Summary

Introduction: The aim of this study was to evaluate the performance of the Xpert MTB/RIF test in the diagnosis of M. tuberculosis in pulmonary and extrapulmonary clinical specimens with positive or negative smears.
Materials and Methods: Between January 2018 and December 2021, a total of 2082 samples were examined, including 1526 respiratory samples and 556 non-respiratory samples. The samples processed for culture were inoculated into Lowenstein Jensen (LJ) medium and Mycobacteria Growth Indicator Tube (MGIT) tubes, then MGITs were loaded into the MGIT 960 automated system. The Xpert MTB/RIF molecular test was performed to all samples according to the manufacturer's recommendations.
Results: M. tuberculosis was grown in culture in 153 (7,3%) of all samples, and the Xpert MTB/RIF test was positive in 203 (9,7%). ARB, MTB/RIF test and culture positivity in lung samples are; 86 (5,6%), 175 (11,4%) and 129 (8,4%), respectively.  ​In extrapulmonary samples; the positivity was 7 (1,2%), 28 (5%) and 24 (4,3%). When mycobacterial culture results are accepted as reference, the sensitivity was 53,6% and the specificity was 99,4% for the EZN staining method. For respiratory samples, these values ​​were 58,1% and 99,2%; for extrapulmonary samples, sensitivity and specificity were 29,2% and 100%, respectively. For all the samples examined with The Xpert MTB/RIF test; sensitivity, specificity; positive predictive value (PPV); and negative predictive value (NPV) were calculated as 89,5%, 96,6%, 67,5% and 99,1%, respectively.
Conclusion:  The sensitivity and specificity rates of the Xpert MTB/RIF test used in this study in non-respiratory samples were found to be slightly lower than in respiratory samples. It had high sensitivity and specificity rates in both sample groups. It was observed that The Xpert MTB/RIF test was a very fast and requiring low workload.