Evaluation of musculoskeletal discomfort using item response theory: creation of a scale based on the self-reported pain symptoms.

This study aims to build a scale for musculoskeletal discomfort based on the self-reported musculoskeletal pain by individuals. For this, methods such as factorial analysis and item response theory were used. A sample of 1821 workers of a footwear industry participated in this study. The scale consists of four levels ranging from mild to maximum discomfort. In mild discomfort (level 60), pain symptoms are rare or frequent in regions such as cervical and trapezoidal area, low back, shoulders, wrists, ankles and feet. At level 70, rare or frequent symptoms affect regions of the upper and lower limbs. At level 80, frequent symptoms become common in the trunk and in most of the upper and lower limbs. At level 90, the symptoms become daily in elbows, thighs and knees. The scale showed signs of validity and proved useful for studies in ergonomics. Methods such as factor analysis and item response theory were used to build a four-level musculoskeletal discomfort scale that can be useful to complement the screening process for workers with musculoskeletal pain. The scale shows signs of accuracy, in addition to validity and reliability. WMSD: work-related musculoskeletal disorders; CTT: classic test theory; IRT: item response theory; KMO: Kaiser-Meyer-Olkin; PR: pain rarely; PO: pain often; PE: pain everyday; DIF: differential item functioning.