Laboratory Evaluation of the Xpert Xpress Flu/RSV Test in Hubei, China

Early confirmation of infections with influenza virus and/or respiratory syncytial virus (RSV) is beneficial for prompt treatment and outbreak management. This study aimed to assess the Cepheid Xpert Xpress Flu/ RSV assay in Central China, using Sanger sequencing as the reference method.

Nasopharyngeal swab (NP) samples from pediatric and adult patients with influenza-like illnesses were collected by the Hubei Province Disease Control and Prevention Center. The Xpert Xpress Flu/RSV assay was performed according to the manufacturer's guidelines, and the cycle threshold (Ct) values of each positive sample were recorded. Sanger sequencing was then performed on the NP samples, and discordant results were verified with a self-built fluorescent PCR method and virus tissue culture.

The Xpert assay demonstrated a sensitivity of 97.06%, a specificity of 95.81%, an accuracy of 95.93%, a PPV of 71.74%, and a negative predictive value (NPV) of 99.66% for influenza A (Flu A) detection. Influenza B (Flu B) detection had a sensitivity of 100%, a specificity of 88.52%, an accuracy of 91.86%, a PPV of 78.12%, and an NPV of 100%. RSV detection had a sensitivity of 100%, a specificity of 95.67%, an accuracy of 98.80%, a PPV of 60.00%, and an NPV of 100%. False positive samples had significantly higher mean Ct values compared to true positive samples for detecting Flu A, Flu B, or RSV (p < 0.001).

The Xpert Xpress Flu/RSV test is a rapid, accurate, and reliable molecular diagnostic method for Flu A, Flu B, and RSV. Positive Xpert results with a low Ct value are more likely to indicate a clinical infection with Flu/RSV to allow timely diagnosis and treatment.