IFNG and rheumatoid arthritis: Non-stimulated neopterin levels were positively correlated with IFN-γ levels (r = 0.280, p<0.05) and ESR assessed at baseline (r = 0.315, p<0.05), and TB-antigen stimulated neopterin levels were positively correlated with IFN-γ levels (r = 0.322, p<0.05) and DAS28 score assessed at baseline (r = 0.310, p<0.05) in RA patients.