Interferon Gamma as a Biomarker in Tuberculosis Diagnosis in a Tertiary Care Centre

Abstract

Introduction: Tuberculosis (TB) is a major global health concern, with India accounting for a significant proportion of cases. Interferon-gamma (IFN-γ), a Th1 cytokine, is a potential biomarker for TB diagnosis. Currently, Interferon-gamma for Tuberculosis diagnosis is primarily used for research purposes only and is not commercially available for routine clinical use. The role of interferon gamma in TB patients has been evaluated in previous studies, however due to inconclusive results, this current study has been undertaken to compare blood IFN-γ levels in Tuberculosis patients versus healthy controls to evaluate its utility as a diagnostic biomarker for TB.

Objectives: To compareblood IFN-γ levels between Tuberculosis patients and healthy controls at a tertiary care centre to assess the utility of IFN-γ as a biomarker for TB diagnosis.

Methods: A cross-sectional study was conducted over a period of four months from November 2024 to February 2025 at the Department of Respiratory Medicine, Karpaga Vinayaga Institute of Medical Sciences, Chengalpattu. 60 participants were enrolled, including 30 newly diagnosed patients with TB (sputum-positive pulmonary TB, smear-negative pulmonary TB, and extrapulmonary TB) versus 30 healthy controls. Demographic and clinical data were also recorded. Venous blood (5 ml) was analysed for IFN-γ using a quantitative sandwich enzyme immunoassay.

Results: The mean age was 44.00±14.00 years in the TB group and 42.27±10.22 years in the control group (p = 0.586). The mean BMI was identical at 24.57±1.92 in both groups (p = 1.000). Females comprised 50% of TB patients and 60% of Healthy individuals (p = 0.436). Smoking was reported in 16.7% of TB patients and 6.7% of Healthy individuals (p = 0.228), whereas alcohol use was observed in 30% of TB patients and 16.7% of Healthy individuals (p = 0.222). Median IFN-γ was significantly higher in TB patients (203.0 pg/ml; IQR:18.7–485.0) compared to Healthy individuals (11.9 pg/ml; IQR:8.2–16.0) (p < 0.0001). At a cut-off of 17.1 pg/ml, IFN-γ yielded an AUC of 0.995, with sensitivity, specificity, PPV, NPV, and accuracy all at 96.67%.

Conclusions: Serum IFN-γ levels were significantly higher in active TB patients than in healthy controls. These results support IFN-γ as a reliable biomarker for TB diagnosis, especially in high-burden settings.