To identify factors associated with radiographic progression at 52 weeks in patients with rheumatoid arthritis (RA) after 12 weeks of methotrexate (MTX) therapy.
The study population consisted of patients from the MTX arm of the Trial of Etanercept and Methotrexate with Radiographic Patient Outcomes (TEMPO). Logistic regression analysis was used to identify clinical and laboratory assessments performed at Week 12 of MTX therapy that might be associated with Week 52 radiographic outcome (modified total Sharp score). Classification and regression tree (CART) modeling of the Week 12 assessments was used to determine the subgroups of patients with the best and worst radiographic outcomes.
A total of 169 patients were analyzed: 116 patients in the best radiographic outcome group and 53 patients in the worst radiographic outcome group. Logistic regression analysis showed that Week 12 C-reactive protein (CRP) level, erythrocyte sedimentation rate, tender joint count, swollen joint count (SJC), and Health Assessment Questionnaire scores were significantly associated with radiographic progression at Week 52 (p < 0.05 for each assessment). CART modeling showed that patients with Week 12 CRP > 0.67 mg/dl and SJC > 1 and patients with Week 12 CRP ≤ 0.67 mg/dl and SJC > 10 were likely to show the worst radiographic progression at Week 52. The CART model had a sensitivity of 85%, specificity of 60%, and overall classification accuracy of 68%.
In patients with RA, measures of CRP and SJC after 12 weeks of MTX therapy emerged as the factors most associated with radiographic progression at Week 52.