TNF and rheumatoid arthritis: Taking into account the clinical and demographic factors previously shown by our group and others to influence response to anti-TNF treatment in RA patients (DAS28 score at baseline, HAQ score, sex, concurrent DMARD therapy, rheumatoid factor positivity, and smoking habits), the variance in the absolute change in the DAS28 at 6 months of followup in the combined cohort was 15%.