Sensitivity Assessment of Rapid Influenza Diagnostic Tests for the Detection of the 2009 Pandemic Influenza A (H1N1) Virus in Clinical Specimens

Background Influenza antigen detection test kits can provide results in 30 minutes and are used frequently for the detection of seasonal influenza infections It is very important to determine the efficacy of these tests in the diagnosis of the 2009 pandemic influenza A (H1N1) virus due to the global spread of this new influenza virus Methods We evaluated 4 rapid influenza diagnostic tests (Binax Now Influenza A&B, BD Directigen EZ Flu A+B Fujirebio Espline Influenza A&B N, and BioTracer Influenza A&B Test) for their ability to detect the 2009 pandemic influenza A (H1N1) virus and compared these results with the diagnostic sensitivity obtained following real time polymerase chain reaction (PCR) analysis of the same samples Results Reverse transcriptase polymerase (hain reaction (RI PCR) analysis of 252 specimens identified 176 influenza A (H1N1) positive samples Of these between 29 and 62 also tested positive using the 4 rapid tests examined, demonstrating the sensitivity of the respective tests was 16 5% 35 2% with specificities of 100% However the 4 rapid tests were 77 3% 100% sensitive when samples contained high influenza A (H1N1) virus titers suggesting the sensitivity of these detection kits was dependent on viral loads Finally the sensitivity of the 4 detection kits tested was higher when samples from children were examined compared with samples from adults Conclusions Data presented in this report indicated the sensitivity of the respective influenza antigen detection test kits examined was low compared to the sensitivity observed following RI PCR Nonetheless they are useful tools during early outbreak investigations of influenza like illnesses particularly in the screening of critically ill patients and pediatric patients However negative results could be confirmed using other tests (eg AT PCR if necessary)