Estimating LFT and qPCR test-sensitivity over time since infection from a human challenge study

Abstract

AbstractTesting has been central to global policy throughout the SARS-CoV-2 pandemic. Understanding how test sensitivity changes after exposure is crucial for the interpretation of test outcomes and the design of testing-based interventions. Using data from a human challenge study, we derive temporal test sensitivity profiles for lateral flow tests (LFT), quantitative polymerase chain reaction (qPCR) tests and viable virus, measured by focus-forming assay (FFA). The median time to detectability was 2 days (throat swab) and 3 days (nasal) for qPCR and 4 days for LFT (both swabs), and there was strong positive correlation between first LFT positive and first FFA positive for both throat (p=0.00019) and nasal (p=0.00032) swabs, supporting the use of LFTs as a method of detecting infectiousness. Peak LFT sensitivity was 82.4% (67.0%-91.8%) for throat samples, occurring 6 days post-exposure and 93.3% (85.1%-98.0%) for nasal, 7 days post-exposure. These temporal profiles provide quantification of the mean behaviour of these tests and individual-based variability and could inform a framework for investigating future testing-based interventions.