Neutrophil-to-lymphocyte ratios as easy-to-use biomarkers for the diagnosis of active tuberculosis in children and adolescents

Background The diagnosis of active tuberculosis (ATB) in children and adolescents is limited by non-specific symptoms, paucibacillary infection, and the low sensitivity of traditional tools. These limitations can lead to delayed treatment and increased complications. Methods This retrospective study recruited 1,080 participants. We performed receiver operating characteristic (ROC) curves to evaluate the diagnostic performance of logarithmic neutrophil-to-lymphocyte ratio (logNLR) for ATB infection. We employed logistic regression, restricted cubic spline (RCS), stratified, and interaction analyses to evaluate the association between logNLR and ATB infection. Results The logNLR was significantly associated with ATB infection in the adjusted model (OR = 1.38, 95% CI: 1.01-1.88, P = 0.044). The RCS curve indicated a non-linear relationship between logNLR and ATB infection, with the critical threshold of 0.9232. The breakpoint analyses further confirmed that when logNLR Mycobacterium tuberculosis (MTB) exposure, and participants with CD4+ T cell counts>414 cells/μL or CD8+ T cell counts>238 cells/μL (all P Conclusions The logNLR is a simple, low-cost, and effective biomarker for diagnosis of ATB in children and adolescents. The critical threshold and breakpoint of logNLR enable precise risk stratification, providing valuable support for early ATB identification in this population.