Abstract
BackgroundEntry screening tends to start with a search for febrile international passengers, and infrared thermoscanners have been employed for fever screening in Japan. We aimed to retrospectively assess the feasibility of detecting influenza cases based on fever screening as a sole measure.MethodsTwo datasets were collected at Narita International Airport during the 2009 pandemic. The first contained confirmed influenza cases (n = 16) whose diagnosis took place at the airport during the early stages of the pandemic, and the second contained a selected and suspected fraction of passengers (self-reported or detected by an infrared thermoscanner; n = 1,049) screened from September 2009 to January 2010. The sensitivity of fever (38.0°C) for detecting H1N1-2009 was estimated, and the diagnostic performances of the infrared thermoscanners in detecting hyperthermia at cut-off levels of 37.5°C, 38.0°C and 38.5°C were also estimated.ResultsThe sensitivity of fever for detecting H1N1-2009 cases upon arrival was estimated to be 22.2% (95% confidence interval: 0, 55.6) among nine confirmed H1N1-2009 cases, and 55.6% of the H1N1-2009 cases were under antipyretic medications upon arrival. The sensitivity and specificity of the infrared thermoscanners in detecting hyperthermia ranged from 50.8-70.4% and 63.6-81.7%, respectively. The positive predictive value appeared to be as low as 37.3-68.0%.ConclusionsThe sensitivity of entry screening is a product of the sensitivity of fever for detecting influenza cases and the sensitivity of the infrared thermoscanners in detecting fever. Given the additional presence of confounding factors and unrestricted medications among passengers, reliance on fever alone is unlikely to be feasible as an entry screening measure.
Highlights
Entry screening tends to start with a search for febrile international passengers, and infrared thermoscanners have been employed for fever screening in Japan
Because of the relatively high sensitivity and specificity, the negative predictive value (NPV) of infrared thermoscanners in excluding non-febrile passengers is believed to be high [15,16,17,18,19], which supports the use of infrared thermoscanners for releasing negative individuals, under an important assumption that the prevalence of infected individuals is small among the total number of passengers and with the expectation that “cases” are represented as febrile passengers
Considering the total passengers arriving at Narita International Airport, the actual positive predictive value (PPV) will be smaller than our estimates, implying more false-positive passengers during mass screening if one relies on infrared thermoscanners for active detection of hyperthermia [21]
Summary
Entry screening tends to start with a search for febrile international passengers, and infrared thermoscanners have been employed for fever screening in Japan. Since the diagnostic criteria and definitions of both SARS and influenza-like illness include fever, entry screening tends to start with a search for febrile international passengers, and such fever screening has tended to largely rely on the use of infrared thermoscanners because of their non-invasive nature and the need to screen massive numbers of travelers at the border [12,13,14]. Despite the high diagnostic accuracy and NPV under the above-mentioned assumption and expectation, the readings of infrared thermoscanners are known to be influenced by several confounding factors including age and outdoor temperature, and the small positive predictive value (PPV) with the small prevalence of febrile passengers is not believed to realistically permit less strict entry screening (e.g. use of infrared thermoscanners to actively detect hyperthermia) [20,21,22]. The validity of fever screening in relation to its theoretical rationale (e.g. the above-mentioned assumption and expectation) should be assessed in practical settings
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
