Performance of Xpert MTB/RIF for detection of Mycobacterium tuberculosis and rifampicin resistance in pus aspirates

Abstract

Introduction: WHO endorsed Xpert MTB/RIF assay has proven to be rapid with results obtained within 2h. The evidence base regarding the use of Xpert MTB/RIF in pulmonary TB is strong. Relatively few performance data have been published to date on detection of Mycobacterium tuberculosis in aspirated pus specimens from abscesses.

Objectives: The aim of the study was to determine the sensitivity and specificity of Xpert MTB/RIF assay for the detection of M. tuberculosis and rifampicin resistance in aspirated pus specimens using culture on Lowenstein Jensen (LJ) medium and economic variant of proportion method (PM) for drug susceptibility testing (DST) as the reference standard.

Results: Xpert MTB/RIF assay in comparison to conventional reference method showed sensitivity and specificity of 76.19% and 68.75% for detection of M. tuberculosis and 71.4% and 100% for detection of rifampicin resistance respectively.

Conclusion: The simplicity, sensitivity, speed and automation makes this assay a very promising diagnostic test for detection of M. tuberculosis and rifampicin resistance in aspirated pus specimens.

Keywords: Extrapulmonary TB; GeneXpert; Pus.