• Rahul Batra, Edward Blandford, Raghavendran Kulasegaran-Shylini, Matthias E Futschik, Abbie Bown, Matthew Catton, Hermione Conti-Frith, Alexandra Alexandridou, Rebecca Gill, Clara Milroy, Sean Harper, Holly Gettings, Maryann Noronha, Hooi-Ling Harrison, Sam Douthwaite, Gaia Nebbia, Paul E Klapper, Sarah Tunkel, Richard Vipond, Susan Hopkins, and Tom Fowler.
• Department of Infectious Diseases, St Thomas' Hospital, London, UK cidr-noe@gstt.nhs.uk.
• Emerg Med J. 2025 Jan 14.

BackgroundRapid identification of individuals with acute respiratory infections is crucial for preventing nosocomial infections. For rapid diagnosis, especially in EDs, lateral flow devices (LFDs) are a convenient, inexpensive option with a rapid turnaround. Several 'multiplex' LFDs (M-LFDs) now exist, testing for multiple pathogens from a single swab sample. We evaluated the real-world performance of M-LFD versus PCR testing in detecting influenza A, B and SARS-CoV-2) in the ED setting.MethodsAfter preliminary evaluation of an M-LFD (SureScreen) with laboratory-grown virus and PCR-negative clinical samples, it was evaluated in a real-world setting at the ED of St Thomas' Hospital (London, UK) from 1 December 2022 to 21 April 2023. Eligible participants were ≥18 years of age, admitted with respiratory symptoms and received concurrent M-LFD and PCR tests. Main endpoints were sensitivity to detect influenza A/B (primary) and SARS-CoV-2 (secondary) versus PCR. The probability of a true positive in relation to viral concentration (expressed as PCR cycle threshold (Ct)) was analysed using logistic regression.ResultsIn total, 808 symptomatic participants were included (49.8% female; mean age 46.9 years). Test sensitivity (95% CI) was 67.0% (56.9% to 76.1%) for influenza A (n=100), 94.1% (71.3% to 99.9%) for influenza B (n=17) and 48.2% (39.7% to 56.8%) for SARS-CoV-2 (n=141). Sensitivity for SARS-CoV-2 was significantly lower than that for influenza A and B (p=0.0057 and p=0.00088, respectively). The probability of a true positive was 98% for Ct<25 for influenza A and SARS-CoV-2 (influenza B non-evaluable). No co-infections were identified by PCR or M-LFD.ConclusionThe real-world performance of SureScreen M-LFD was consistent with laboratory evaluation and achieved a high sensitivity for individuals with high viral concentration, most likely to be infectious. Given the representative UK population sample, results could be generalised for use in other settings.© Author(s) (or their employer(s)) 2025. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ Group.

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