Objective: To identify patients at high risk of relapse after anti-tuberculosis (TB) therapy or with poor long-term outcomes.

Methods: Fifty-one patients with pulmonary TB: 7 were classified as high association with both cavitations on initial chest radiography and positive sputum smear/cultures after two months of anti-TB treatment (HA group); 19 medium association (MA, one risk alone); and 25 low association (LA, neither risk). Serum interferon (IFN)-γ-inducible protein 10 (IP-10), interleukin-17 (IL-17), and C-reactive protein levels were investigated.

Results: There was a trend towards higher serum IP-10 levels (p= 0.042) for HA patients throughout the 6-month treatment period. Month-2 IP-10 levels were higher in the HA than in the MA/LA group (656.2±234.4 vs. 307.6±258.5 pg/ml, adjusted p= 0.005). Receiver operating characteristic curves showed that the risk of relapse was well-captured by month-2 IP-10 levels at a cut-off value of 431 pg/ml (AUC= 0.857, 95% CI 0.75–0.97, p= 0.003). Month-2 serum IL-17 levels were lower in non-survivors than survivors (15.7±2.9 pg/ml vs. 24.6±8.2 pg/ml, p= 0.001). Multivariate analysis demonstrated that a month-2 serum IL-17 level of⩽ 17 pg/ml (p= 0.026) was independently associated with all-cause mortality. Conclusions: Serum IP-10 and IL-17 levels after 2 months of anti-TB treatment may be biomarkers for estimating risk of both cavitation and delayed sputum conversion, and for predicting long-term mortality, respectively.