Head-to-Head Comparison between Xpert MTB/RIF Assay and Real-Time Polymerase Chain Reaction Assay Using Bronchial Washing Specimens for Tuberculosis Diagnosis

Abstract

Background: With the introduction of Xpert MTB/RIF assay (Xpert), its incorporation into tuberculosis (TB) diagnostic algorithm has become an important issue. The aim of this study was to evaluate the performance of the Xpert assay in comparison with a commercial polymerase chain reaction (PCR) assay.Methods: Medical records of patients having results of both Xpert and AdvanSure TB/NTM real-time PCR (AdvanSure) assays using the same bronchial washing specimens were retrospectively reviewed.Results: Of the 1,297 patients included in this study, 205 (15.8%) were diagnosed with pulmonary TB. Using mycobacterial culture as the reference method, sensitivity of the Xpert assay using smear-positive specimens was 97.5%, which was comparable to that of the AdvanSure assay (96.3%, p=0.193). However, the sensitivity of the Xpert assay using smear-negative specimens was 70.6%, which was significantly higher than that of the AdvanSure assay (52.9%, p=0.018). Usng phenotypic drug susceptibility testing as the reference method, sensitivity and specificity for detecting rifampicin resistance were 100% and 99.1%, respectively. Moreover, a median turnaround time of the Xpert assay was 1 day, which was significantly shorter than 3 days of the AdvanSure assay (p<0.001).Conclusion: In comparison with the AdvanSure assay, the Xpert assay had a higher sensitivity using smear-negative specimens, a shorter turnaround time, and could reliably predict rifampin resistance. Therefore, the Xpert assay might be preferentially recommended over TB-PCR in Korean TB diagnostic algorithm.

Performance of the BD MAX MDR-TB assay in a clinical setting and its impact on the clinical course of patients with pulmonary tuberculosis: a retrospective before-after study

“…Our results indicate that the sensitivity of BD MAX in the PTB diagnosis is superior to that of the AFB smear and AdvanSure TB-PCR. Previously, the diagnostic accuracy of Xpert using unprocessed specimens has been reported to be more sensitive than that of the AdvanSure TB-PCR method using decontaminated and concentrated specimens, especially using lower respiratory tract specimens (LRTS), which are more sterile and concentrated than sputum specimens [ 20 , 21 ]. Moreover, although our study excluded patients with negative AFB culture results but clinically diagnosed PTB, previous studies showed enhanced diagnostic usefulness of Xpert for AFB culture-negative LRTS [ 22 , 23 ].…”

Rapid Detection of Mycobacterium Tuberculosis Using a Novel Point-of-Care BZ TB/NTM NALF Assay: Integrating LAMP and LFIA Technologies

“…The Xpert has the advantage of detecting RIF resistance, as well as high sensitivity and specificity in comparison with the AFB microscopy [ 32 ]. Compared with the AdvanSure TB/NTM RT-PCR, the Xpert provided better sensitivity, especially in AFB smear–negative cases [ 33 , 34 ]. However, the actual use of the Xpert is limited in high-burden countries with limited resources.…”

Bronchoscopic Strategies to Improve Diagnostic Yield in Pulmonary Tuberculosis Patients

“…Although conventional TB-PCR and the Xpert MTB/RIF assay theoretically have similar diagnostic accuracies, the Xpert MTB/RIF assay often has higher sensitivity in clinical settings. This difference is based on the Xpert MTB/RIF assay’s direct utilization of sputum specimens without preprocessing; conventional TB-PCR may lose TB bacilli during preprocessing steps, such as decontamination or concentration, especially in patients with a low-TB burden [ 26 ]. Similarly, the use of the Xpert MTB/RIF assay for bronchoscopic specimens may be able to overcome the limitations of conventional TB-PCR, potentially enhancing diagnostic accuracy.…”