Invariance Testing of the Disablement in the Physically Active Scale

Context: The increased emphasis on implementing evidence-based practice has reinforced the need to more accurately assess patient improvement. Psychometrically sound, patient-reported outcome measures are essential for evaluating patient care. A patient-reported outcome instrument that may be useful for clinicians is the Disablement in the Physically Active Scale (DPAS). Before adopting this scale, however, researchers must evaluate its psychometric properties, particularly across subpopulations.

Objective: To evaluate the psychometric properties of the DPAS in a large sample using confirmatory factor analysis procedures and assess structural invariance of the scale across sex, age, injury status, and athletic status groups.

Design: Observational study.

Setting: Twenty-two clinical sites.

Patients or other participants: Of 1445 physically active individuals recruited from multiple athletic training clinical sites, data from 1276 were included in the analysis. Respondents were either healthy or experiencing an acute, subacute, or persistent musculoskeletal injury.

Main outcome measure(s): A confirmatory factor analysis was performed on the full sample, and multigroup invariance testing was conducted to assess differences across sex, age, injury status, and athletic status. Given the poor model fit, alternate model generation was used to identify a more parsimonious factor structure.

Results: The DPAS did not meet contemporary fit index recommendations or the criteria to demonstrate structural invariance. We identified an 8-item model that met the model fit recommendations using alternate model generation.

Conclusions: The 16-item DPAS did not meet the model fit recommendations and may not be the most parsimonious or reliable measure for assessing disablement and quality of life. Use of the 16-item DPAS across subpopulations of interest is not recommended. More examination involving a true cross-validation sample should be completed on the 8-item DPAS before this scale is adopted in research and practice.