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

Abstract

Introduction. Evidence suggests that although people modify their behaviours, full adherence to self-isolation guidance in England may be suboptimal, which may have a detrimental impact on COVID-19 transmission rates.Hypothesis. 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.Aim. This study investigated the feasibility and acceptability of implementing a 'test to enable approach' as part of England's tracing strategy.Methodology. 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 h 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 1760 contacts, 882 consented to daily testing, of whom 812 individuals were within 48 h of exposure and were sent LFD testing packs. Of those who declined to participate, 39.1% stated they had already accessed PCR testing. Of the 812 who were sent LFD 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%. In total, 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%) was 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.

Keywords: COVID-19; DCT; SARS-CoV-2; contacts; lateral flow testing; testing.