Role of QuantiFERON-TB Gold in diagnosis of Tuberculosis

Introduction: The definitive diagnosis of Tuberculosis is established when typical histological features can be demonstrated or mycobacteria can be isolated from the body fluids or from sputum or from gastric lavage. Various other methods, such as gel electrophoresis, radiometric assay and polymerase chain reaction are also available. It is well documented that isolation of mycobacteria and culture is difficult and time consuming and other tests are complex and technically more demanding. In this study, we correlated the results of QuantiFERON-TB Gold test with tuberculin skin test and sputum positivity. Material and methods: Total 150 subjects were included in this study. The clinical features and detailed history of each case was recorded in a standard format including exposure to infection and physical examination. Patients were tested for QuantiFERON-TB Gold. Results: The results obtained in this study showed that single method for diagnosis of tuberculosis patients may not be able to detect all the positive cases of tuberculosis. Whereas combining two methods for the diagnosis of tuberculosis patients is more advantageous way for the detection of tuberculosis patients. The combination of tuberculin skin test along with the QuantiFERON-TB Gold test had yield 96.6% cases as positive in our study which is far better than using a single test. Conclusion: Use of QuantiFERON-TB Gold test for the diagnosis of tuberculosis is superior to conventional methods of diagnosis, above which the QuantiFERON-TB Gold test in combination with tuberculin skin test yields the maximum number of true positive cases of tuberculosis. The levels of new markers, serum interferon gamma (IFN-γ) after stimulation by foreign antigen by QFT test and combining it with tuberculin skin test yields a good amount of true positive cases of tuberculosis even in latent cases.