The extended oligoarticular subtype is the best predictor of methotrexate efficacy in juvenile idiopathic arthritis

Objective: To determine whether demographic, clinical, and laboratory varia bles measurable at baseline predict the clinical efficacy or major toxic ef fects of methotrexate (MTX) therapy in children with chronic arthritis. Study design: Patient eligibility criteria: (1) monitored in our unit betwe en 1986 and 1996 with a diagnosis of chronic arthritis and (2) treatment wi th MTX as the sole second-line agent and for at least 6 months. Outcomes in vestigated: (1) short-term (6-month) clinical response, (2) complete diseas e control, (3) disease relapse after MTX discontinuation after complete dis ease control, (4) aminotransferase elevation, (5) gastrointestinal toxicity . Independent variables that showed significant results with univariate tes ts or were clinically relevant for each outcome underwent multiple logistic or Poisson regression analyses. Results: Eighty patients were available for analysis. The disease onset sub type was systemic in 37 patients, polyarticular in 20 patients, and oligoar ticular in 23 patients (all with polyarticular course: extended oligoarticu lar subtype). The extended oligoarticular subtype was the best predictor fo r both the short-term clinical response (odds ratio 6.80, P = .02) and, tog ether with a better functional ability, the complete disease control (rate ratio 3.85, P = .03 and rate ratio 3.29, P = .006, respectively). Patients with this subtype of chronic arthritis tended to have earlier, and more fre quently, a disease relapse after MTX discontinuation. Thrombocytosis was th e only significant risk factor for liver biochemical abnormalities (rare ra tio 2.94, P = .008), whereas no variable yielded significant results for ga strointestinal toxicity. Conclusion: Patients with extended oligoarticular chronic arthritis were mo re likely to benefit from MTX therapy and to have a relapse after treatment discontinuation, suggesting that MTX is distinctly more effective in this subset of chronic arthritis.