Diagnostic performance of multiplex lateral flow tests in ambulatory patients with acute respiratory illness

Background We assessed the performance of three different multiplex lateral flow assays which provide results for influenza, respiratory syncytial virus (RSV) and SARS-CoV-2. Methods Ambulatory patients 6 months and older presenting with two or more symptoms or signs of an acute respiratory illness were enrolled in an outpatient clinic in Hong Kong. Multiplex lateral flow tests manufactured by SureScreen, Microprofit and Goldsite were performed by trained research staff using the nasal swabs from each test kit, and separate swabs were collected for RT-PCR testing. Results Between 4 April and 20 October 2023, 1646 patients were enrolled and tested by at least one lateral flow test. The point estimates for all three multiplex tests had high sensitivity above 80% for influenza A and SARS-CoV-2, and the tests manufactured by Microprofit and Goldsite had sensitivity exceeding 84% to detect RSV. Test sensitivity increased with viral load. Specificity was higher than 97% for all three tests except for the SureScreen test which had specificity 86.2% (95% CI: 83.9% to 88.3%) for influenza A. Conclusions The multiplex lateral flow tests provided timely diagnosis of influenza, RSV and SARS-CoV-2 infection and can be used to inform clinical management and infection control such as isolation behaviours. ### Competing Interest Statement BJC consults for AstraZeneca, Fosun Pharma, GSK, Haleon, Moderna, Novavax, Pfizer, Roche, and Sanofi Pasteur. The authors report no other potential conflicts of interest. ### Funding Statement This research was supported by the Health and Medical Research Fund, Health Bureau, The Government of the Hong Kong Special Administrative Region (grant no. INF-HKU-3). BJC is supported by the Theme-based Research Scheme (Project No. T11-712/19-N) of the Research Grants Council of the Hong Kong SAR Government. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The study protocol was approved by the Institutional Review Board of the University of Hong Kong. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present work are contained in the manuscript