Real-time polymerase chain reaction as an alternative method for diagnosis of multidrug-resistant tuberculosis: can it stand alone in this concern

Abstract

Background: Delays in diagnosing multidrug-resistant tuberculosis (MDR-TB) are responsible for higher tuberculosis morbidity and mortality and its subsequent transmission. Molecular assays such as real-time PCR (RT-PCR) used to identify drug resistance in Mycobacterium tuberculosis are more rapid than standard drug susceptibility testing. Objectives: The aim of this study was to evaluate the diagnostic performance of the Anyplex MTB/MDR RT-PCR assay in detecting MDR-TB strains. Patients and methods: Sputum samples were collected from 29 patients with symptoms and radiological findings suggestive of active pulmonary tuberculosis, with at least one of three sputum smear samples showing acid-fast bacilli and/ or sputum culture isolates positive for M. tuberculosis. The results obtained by RT-PCR were compared with those obtained by the Mycobacterium growth indicator tube SIRE method. Results: M. tuberculosis was confirmed in 29 specimens. Only six cases determined as MDR-TB were obtained by Mycobacterium growth indicator tube SIRE. For detection of rifampicin-resistant and isoniazid-resistant strains, the RT-PCR assay yielded a sensitivity of 62.5 and 66.66% and specificity of 80 and 95%, respectively. The overall sensitivity of that assay was 64.2% and specificity was 88.88%. Conclusion: RT-PCR is an easy and reliable assay for rapid detection of MDR-TB in clinical specimens. However, RT-PCR should be followed by a culture method to increase the overall sensitivity of that assay.