Background: Testing asymptomatic contacts of confirmed COVID-19 cases for the presence of SARS-CoV-2 could reduce onward transmission by improving case ascertainment and lessen the impact of self-isolation on un-infected individuals . This study investigated the feasibility and acceptability of implementing a test to enable approach as part of England's tracing strategy .
Methods: Contacts of confirmed COVID-19 cases were offered serial testing as an alternative to self-isolation using daily self-performed lateral flow device (LFD) tests for the first 7 days post exposure . Asymptomatic participants with a negative LFD result were given 24 hours of freedom from self-isolation between each test . A self-collected confirmatory PCR test was performed on testing positive or at the end of the LFD testing period .
Results: Of 1,760 contacts , 882 consented to daily testing, with 812 within 48 hours of exposure sent testing packs . Of those who declined to participate , 39.1% stated they had already accessed PCR testing . Of the 812 who were sent packs , 570 (70.2 %) reported one or more LFD results; 102 (17.9 %) tested positive . Concordance between reported LFD result and a supplied LFD image was 97.1% . 82.8% of PCR positive samples and 99.6% of PCR negative samples were correctly detected by LFD . The proportion of secondary cases from contacts of those who participated in the study and tested positive (6.3% ; 95% CI : 3.4-11.1 %) were comparable to a comparator group who self-isolated (7.6% ; 95% CI : 7.3-7.8 %). Conclusion: This study shows a high acceptability, compliance and positivity rates when using self-administered LFDs among contacts of confirmed COVID-19 cases . Offering routine testing as a structured part of the contact tracing process is likely to be an effective method of case ascertainment.