The Usefulness of the Patient-Reported Outcomes Measurement Information System Scale v1.2 Global Health for Assessing Mental and Physical Health of Individuals With Chronic Musculoskeletal Pain, Rheumatoid Arthritis, and Hip and Knee Osteoarthritis or Undergoing Physiotherapy: Results of Factor and Item Response Theory Analyses.

OBJECTIVE

This study aims to evaluate 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.

METHODS

PROMIS-GH was administered to 4,295 individuals (mean ± SD age 56 ± 14 years, 70% female, chronic musculoskeletal pain [n = 1,142], rheumatoid arthritis [n = 1,987], hip/knee osteoarthritis [n = 418], and 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 item response theory [IRT] assumptions [unidimensionality, local independence, and monotonicity] and graded response model fit), the ability of the subscales to discriminate different levels of health (items' discrimination parameters α) to cover the relevant range of GMH and GPH (range of difficulty parameters β) and their precision (item- and subscale-level information), and to compare demographic and clinical subgroups (differential item functioning [DIF]).

RESULTS

It is legitimate to calculate a GMH and a GPH subscale score (comparative fit index = 0.98/0.97, Tucker-Lewis index = 0.97/0.95, root mean square error of approximation = 0.15/0.19, and standardized root mean square residual = 0.05/0.07) and to convert raw scores to interval scores (IRT assumptions met and adequate 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 demographic and clinical subgroups (no DIF).

CONCLUSION

PROMIS-GH can be used to measure GMH and GPH in individuals with musculoskeletal disorders. Replacement or improvement of the Global10 item could be considered.