A Novel Olfactory Self-Test Effectively Screens for COVID-19

Key to curtailing the COVID-19 pandemic are wide-scale testing strategies 1,2 . An ideal test is one that would not rely on transporting, distributing, and collecting physical specimens. Given the olfactory impairment associated with COVID-19 3-7 , we developed a novel measure of olfactory perception that relies on smelling household odorants and rating them online. We tested the performance of this real-time tool in 12,020 participants from 134 countries who provided 171,500 perceptual ratings of 60 different household odorants. We observed that olfactory ratings were indicative of COVID-19 status in a country, significantly correlating with national infection rates over time. More importantly, we observed remarkable indicative power at the individual level (90% sensitivity and 80% specificity). Critically, olfactory testing remained highly effective in participants with COVID-19 but without symptoms, and in participants with symptoms but without COVID-19. In this, the current odorant-based olfactory test stands apart from symptom-checkers (including olfactory symptom-checkers) 3 , and even from antigen tests 8 , to potentially provide a first line of screening that can help halt disease progression at the population level.