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Quantitative Assessment of Olfactory Dysfunction Accurately Detects Asymptomatic COVID-19 Carriers
17 Pages Posted: 28 Jul 2020More...
BACKGROUND: COVID-19 threatens the global community, because a large fraction of infected people are asymptomatic, yet can effectively transmit SARS-CoV-2. Finding and isolating these silent carriers is a crucial step in confining the spread of the disease. A sudden loss of the sense of smell (anosmia) has been self-reported by COVID-19 patients from different countries, consistent with the expression of the molecular factors mediating SARS-CoV-2 uptake into human olfactory epithelial supporting cells. However, a precise quantification of olfactory loss in asymptomatic COVID-19 carriers is missing to date.
METHODS: To quantitatively assess olfactory functions in asymptomatic COVID-19 patients, we designed and custom-built an olfactory-action meter that precisely measures detectability indices at different odor concentrations and an olfactory matching accuracy score with an array of monomolecular odors. Test results with normal healthy subjects served to optimize parameters such that the test can be executed in less than 20 minutes without compromising accuracy.
FINDINGS: Asymptomatic COVID-19 patients showed severe olfactory deficits with all parameters tested. Measuring the olfactory detection indices at low concentrations revealed olfactory deficits in 81% of patients. Patients with better detection scores showed significantly reduced olfactory matching accuracies compared to normal healthy subjects. Our quantification of olfactory loss, considering detection indices and matching performance, identifies 82% of the asymptomatic SARS-CoV-2 carriers, despite the fact that subjectively, only a few of the patients noticed a compromised ability to smell.
INTERPRETATION: Our findings from systematic analysis reveal that olfactory fitness can serve as a strong basis for identifying asymptomatic COVID-19 patients. Together, these results indicate olfactory sensory as well as cognitive deficits caused by SARS-CoV-2 infection. Detailed design specifications and protocols provided here should enable the development of a sensitive, fast and economical screening strategy that can be administered to large populations to prevent the rapid spread of COVID-19.
FUNDING STATEMENT: This work was supported by the Wellcome Trust – DBT India Alliance intermediate grant (IA/I/14/1/501306 to N.A.) and UGC NET Fellowship (A.B.).
DECLARATION OF INTERESTS: The authors declare that there is no conflict of interest.
ETHICS APPROVAL STATEMENT: All experimental procedures and protocols used in this study were approved by the ethics committees of IISER-Pune and BJGMC & SGH, Pune.
Keywords: Asymptomatic COVID-19 patients; Odor detection thresholds; anosmia; olfactory matching accuracy
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