Applicability of Xpert MTB/RIF assay for routine diagnosis of tuberculosis: a four-year single-center experience

The aim of this study is to assess the Xpert MTB/RIF assay for diagnosis of the Mycobacterium tuberculosis complex in clinical samples and to compare the results by reference to the diagnostic method, Bactec MGIT 960.

A total of 7407 samples were included from patients not primarily suggesting pulmonary or extrapulmonary tuberculosis (TB), collected from patients required to be screened for TB and excluding TB diagnoses since it was a differential diagnosis. Also included were a total of 411 samples from patients primarily suggesting pulmonary or extrapulmonary TB.

In the first group, 152 of 7407 samples yielded positive results with the Bactec MGIT 960, 131 (1.77%) were found positive with Löwenstein-Jensen medium, and 295 (3.99%) were found positive with Ziehl-Neelsen staining. In the second group, 24 (5.8%), 17 (4.1%), and 28 (6.8%) of 411 samples were found positive. Xpert MTB/RIF [27 (6.6%) of 411 samples] detected 3 additional samples as positive, and these 3 cases were clinically compatible with TB.

The Xpert MTB/RIF assay shows superior performance for the diagnosis of TB. Its usefulness in culture-negative patients and the best method for integrating this diagnostic method into current tuberculosis diagnostic algorithms both need further study.