Comparison of the Cepheid Xpert Xpress Flu/RSV assay and commercial real-time PCR for the detection of influenza A and influenza B in a prospective cohort from China

Background: The Xpert Xpress Flu/RSV assay is released by FDA for rapid detection of influenza A (FluA), influenza B (FluB), and respiratory syncytial virus (RSV). This study aimed to evaluate its clinical performance in comparison to that of the RT-PCR assay cleared by China FDA (CFDA-PCR). Methods: Nasopharyngeal specimens were collected from patients and tested by the two assays side by side. Discordant results were tested with a laboratory-developed real-time PCR for resolution. Viral load in the sample was quantified with a droplet digital PCR. Results: A total of 658 specimens were involved and gave 94.7%-99.1% agreement between the two assays. The Xpert assay showed higher sensitivity for FluA (100% vs. 89.8%) and FluB detection (100% vs. 95.3%), and also higher accuracy (98.9% vs. 95.7%) for FluA than the CDFA-PCR. The positive and negative predictive values (NPV) for the three viruses ranged from 90.5% to 100% in the two assays, with higher NPV for FluA and FluB in Xpert assay. Moreover, the Xpert Ct values showed a linear correlation with virus titer in specimens tested. Conclusion: Overall, the Xpert assay is a reliable and sensitive tool for the detection of FluA, FluB and RSV in our clinical settings. (c) 2019 The Authors. Published by Elsevier Ltd on behalf of International Society for Infectious Diseases. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).