A study on early detection of pulmonary tuberculosis in smear negative retroviral positive patients by using CBNAAT

ABSTRACT

Background: Tuberculosis is one of the most common opportunistic infections among people with HIV infection. Detection of pulmonary tuberculosis by sputum-based techniques includes microscopy and culture. However, in people living with HIV, sputum production is scanty and also the sputum contains less number of bacilli due to fewer cavitations, thereby decreasing the sensitivity and specificity of sputum microscopy as a diagnostic tool. Aim of the study In this study, we assess the usefulness of CBNAAT in the early detection of pulmonary tuberculosis and its incidence by using CBNAAT in smear-negative HIV patients using mycobacterial culture in Lowenstein Jensen medium as Gold Standard. Materials and methods: The study was conducted in the Department of Cardiothoracic Surgery, Government Mohan Kumaramangalam Medical College Hospital. Data were collected from 150 HIV infected patients who tested sputum smear negative. Sputum samples were then sent for CBNAAT and sputum culture for mycobacteria. Results: Of the 150 patients enrolled, 28(18.66%) of them were detected with MTB by CBNAAT; whereas sputum culture could detect 38(25.33%) of them. Thus, compared to sputum smear, CBNAAT increases TB detection by 18.66% and sputum culture increases by 25.33%. The sensitivity of CBNAAT in our study was 73.68% and the incidence of smear-negative pulmonary TB in the study population by using CBNAAT was 18.66%. Conclusion: CBNAAT is a highly sensitive and diagnostic stool for the diagnosis of pulmonary TB and it is of immense help in the early diagnosis of smear-negative pulmonary TB in HIV infected patients. Therefore, CBNAAT should be used as the initial test in HIV infected patients suspected with pulmonary TB.