Serial Estimation of IFN-γ and IP-10 as Biomarkers of Pulmonary Tuberculosis: A Longitudinal Study

Introduction: Tuberculosis is a chronic disease caused by the bacterium Mycobacterium tuberculosis, affecting the whole world, especially the South Asian region. Despite scientific advancements in its diagnosis and treatment, its incidence continues to be high. The treatment of TB usually requires a long course. Cell-mediated immunity is the mainstay of the host response in TB, and a number of cytokines are released in this process. Because these cytokines reflect the state of immune activation in the body, their estimation can be used for both screening and monitoring of patients once treatment has been initiated. The adequacy of treatment for active cases is an important determinant of the transmissibility of the disease in the community. Such a study has not been reported previously in Uttarakhand. These factors, along with the wide variations in literature, necessitated the study. Aim: To observe the changes in two biomarkers Interferon Gamma (IFN)-γ and Interferon Gamma-inducible Protein (IP-10) in tuberculosis patients during the course of their treatment. Materials and Methods: A longitudinal study was conducted on TB patients in the Department of Physiology, in collaboration with department of Microbiology, Himalayan Institute of Medical Sciences, Swami Rama Himalayan University, Dehradun, Uttarakhand, India. October 2022 to September 2023 among 35 pulmonary Tuberculosis (TB) patients. IFN-γ and IP-10 levels in their serum were estimated using the sandwich Enzyme-linked Immunosorbent Assay (ELISA) technique. Baseline estimations were followed by two repeat estimations at two months and six months of treatment. Statistical analysis of the data obtained was performed using Statistical Package of Social Sciences (SPSS) version 17.0 with repeated measures Analysis of Variance (ANOVA), and a p-value <0.05 was considered statistically significant. Results: The subjects had a mean age of 40.11±20.32 years. The mean IFN-γ and IP-10 levels were 46.93±24.55 pg/mL and 39.68±51.20 pg/mL, respectively. Their levels reduced during the course of treatment, as revealed by serial measurements at two months (IFN-γ: 9.41 pg/mL, IP-10: 9.21 pg/mL) and six months (IFN-γ: 9.14 pg/mL, IP-10: 3.34 pg/mL). This pattern was statistically significant (p-value <0.001). The reduction was steeper in the first two months and was more marked for IFN-γ, as indicated by their effect size. The results were similar for both genders. Conclusion: Effective therapy led to reduced levels of IFN-γ and IP-10, suggesting that serial measurements of these biomarkers could be utilised to monitor the response to therapy in tuberculosis patients.