Introduction: WHO End TB Strategy calls for the early diagnosis of TB and universal drug susceptibility testing (DST). Molecular assays based on nucleic acid amplification techniques such as polymerase chain reaction have been developed for rapid TB diagnosis and are being implemented in developing countries. CBNAAT is cartridge based nucleic acid amplification test an automated polymerase chain reaction test utilizing the GeneXpert platform.                   

Aim and Objectives: The study aims to determine the clinical utility of CBNAAT in the diagnosis of pulmonary TB in a tertiary care center.

Materials and Methods: 129 cases OF PRESUMPTIVE PTB CASES were included in the study after exclusion criteria. All patients were subjected to routine blood investigations and Sputum, BAL specimens for AFB smear, CBNAAT and liquid cultures. Results were analysed using SPSS software.

Results: Of the 129 cases males were 82 (63.5%), and females were 47(36.5%).

The sensitivity, specificity, PPV and NPV of all samples for AFB smear were 54.79%, 98.43%, 95.24% and 79.11% respectively. The sensitivity, specificity, PPV and NPV of all samples for CBNAAT were 84.93%, 92.13%, 86.11% and 91.41% respectively.

The sensitivity and specificity of smear positive, culture positive cases was (26/29) 96.30% and 100% with a positive predictive value 100% and negative predictive value of 66.67%. The sensitivity and specificity of smear negative culture positive cases was 70%, 92.5% respectively with a PPV of 70% and NPV of 92.5%.

Conclusions: CBNAAT has good clinical utility in smear negative culture positive cases both in pulmonary cases. CBNAAT has higher diagnostic efficacy than AFB smear in all pulmonary samples.

Keywords: Pulmonary Tuberculosis, Molecular Diagnostics, CBNAAT, Genexpert

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Dr Thammana Sridevi

Door. No. 6-15-46/3, B-2, Sea Winds Apartments, East Point Colony, Visakhapatnam – 530017,

Andhra Pradesh, India