Role of Cartridge Based Nucleic Acid Amplification Test in Diagnosing Tuberculous Empyema Thoracis – A Study from Telangana, India

Abstract

BACKGROUND The pleura is involved in pulmonary or systemic tuberculosis by various mechanisms like delayed hypersensitivity. Tuberculous empyema usually results from failure of a primary tubercular effusion to resolve and further progresses to chronic suppurative form. In tuberculous empyema, the pleural fluid is purulent, and is loaded with tuberculous organisms on direct acid-fast bacillus (AFB) smear examination and / or culture of pus. We need to assess the role of cartridge based nucleic acid amplification test (CBNAAT) in the diagnosis of tuberculous empyema. METHODS This study was a prospective observational study of all adult patients of empyema above 15 years of age, admitted in the Department of Pulmonology, over a period of 1 year, 6 months after obtaining clearance from ethical committee and proper consent from the study subjects. RESULTS A total of sixty-three (63) empyema cases were recruited and analysed further. On evaluation, we diagnosed 26 cases with tubercular aetiology (41.27 %) and remaining thirty-seven (58.73 %) cases with non-tubercular aetiology. CONCLUSIONS Pleural fluid (pus) cartridge based nucleic acid amplification test (CBNAAT) is very sensitive and provides a rapid confirmed diagnosis within 2 hrs. including drug susceptibility. In this study, sensitivity of CBNAAT in suspected tuberculous empyema patients was 88.5 % and specificity was 100 %. Pleural fluid CBNAAT is more sensitive in both pleural fluid AFB smear positive (100 %) and pleural fluid AFB smear negative (72.7 %) cases. So, pleural fluid and sputum direct AFB smear and CBNAAT should be sent in all suspected tuberculous empyema cases for early diagnosis of tuberculosis and early detection of rifampicin resistance. KEY WORDS Mycobacterium Tuberculosis, Tubercular Empyema, Pleural Fluid, CBNAAT, AFB, Anti-Tubercular Drugs