A Study on the Evaluation of CBNAAT -A Novel Diagnostic tool for Rapid and Specific Diagnosis of Mycobacterium Tuberculosis in Pulmonary and Extrapulmonary Specimens in a Tertiary Care Hospital of South India

Background: Among the infectious diseases Tuberculosis (TB) is one of the most dangerous threats to public health . As per the Global TB report 2017 the estimated incidence of TB in India was approximately 28,00,000 accounting for about a quarter of the world’s TB cases . We need accurate feasible, rapid and affordable diagnostic tool to detect Mycobacterium Tuberculosis . Among various investigations in diagnosis of TB, Genexpert which was recently endorsed by WHO remains one of the rapid method to detect Mycobacterium Tuberculosis in both pulmonary and extra pulmonary specimens. Recently, there has been increasing evidence that supports the use of this assay in clinical samples other than sputum for patients with Extra Pulmonary TB. Materials and Methods: This is a retrospective observational study conducted in Department of Pulmonary medicine in Kanyakumari government medical college hospital. Pulmonary and extra pulmonary specimens taken from the patients which included outpatients and inpatients attending the tertiary care centre with TB suspect . Around 6638 samples taken from July 2017 to 2018 December were included in the study.Both pulmonary and extra pulmonary samples were taken for the study after informed consent. Gene Xpert System is equipped with GX2.1 software; computer; printer; barcode ;wand-reader and operator manual (Cepheid Inc, Sunnyvale, USA),this is available in a one, two, four, or 16-module configuration The Gene Xpert Cartridge is a single-use disposable cartridge all the processes including Sample extraction, amplification and detection are all carried out within this self-contained cartridge. The sputum sample collected from the patient with suspected TB is mixed with the reagent that is provided with the assay, and a cartridge containing this mixture is placed in the GeneXpert machine further processing from this point is fully automated. Results: About 6638 samples have been taken from July 2017 to 2018 December . Out of this 1152 samples detected Mycobacterium tuberculosis. Out of this 1111 were sensitive to rifampicin and 41 were resistant to rifampicin. 5486 samples did not detect Mycobacterium tuberculosis. 41 cases where positive for HIV . 1073 samples were pulmonary while 79 samples were extrapulmonary which included specimens from CSF, Pleural fluid & Ascitic fluid . Conclusion: From this study We concluded that the MTB/RIF test is a simple method to detect MTB. In conclusion, this assay not only has better sensitivity and specificity for the diagnosis of TB and detection of rifampin resistance in few hours, but also requires minimal biosafety measures. However, the new molecular technique is considerably more expensive, because of the high price of reagents and instrument maintenance, than conventional methods. Still this assay has a high clinical application value in earlier diagnosis of both pulmonary and extra pulmonary TB which can be applied for the early diagnosis and treatment of the disease.