Evaluation of GeneNAT Real-Time Polymerase Chain Reaction Analyzer and Pre-loaded Chip-Based Mycobacterium tuberculosis and Multidrug-Resistant Tuberculosis Detection in the Diagnosis of Pulmonary Tuberculosis

Background: Tuberculosis (TB) is still the second causative agent of death worldwide after COVID-19. It is caused by Mycobacterium tuberculosis (MTB) infection. Objective: The aim of the current study was to compare the performance of GeneNAT real-time polymerase chain reaction analyzer and pre-loaded chip-based MTB screening and multidrug-resistant tuberculosis (MDR-TB) detection kit (Smart Sure^{TM} MTB & MDR-TB, Genetix Biotech Asia Pvt. Ltd., New Delhi, India) against the established WHO-approved GeneXpert Ultra (MTB/rifampicin (RIF)), line probe assay (LPA), and mycobacteria growth indicator tube (MGIT) culture at point of care (POC) level. Methods: A total of 450 pulmonary TB (PTB) suspect patients were enrolled from October 2023 to March 2024 at the Intermediate Reference Laboratory, Department of Medicine, All India Institute of Medical Sciences, New Delhi, India. GeneXpert and GeneNAT tests were done directly from sputum specimens. However, processed sputum specimens were used for both LPA (GenoType MTBDRplus) and liquid culture and drug susceptibility testing (MGIT culture and drug susceptibility testing (DST)). Results: On comparing with GeneXpert, for the detection of MTB and rifampicin (RIF), Smart Sure^{TM} showed a sensitivity of 98.18% and 97.5% with a specificity of 100% and 98.92%, respectively. While comparing mutations in the  rpoB gene with LPA, the Smart Sure^{TM} MDR-TB kit exhibited sensitivity and specificity of 96.77% and 99.12%, respectively. For katG and inhA genes, sensitivity and specificity were 97.6% & 85.71% and 98.66% & 98.01%, respectively, for both genes. Smart Sure^{TM} MDR-TB showed comparable results with MGIT-DST with sensitivity and specificity of 96.88% & 96.15% and 98.99% & 99.02%, respectively, for both RIF and isoniazid (INH) drugs. Conclusion: The GeneNAT system test may provide the status of RIF and INH resistance in PTB cases in a short time with the use of minimal specimens. It required very little infrastructure with less skilled laboratory staff in comparison with other WHO-approved diagnostics used in resource-limited countries with TB and drug-resistant TB burdens.