The Patient‐Reported Outcomes Measurement Information System scale v1.2 Global Health (PROMIS‐GH) is useful to assess mental and physical health in individuals with chronic musculoskeletal pain, rheumatoid arthritis, hip/knee osteoarthritis, or people undergoing physiotherapy: Results of factor and item response theory analyses

This study aims to assess whether the 10-item Patient-Reported Outcomes Measurement Information System Scale v1.2-Global Health (PROMIS-GH) is useful to assess Global Mental Health (GMH) and Global Physical Health (GPH) in individuals with musculoskeletal disorders. PROMIS-GH was administered to 4295 individuals (mean±SD age 56±14y, 70% female, chronic musculoskeletal pain [n=1142], rheumatoid arthritis [n=1987], hip/knee osteoarthritis [n=418], undergoing physiotherapy [n=947]). We investigated the legitimacy of calculating a GMH and a GPH subscale score (Confirmatory Factor Analyses) and of converting raw ordinal subscale scores to interval scores (checking IRT-assumptions [unidimensionality, local independence, monotonicity] and Graded Response Model fit), the ability of the subscales to discriminate different levels of health (items' discrimination parameters α), to cover relevant range of GMH and GPH (range of difficulty parameters β), their precision (item- and subscale-level information), and to compare demographical and clinical subgroups (Differential Item Functioning [DIF]). It is legitimate to calculate a GMH and a GPH subscale score (CFI=0.98/0.97, TLI=0.97/0.95, RMSEA=0.15/0.19, SRMR=0.05/0.07), and to convert raw scores to interval scores (IRT-assumptions met and model fit). Discrimination (items' α≥2), coverage (lowest β≤-2) and precision (reliability≥0.70 for large portions of the health domain) were adequate for all items, except item Global10, underscoring that they can distinguish individuals with different levels of GMH and GPH with precision. The subscales can be used to compare demographical and clinical subgroups (no DIF). The PROMIS-GH can be used to measure GMH and GPH in individuals with musculoskeletal disorders. Replacement or improvement of item Global10 could be considered.