The role of systemic inflammatory markers in differentiating tuberculosis from nontuberculous mycobacterial colonization and infection: A retrospective observational study

Culture confirmation for tuberculosis (TB) and nontuberculous mycobacteria (NTM) is time-consuming, potentially delaying diagnosis and treatment. Identifying systemic inflammatory markers from routine blood tests may provide supportive information for differentiating TB from NTM infection or colonization. This study evaluates the diagnostic value of systemic inflammatory indices in distinguishing TB from NTM infection and colonization. This retrospective study included 480 patients diagnosed between January 2018 and December 2023. TB and NTM diagnoses were confirmed according to microbiological and clinical criteria. Hematological parameters, including neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, lymphocyte-to-monocyte ratio, lymphocyte-to-C-reactive protein ratio, systemic immune-inflammation index (SII), and systemic inflammation response index (SIRI), were analyzed. Receiver operating characteristic analysis was performed for parameters showing statistical significance in differentiating TB from NTM colonization. Among the inflammatory markers assessed, lymphocyte count and mean platelet volume were significantly higher in TB compared with NTM colonization, while SII and SIRI indices were significantly lower. Receiver operating characteristic analysis identified optimal cutoff values for lymphocyte count (1.895; sensitivity 57.7%, specificity 71.8%) and SII (2.345; sensitivity 73.1%, specificity 69.4%). The 95% confidence intervals for the area under the curve values are presented in table and figures. Lymphocyte count, mean platelet volume, SII, and SIRI show potential as supportive diagnostic markers for differentiating TB from NTM colonization. These indices may aid clinical decision-making while awaiting culture results; however, further studies with larger sample sizes and prospective validation are warranted.