Model Examining Factors Related to Physicians' Ratings of Disease Activity in Patients with Rheumatoid Arthritis

The data of 105 patients with rheumatoid arthritis (RA) were used to examine a model describing the interrelations among objective disease activity (DAS-28 Swollen Joint Count and Erythrocyte Sedimentation Rate), RA patient-rated disease activity (Rapid Assessment of Disease Activity in Rheumatology total joint score and disease activity), and the physician examination-based total joint tenderness rating (TJC), as determinants of physician-rated disease activity. This study also evaluated the association of patients' non-white ethnicity and depression with patient-rated disease activity scores. Structural equation modeling was adopted to elucidate the complexity of relations among variables in the proposed model and revealed a good fit of the data, x²{23}=32.51, p = 0.09, CFI = 0.96, RMSEA = 0.06. Objective disease activity was positively associated with patient-rated disease activity, TJC and physician-rated disease activity. The level of depressive symptomatology and non-white ethnicity were related to higher levels of patient-rated disease activity. While objective disease activity had a strong direct correlation with physician-rated disease activity, partial mediation was established because the strength of this association diminished when the model included the specified predictors. Specifically, as a sole predictor, the effect of objective disease activity on physician-rated disease activity was significant (β = .85, p < 0.001). The direct effect of objective disease activity on physician-rated disease activity was still significant but reduced after patient-rated disease activity and TJC were added to the model (β = .54, p < .01). Findings confirmed the importance of a multi-dimensional framework in evaluating RA disease activity assessment.