Rapid detection of Mycobacterium tuberculosis in pus samples of suspected cases of extrapulmonary tuberculosis by GeneXpert MTB/RIF assay and its comparison with conventional methods

Abstract

Introduction: GeneXpert MTB/RIF or cartridge-based nucleic acid amplification test is a rapid diagnostic tool used for the detection of Mycobacterium tuberculosis and its resistance to rifampicin. It can be offered as a first-line diagnostic modality in suspected cases of extrapulmonary tuberculosis (TB). This study was done to evaluate the diagnostic accuracy of the Xpert MTB/RIF assay for the detection of M. tuberculosis in extrapulmonary specimens and its resistance to rifampicin.Materials and Methods: This study was done in the Department of Microbiology at Indira Gandhi Institute of Medical Sciences, Patna, Bihar, over a period 18 months from January 2018 to June 2019 in 508 patients. The analysis and interpretation of the data were performed using Microsoft excel. The quantitative data obtained were expressed as percentage in tabular form.Results: Out of a total of 508 pus samples in suspected extrapulmonary TB patients, the percentage of males was more than females with male-to-female ratio being 1.6:1. Among the testing of Mycobacterium tuberculosis by various methods, maximum detection was done by Xpert MTB/RIF assay in 37% of cases. The least number of cases were detected by Ziehl–Neelsen staining (8.1%). Rifampicin resistance was detected in 14.9% of cases (28/188) while its resistance was not detected in 85.1% of cases (160/188) among cases of M. tuberculosis detected. Many of the negative samples on fluorescent and Ziehl–Neelsen staining came to be positive with GeneXpert testing assuring the sensitivity and specificity of Xpert MTB/RIF assay.Conclusion: In today's era when we are going for TB elimination, not only rapid TB case detection but also the early determination of multidrug resistance status is of prime value. This will not only assist in the identification of the patient with disease and drug resistance but also initiate prompt early intervention and treatment and moving a step closer in achieving the goal of TB elimination.