Performance of six influenza rapid tests in detecting human influenza in clinical specimens.

BACKGROUND: The rapid diagnosis of influenza can alter the management of a patient's illness, resulting in reduced antibiotic usage, correct use of influenza antivirals and reduced length of stay in hospital emergency departments. The rapid tests have also been used to detect outbreaks in institutions and may play a role in pandemic influenza control. OBJECTIVES: To test six different rapid influenza tests, in a head-to-head comparison for the detection of seasonal influenza types A and B, compared to laboratory-based tests. STUDY DESIGN: One hundred and seventy-seven clinical specimens taken from mostly paediatric patients between June and October 2006 were tested using six influenza diagnostic tests and three laboratory-based techniques (immunofluorescence, cell culture and real-time RT-PCR). RESULTS AND CONCLUSION: Compared with cell culture, five of the rapid tests (Binax Now Influenza A&B, Directigen EZ Flu A+B, Denka Seiken Quick Ex-Flu, Fujirebio Espline Influenza A&B-N, and Quidel QuickVue Influenza A+B Test) demonstrated a similar influenza A sensitivity of between 67-71% and a specificity of 99-100%, however one rapid test (Rockeby Influenza A Antigen Test) had a significantly lower influenza A sensitivity of only 10% (specificity was 100%). For the five kits that detected influenza B antigen, sensitivity was considerably lower than that seen for influenza A (sensitivity for all the kits was 30%), although the number of specimens containing influenza B viruses was low.