Could neutrophil to lymphocyte ratio be a prognostic predictor of relapse in patients with extra-pulmonary tuberculosis?

Background: We aimed to evaluate whether neutrophil to lymphocyte ratio (NLR) was associated with relapse occurrence during the follow-up of extra-pulmonary tuberculosis (EPTB). Material and Methods: We retrospectively collected data from 408 EPTB patients hospitalized between 1996 and 2015. We evaluated the performance of NLR in predicting relapse and to stratify patients into high and low level groups. Kaplan-Meier method was used to generate regression-free survival (RFS) curves, which were compared by Logrank test according to NLR categories. Results: Fourteen cases developed a relapse (3.4%). The median value of NLR was significantly higher in patients with relapse (3.8 +/- 1.4 vs 2.7 +/- 1.4; p=0.008). Receiving operating characteristics (ROC) curves analysis showed that NLR had an Area under the ROC (AUROC) of 0.73 in predicting relapse (p=0.003). At a cut-off of 3, NLR had a sensitivity of 64% and a specificity of 70% to predict relapse. Survival curves showed that patients with a high NLR (>= 3) had shorter RFS compared with those with a low NLR (<3) (24.7 vs 44.2 months; p=0.04). High NLR was significantly associated with relapse both in univariate (HR=3.7; p=0.041) and multivariate Cox regression analysis (HR=5.24; p=0.027). Conclusion: NLR may have a prognostic value in the follow up of patients with EPTB.