Abstract Objectives Physical function in RA is largely influenced by multiple clinical factors; however, there is a growing body of evidence that psychological state and other comorbidities also play an essential role. Using data obtained in the COVAD study, an international self-reported e-survey, we aimed to a) explore the predictive ability of sociodemographic and clinical variables on PROMIS physical function short form-10a (PROMIS PF-10a) in RA and b) to investigate variation in disease activity and functional outcomes based on country-level socio-economic parameters. Methods Patient demographics, disease characteristics including current symptom status, functional status and treatment variables as well as income level of the country of residence, were extracted from survey responses. PROMIS PF-10a scores were compared across country income levels. The influence of extracted variables on reversed PROMIS PF-10a scores were investigated using negative binomial univariable- and multi-variable regression. Results A total of 1,342 RA patients were included in this analysis. In the optimised parsimonious predictive model for reversed PROMIS PF-10a, older age, female gender, disease duration, fatigue and pain levels were independently associated with worse physical function, whereas Asian ethnicity, higher overall physical health ratings, ability to carry out everyday activities, and residing in a country with an upper-middle or high-income level were independently associated with better physical function. Conclusion Our study highlights that clinical factors remain strong predictors of physical function in RA, irrespective of individual and country-level socioeconomic differences. Interestingly, high country-level income was associated with better physical function, irrespective of individual sociodemographic and clinical factors.
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