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

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.