Initial experience with GeneXpert MTB/RIF assay in the Arkansas Tuberculosis Control Program

Background: Mycobacterium tuberculosis remains one of the most significant causes of death from an infectious agent. Rapid and accurate diagnosis of pulmonary and extra-pulmonary tuberculosis (TB) is still a great challenge. The GeneXpert MTB/RIF assay is a novel integrated diagnostic system for the diagnosis of tuberculosis and rapid detection of Rifampin (RIF) resistance in clinical specimens. In 2012, the Arkansas Tuberculosis Control Program introduced GeneXpert MTB/RIF assay to replace the labour-intensive Mycobacterium Tuberculosis Direct (MTD) assay.

Aims: To rapidly diagnose TB within two hours and to simultaneously detect RIF resistance.

Objectives: Describe the procedure used to introduce GeneXpert MTB/RIF assay in the Arkansas Tuberculosis Control Program.Characterise the current gap in rapid M. tuberculosis diagnosis in Arkansas.Assess factors that predict acid fast bacilli (AFB) smearnegative but culture-positive cases in Arkansas.Illustrate, with two case reports, the role of GeneXpert MTB/RIF assay in reduction of time to confirmation of M. tuberculosis diagnosis in the first year of implementation.

Method: Between June 2012 and June 2013, all AFB sputum smearpositive cases and any others, on request by the physician, had GeneXpert MTB/RIF assay performed as well as traditional M. tuberculosis culture and susceptibilities using Mycobacteria Growth Indicator Tube (MGIT) 960 and Löwenstein-Jensen (LJ) slants. Surveillance data for January 2009-June 2013 was analysed to characterise sputum smear-negative but culture-positive cases.

Results: Seventy-one TB cases were reported from June 2012- June 2013. GeneXpert MTB/RIF assay identified all culture-positive cases as well as three cases that were negative on culture. Also, this rapid assay identified all six smear-negative but M. tuberculosis culture-positive cases; two of these cases are described as case reports.

Conclusion: GeneXpert MTB/RIF assay has made rapid TB diagnosis possible, with tremendous potential in determining isolation of TB suspects on one hand, and quickly ruling out TB whenever suspected.