The acceptability of testing contacts of confirmed COVID-19 cases using serial, self-administered lateral flow devices as an alternative to self-isolation

Love, N. K.; Ready, D.; Turner, C.; Yardley, L.; Rubin, G. J.; Hopkins, S.; Oliver, I.

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.