To investigate the correlation between the Disease Activity Score using a 28-joint count (DAS28) based on physician-derived joint counts and the DAS28 based on patient-derived joint counts (Pt-DAS28) in rheumatoid arthritis (RA).
Data from a multicenter, open-label study investigating the immunogenicity of etanercept (ETN) were analyzed. ETN-naive patients with active RA received ETN 50 mg once weekly alone or with methotrexate (MTX). Joint counts were performed at baseline, Week 12, and Week 24 by the physician and patient independently. Patients received instruction in performing joint assessments.
Of 447 patients enrolled (ETN, n = 218; ETN + MTX, n = 229), most were women (79%) and the mean age was 54.5 years. Correlation coefficients between DAS28 and Pt-DAS28 were > or = 0.57 at baseline, Week 12, and Week 24. At Week 24, 48%, 39%, and 12% of patients could be classified as having low, moderate, or high disease activity, respectively, using DAS28. Using Pt-DAS28, 43%, 39%, and 18% were similarly classified. Agreement in the category of disease activity classification occurred in 72% of patients (kappa = 0.55). At Week 24, 78% of patients using DAS28 and 72% of patients using Pt-DAS28 were classified as moderate or good European League Against Rheumatism responders.
These results support the possible use of patient-derived tender and swollen joint counts to aid in the assessment of disease activity and clinical response in patients with RA.