Effects of Language, Insurance, and Race/Ethnicity on Measurement Properties of the PROMIS Physical Function Short Form 10a in Rheumatoid Arthritis

Objective Most studies that have evaluated patient-reported outcomes, such as those utilizing the Patient-Reported Outcomes Measurement Information System (PROMIS) Physical Function Short Form 10a (PF10a) in rheumatoid arthritis (RA), have been performed in white and English-speaking populations. The aim of our study was to assess the measurement properties of the PF10a in a racially/ethnically diverse population with RA and to determine the effect of non-English language proficiency, insurance status, and race/ethnicity on the validity and responsiveness of the PF10a. Methods Data were abstracted from electronic health records for all RA patients seen in a university-based rheumatology clinic between 2013 and 2017. We evaluated the use of the PF10a, floor and ceiling effects, and construct validity across categories of language preference, insurance, and race/ethnicity. We used standardized response means and linear mixed-effects models to evaluate the responsiveness of the PF10a to longitudinal changes in the Clinical Disease Activity Index (CDAI) across population subgroups. Results We included 595 patients in a cross-sectional analysis of validity and 341 patients in longitudinal responsiveness analyses of the PF10a. The PF10a had acceptable floor and ceiling effects and was successfully implemented. We observed good construct validity and responsiveness to changes in CDAI among white subjects, English speakers, and privately insured patients. However, constructs evaluated by the PF10a were less correlated with clinical measures among Chinese speakers and Hispanic subjects, and less sensitive to clinical improvements among Medicaid patients and Spanish speakers. Conclusion While the PF10a has good measurement properties and is both practical and acceptable for implementation in routine clinical practice, we also found important differences across racial/ethnic groups and those with limited English proficiency that warrant further investigation.