS: 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. • RESULTS: 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 (á = .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. • CONCLUSION: 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