Diagnostic accuracy of cartridge-based nucleic acid amplification test and resistance pattern in new and previously treated tuberculosis cases: A prospective observational study

Abstract

Background: Diagnostic methods, particularly sputum microscopy, are the standard method for diagnosing tuberculosis (TB) in many settings. The emergence of cartridge-based nucleic acid amplification test (CBNAAT) as a newer diagnostic tool for TB has shown promising results. CBNAAT is a rapid molecular test that detects the genetic material of Mycobacterium tuberculosis (MTB), the bacterium causing TB, in sputum samples. It offers higher sensitivity and faster results compared to sputum microscopy. Aim: The study aimed to 1) compare the diagnostic accuracy of CBNAAT in detecting smear-positive and smear-negative pulmonary TB cases, and 2) compare rifampicin resistance prevalence between newly diagnosed and previously treated pulmonary TB patients. Methodology: A hospital-based prospective study was conducted in the Respiratory Medicine Department of Guru Gobind Singh Government Hospital, Jamnagar, on PTB patients from August 2019 to December 2020. Data were collected through a self-structured questionnaire that included detailed clinical history, radiological, biochemical, and microbiological investigations. Descriptive statistical analyses were performed to present data as percentages and frequencies. Diagnostic accuracy analysis was conducted. A P-value <0.05 was considered significant. Results: Out of 150 cases, 104 (69.3 %) were male, while 46 (30.7%) were female. Sixty-one percent of new and 86% of previously treated cases were male, whereas 39% of new and 14% of previously treated cases were female. The sensitivity of sputum smear microscopy is 77.33% in cases of PTB, whereas sputum CBNAAT detected 94% of cases of PTB. The sensitivity of CBNAAT for MTB detection in smear microscopy–positive samples was 93.97%, whereas the sensitivity in smear microscopy–negative samples was 94.12%. Regarding rifampicin resistance, the prevalence was lower in newly diagnosed (3/100) compared to previously treated patients with rifampicin-resistant PTB (3/50). Conclusion: These findings suggest that CBNAAT can be a valuable tool for the detection of TB, particularly in cases where sputum smear microscopy results are negative. However, further research is needed to validate these results and evaluate the clinical implications of using CBNAAT in routine TB diagnostics.