CXCR3 ligands as clinical markers for pulmonary tuberculosis

SETTING: A tertiary care academic medical centre. OBJECTIVE: To evaluate the clinical usefulness of CXC chemokine receptor 3 (CXCR3) ligands in active pulmonary tuberculosis (TB). DESIGN: Patients with various pulmonary diseases and healthy controls were recruited into this cross-sectional study. Plasma levels of interferon-gamma (IFN-gamma) and the CXCR3 ligands (CXCL9 [monokine induced by IFN-gamma, MIG], CXCL10 [IFN-gamma-inducible 10-kDa protein, IP-10] and CXCL11 [IFN-inducible T-cell alpha chemoattractant, I-TAC] were measured using enzyme immunoassays. RESULTS: The study included 846 subjects: 201 patients with active pulmonary TB, 389 with other pulmonary diseases, and 256 controls. CXCR3 ligand levels were higher in TB patients than in controls and all other disease groups, whereas the IFN-gamma levels did not differ. The area under the curve (AUC) for differentiating active TB from all other groups was 0.797 for CXCL9, 0.726 for CXCL10, 0.846 for CXCL11 and 0.534 for IFN-gamma. The AUC for differentiating active TB from controls was 0.926 for CXCL9, 0.818 for CXCL10, 0.865 for CXCL11 and 0.575 for IFN-gamma. CXCR3 levels correlated with sputum acid-fast bacilli smear grades and the radiographic extent of pulmonary TB. CONCLUSION: CXCR3 ligands may be useful surrogate markers for diagnosing active TB and for assessing TB patients clinically.