Utility of CBNAAT in diagnosis of mycobacterium tuberculosis in a tertiary care teaching hospital in South India

Abstract

Background: Tuberculosis is the ninth leading cause of death worldwide. India contributes to about one fifth of global TB burden. It is very important to diagnose early and treat Tuberculosis to cut down transmission of Tuberculosis. Material and Methods: We conducted a retrospective study in department of Pulmonary medicine to analyze the utility and yield of CBNAAT from Jan- Dec 2017. We included all patients who were subjected to CBNAAT in the study period. Data was collected from ART centre, DOTS centre and CBNAAT centre. We collected total number of samples tested for CBNAAT, indication for CBNAAT, HIV status, result of smear microscopy for AFB and CBNAAT. Results: A total of 1703 samples were tested in CBNAAT during the study period. Mean age of the study population was 35.5±10.2 years. 1366 tested were negative and 290 samples were positive for CBNAAT. Of these 290 positive samples, 267 were sputum/BAL samples and 23 were extra pulmonary samples. We found rifampicin resistance rate of 2.4% (8/329) in pulmonary tuberculosis cases, There were no rifampicin resistance detected in extra pulmonary samples. CBNAAT could identify 184 cases (13.3%) that were smear negative. We found TB- HIV coinfection rate of 10.02%. Conclusions: We found CBNAAT to be an important diagnostic modality especially in sputum negative patients for early diagnosis and treatment. We could detect Mycobacterium tuberculosis in 13.4% of patients with negative smear for microscopy. In PLHIV, CBNAAT detected Mycobacterium Tuberculosis in 9.3% of patients. We found rifampicin resistance rate of 2.4% (8/329) in pulmonary tuberculosis cases. Keywords: CBNAAT; Tuberculosis; Smear negative; PLHIV.