ABSTRACT
PURPOSE: Rapid antigen test (RAT) is used to screen influenza rapidly. The clinical sensitivity of RAT was poor for 2009 H1N1 influenza. The aim of this study was to identify the correlation of time gap (TG) between fever onset and the sensitivity of RAT for 2009 H1N1 influenza. METHODS: Data were collected retrospectively during the pandemic H1N1 2009 influenza season between October 2009 and February 2010. The RAT was done by using SD Bioline influenza antigen (Standard Diagnostics Inc.) in nasopharyngeal swab. The 2009 H1N1 influenza was confirmed by real-time reverse transcriptase polymerase chain reaction (rRT-PCR). Specimens were categorized according to the TG between fever onset and performance of RAT. They were classified into 120 hours (TG6). RESULTS: The overall sensitivity of RAT was 69.9%. The TG dependent sensitivity of RAT at TG1, TG2, TG3, TG4, TG5, and TG6 was 64.3%, 73.3%, 61.1%, 88.9%, 83.3%, and 61.1% respectively. The sensitivity of RAT was the highest when the TG was 72 to 96 hours. But this result was not statistically significant. CONCLUSION: Correlation of TG between fever onset and the sensitivity of RAT for 2009 H1N1 influenza was not statistically significant. But our study suggested that 72 to 96 hours after fever onset is the most sensitive time of RAT. Timely optimal performance of the RAT could have a significant impact on improving results. Further evaluation for better sensitivity would be needed.