A Comparative Study of Genexpert MTB/RIF Assay with Conventional AFB Smear for the Diagnosis of Suspected Cases of Pulmonary And Extrapulmonary Tuberculosis From a Tertiary Care Hospital, Greater Noida

Abstract

Introduction: Tuberculosis (TB) continues to pose a significant public health challenge worldwide, with high morbidity and mortality, particularly in low- and middle-income countries. Rapid and accurate detection of Mycobacterium tuberculosis (MTB) and drug resistance is essential for early treatment and control. This study aimed to evaluate the diagnostic utility of GeneXpert in comparison with Ziehl–Neelsen (ZN) smear microscopy and to assess rifampicin resistance in pulmonary and extrapulmonary samples.

Aim and Objective: Comparative study of GeneXpert MTB/RIF assay with conventional AFB smear for the diagnosis of suspected cases of Pulmonary and Extrapulmonary tuberculosis

Materials and Methods: A total of 1389 clinical samples were processed in the TB laboratory, of which 100 confirmed cases were included. Pulmonary (sputum, BAL) and extrapulmonary (pus, gastric aspirate, pleural fluid, CSF, ascitic fluid, tissue) specimens were examined. Preliminary identification was performed by ZN staining, and confirmation with rifampicin resistance detection was carried out using the GeneXpert MTB/RIF assay.

Results: Among the 100 patients, 60% were males and 40% females, with the majority (32%) in the 21–30 year age group. Pulmonary specimens accounted for 74% of cases, predominantly sputum (67%). Smear positivity was 92%, while GeneXpert detected MTB in 100% of cases, including 8 smear-negative samples. Rifampicin resistance was detected in 19% of cases—17.6% in pulmonary and 23.1% in extrapulmonary TB. A strong correlation was observed between smear grading and bacterial load by GeneXpert.

Conclusion: GeneXpert demonstrated superior sensitivity over smear microscopy and enabled rapid detection of rifampicin resistance. Its integration into routine diagnostics can enhance early case detection, guide timely treatment, and reduce TB transmission in high-burden settings.