Performance of laboratory diagnostics for the detection of influenza A(H1N1)v virus as correlated with the time after symptom onset and viral load

Background: To diagnose influenza A(H1N1)v virus infection, accurate and rapid detection are important. However, there is scanty data on the performance of various laboratory diagnostics. Objective: To compare the performance of rapid antigen test (RAT), viral culture and RT-PCR for the detection of influenza A(H1N1) v virus and to correlate their performance with the time after symptom onset and viral load. Study Design: From May 1, 2009 to June 25, 2009, respiratory samples were collected from 5740 individuals suspected of having influenza A(H1N1) v infection. The performance of viral culture and RT-PCR were investigated and correlated with the time after symptom onset. The sensitivity of RAT ESPLINE influenza A & B-N (Fujirebio Inc, Tokyo) was evaluated using a subset of 60 samples from patients diagnosed as having influenza A(H1N1) v infection. Results: Using respiratory samples from 587 patients diagnosed with influenza A(H1N1) v infection, comparison of laboratory diagnostics showed viral culture and RT-PCR gave comparable results with overall sensitivity of 93.9% and 98.1%, respectively. For RAT, when testing a subset of 60 samples collected <= 3 days following symptom onset, the sensitivity was 62%. Conclusions: Although viral shedding is prolonged and of higher titre in influenza A(H1N1) v infection, RAT showed a low sensitivity of 62% among patients presenting <= 3 days after symptom onset. Viral culture showed comparable performance with RT-PCR and with sensitivity better than that documented for seasonal influenza. (C) 2009 Elsevier B. V. All rights reserved.