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Effects of language, insurance and race/ethnicity on measurement properties of the PROMIS Physical Function Short Form 10a in rheumatoid arthritis

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Izadi Z1, Katz PP2, Schmajuk G3, Gandrup J2, Li J2, Gianfrancesco M2, Yazdany J2. Arthritis Care Res (Hoboken). 2018 Aug 12. doi: 10.1002/acr.23723. [Epub ahead of print]


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1 Department of Epidemiology and Biostatistics, University of California San Francisco, San Francisco, CA.

2 Division of Rheumatology, University of California San Francisco, San Francisco, CA.

3 Division of Rheumatology, San Francisco Veterans Affairs Medical Center, San Francisco, CA.


OBJECTIVE: Most studies evaluating patient-reported outcomes such as the PROMIS Physical Function Short Form 10a (PF10a) in rheumatoid arthritis (RA) have been performed in Caucasian and English-speaking populations. We assessed the measurement properties of the PF10a in a racially/ethnically diverse population with RA. We determined 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 PF10a's use, 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 whites, English-speakers and privately-insured patients. However, constructs evaluated by the PF10a were less correlated with clinical measures among Chinese-speakers and Hispanics, 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.