Extension of the treatment duration is usually recommended in severe and disseminated TB, cavitary TB, positive 2-month M. tb culture, and delayed treatment responses, although no consensus regarding absolute indications has been established.16,23,24 From our results, patients without significant decreases in CXCR3 ligand levels during the initial 2 months had a higher incidence of treatment extension after the standard 6 months of therapy than did those with significant decreases in CXCR3 ligand levels. The gene discussed is CXCR3; the disease is tuberculosis.