Utility of CBNAAT in Smear-Negative Pulmonary Tuberculosis: A Prospective Evaluation

Abstract

Background: Smear-negative pulmonary tuberculosis (PTB) poses a major diagnostic challenge, especially in high-burden countries like India. Cartridge-Based Nucleic Acid Amplification Test (CBNAAT) has emerged as a rapid and sensitive diagnostic tool.
Objective: To evaluate the diagnostic utility of CBNAAT in smear-negative pulmonary tuberculosis patients.
Methods: A prospective observational study was conducted on 400 suspected smear-negative PTB patients at Sheikh Bhikhari Medical College, Hazaribagh, Jharkhand, India, from January 2025 to December 2025. All patients underwent sputum smear microscopy and CBNAAT testing. Diagnostic accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated using culture as reference.
Results: CBNAAT detected Mycobacterium tuberculosis in 110 (27.5%) cases. The sensitivity and specificity were 87.5% and 98.2%, respectively. The positive predictive value was 95.5% and the negative predictive value was 94.8%. Rifampicin resistance was detected in 10.9% of CBNAAT-positive cases.
Conclusion: CBNAAT demonstrates high diagnostic accuracy in smear-negative PTB and significantly improves early detection and drug resistance identification.