Prospective evaluation of three rapid molecular tests for seasonal influenza in patients presenting at an emergency unit.

BACKGROUND: For infection control measures, rapid accurate diagnostics on admission of patients with suspected seasonal influenza is crucial.

OBJECTIVE: Prospective comparison of three rapid molecular tests for detection of influenza A/B RNA.

STUDY DESIGN: Outpatients presenting at the Medical emergency department of Graz University Hospital with influenza-like illness and a requirement for hospitalization (n = 312) were studied. Nasopharyngeal swabs were collected with the 3 mL-version of the UTM™ Viral Transport Medium (Copan). Specimens were tested for influenza A and B RNA using the Alere™ i Influenza A & B (Abbott), the cobas® Influenza A/B (Roche), and the Xpert® Xpress Flu/RSV (Cepheid) tests. Results were compared to those obtained from the same specimen by the Influenza A/B R-GENE® (bioMerieux) test based on real-time PCR as reference method.

RESULTS: Overall sensitivities of the Abbott, Roche, and Cepheid tests were 90.5%, 96.0%, and 97.0%, overall specificities 99.4%, 97.6%, and 98.2% respectively. With the Abbott and the Cepheid tests, all specimens gave valid results, while the Roche test showed invalid results in 37 (12.1%) specimens. Total time to result for the Abbott, Roche, and Cepheid tests was 18 min, 22 min, and 32 min respectively.

CONCLUSIONS: The Abbott test lacked sensitivity, the Roche test was impaired by a high number of invalid results. Overall, despite the longest total time to result, the Cepheid test showed the best performance to detect influenza virus RNA in symptomatic patients presenting at an emergency unit in this study.