IFNG and tuberculosis: Although no significant differences were found for either tryptophan (p = 0.591) or IFN-γ levels (p = 0.432) between the TB-positive and the TB-negative of the total group, a potential bias was present in the fact that 14 TB-positive patients were from the HAART group (19 % of 75), and 10 TB-positive patients were from the HAART-naïve group (33 % of 30).