The Abbott RealTime MTB assay and the Cepheid GeneXpert assay show comparable performance for the detection of Mycobacterium tuberculosis in sputum specimens

Abstract

Objectives: To evaluate the performance of the newly developed technology Abbott RealTime MTB assay (RealTime MTB assay) for the detection of Mycobacterium tuberculosis in sputum specimens and to compare its performance with that of the Cepheid GeneXpert assay.

Methods: Sputum specimens were collected from 270 subjects suspected to have tuberculosis (TB). Smear microscopy, culture, identification, RealTime MTB, and GeneXpert assays were performed according to standard protocols. Accuracy measures of the method evaluated were determined using solid culture as the reference standard.

Results: The RealTime MTB assay showed similar positive detection rates as the GeneXpert assay in smear-positive, culture-positive, and smear/culture-negative groups; no significant differences were found in these groups between the two assays. The RealTime MTB assay demonstrated a sensitivity of 100% and a specificity of 84.4%; the GeneXpert assay had a sensitivity of 96.9% and specificity of 89.6%. After the resolution of discordant results by PCR-based molecular method, the sensitivities and specificities of the RealTime MTB and GeneXpert assays were 100% vs. 97% and 90.0% vs. 95.6%, respectively; no significant difference in sensitivity or specificity was found between the RealTime MTB and GeneXpert assays.

Conclusions: This study demonstrated that the Abbott RealTime MTB and Cepheid GeneXpert assays have similar sensitivity and specificity. The Abbott RealTime MTB assay is a highly promising method for the diagnosis of TB.

Keywords: Abbott RealTime MTB assay; Cepheid GeneXpert assay; Culture; Mycobacterium tuberculosis; Performance.