• 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 21; 42 (2): 9810498-104.

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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