Refining the Measurement of Disablement: A Many-Faceted Rasch Analysis of the Disablement in the Physically Active Scale-Short Form 8

The Disablement in the Physically Active Scale-Short Form 8 assesses disablement in physically active individuals. Previous studies using classical test theory have limitations; many-faceted Rasch analysis addresses these limitations and offers other insights into the scale’s psychometric properties, including total score validity. This study used many-faceted Rasch analysis to confirm the Disablement in the Physically Active Scale-Short Form 8’s structure and assess other psychometric properties. A total of 619 physically active individuals (mean age = 26.30 ± 13.25 years; 312 females, 306 males) with musculoskeletal injuries completed the questionnaire during outpatient rehabilitation. Rasch analysis evaluated model-data fit, rating scale functionality, item-person mapping, item/subscale difficulty, and person ability. Results indicated no misfit items, with both subscales showing good model-data fit. Item difficulty ranged from −0.45 to 0.70 logits, and subscale difficulty from −0.77 to 0.77 logits, indicating limited dispersal. Person ability varied widely (−4.51 to 5.61 logits). A concern emerged regarding limited differentiation between the first two response options, suggesting a need to improve scale sensitivity. Many-faceted Rasch analysis supports the Disablement in the Physically Active Scale-Short Form 8’s psychometric soundness and the use of a total summary score. Future work should refine the scale to enhance measurement precision and reduce floor and ceiling effects.