Objective: To estimate the contributions of health-related quality of life domains to the patient global assessment of disease activity (PtGA) in rheumatoid arthritis (RA). Methods: Data are drawn from baseline visits of 2 observational RA cohorts. Participants completed forms for patient-reported outcome measures, including PtGA and measures from the Patient-Reported Outcomes Measurement Information System, and clinical data were collected. Factor analysis was used to identify latent variables, and multivariable linear regression was used to estimate determinants of the PtGA. Results: Patients were mostly female (81%), white (78%), and had established disease (mean ± SD 12.3 ± 10.7 years), with 62% in remission or having low disease activity. In cohort 1 (n = 196), the following 2 factors emerged: 1) daily function (moderate-to-strong [i.e., >|0.65|] loadings of physical function, pain interference, social participation, and fatigue, and weak [>0.35] loadings of sleep disturbance); and 2) emotional distress (strong loadings of depression and anxiety). In crude analysis, daily function explained up to 53% and emotional distress up to 20% of the variance in PtGA. In both cohorts, in adjusted analyses, daily function and, to a much lesser extent, swollen joint count independently predicted PtGA; age was inversely related to PtGA in cohort 1 only. Conclusion: These findings suggest that in patients with RA, PtGA ratings largely reflect the extent to which patients feel they can function in everyday roles and are not impacted by mood. This suggests that higher than expected PtGA scores may offer an opportunity to discuss patient expectations regarding roles and activities and the impact of their RA symptoms on daily function.
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