2014, Cilt 44, Sayı 2, Sayfa(lar) 061-064 |
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Evaluation of GeneXpert MTB/RIF Assay for the Diagnosis of Tuberculosis and Rapid Detection of Rifampicin Resistance in Clinical Specimens |
Cengiz ÇAVUŞOĞLU, Mehmet SOYLU |
Ege Üniversitesi Tıp Fakültesi, Tıbbi Mikrobiyoloji Anabilim Dalı |
Keywords: Gene Xpert MTB/RIF, rapid diagnosis, Mycobacterium tuberculosis, rifampicin resistance |
Objective: The Gene Xpert MTB/RIF assay (Cepheid, Sunnyvale, California, USA) is a novel integrated diagnostic device that performs sample processing and semi-nested real-time PCR analysis in a single hands-free step for the diagnosis of tuberculosis and rapid detection of rifampicin (RIF) resistance in clinical specimens. The aim of this study was to determine the sensitivity and specificity of the GeneXpert MTB/RIF assay for the diagnosis of tuberculosis and rapid detection of RIF resistance in smear-positive and smear-negative respiratory and non-respiratory clinical specimens.
Materials and Methods: In this study, 633 respiratory and 608 non-respiratory specimens analyzed in the Mycobacteriology laboratory of Medical Microbiology Department, Ege University Medical Faculty, Izmir, Turkey, were evaluated. All samples were inoculated onto Löwenstein-Jensen medium and MGIT 960 (Becton Dickinson Microbiology System, Sparks, NV, USA). GenoType MTBDR plus (Hain Lifescience GmbH) was used for identification of isolates. Antimicrobial susceptibilities of Mycobacterium tuberculosis complex were tested using MGIT960. Manufacturer recommendations were used for GeneXpert MTB/RIF (Cepheid, Sunnyvale, CA) test.
Results: The GeneXpert MTB/RIF was evaluated for the diagnosis of tuberculosis and rapid detection of RIF resistance in 633 respiratory specimens and 608 non-respiratory specimens. Of the 633 respiratory specimens examined, 48 were culture positive for M. tuberculosis. When all the respiratory samples were evaluated the sensitivity and specificity of the test were 93.8 and 98.8, respectively. For 30 specimens with smear-positive results and 18 specimens with smear-negative results, the sensitivity of the test was 100 and 83.3%, respectively. Of the 608 non-respiratory specimens examined, 32 were culture positive for M. tuberculosis. The sensitivity and specificity of the test were 71.9 and 99.3, respectively. For 12 specimens with smear-positive results and 20 specimens with smear-negative results, the sensitivities were 100 and 55%, respectively. The GeneXpert MTB/RIF assay detected four RIF-resistant specimens and 76 RIF-susceptible specimens, and the results were confirmed by drug susceptibility tests (DST).
Conclusion: The GeneXpert MTB/RIF test could be a useful tool for the rapid identification of RIF-resistant M. tuberculosis, especially in smear-positive clinical samples and smear-negative respiratory samples. However the test results must always be confirmed by culture and DST.
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