Quantitative assessment of olfactory dysfunction accurately detects asymptomatic COVID-19 carriers

Abstract

Background:COVID-19 threatens the global community because a large fraction of infected people areasymptomatic, yet can effectively transmit SARS-CoV-2. Finding and isolating these silent carriers is a crucialstep in confining the spread of the disease. A sudden loss of the sense of smell has been self-reported byCOVID-19 patients across different countries, consistent with expression of the molecular factors mediatingSARS-CoV-2 uptake into human olfactory epithelial supporting cells. However, precise quantification of olfac-tory loss in asymptomatic COVID-19 carriers is missing to date. Methods: To quantify olfactory functions in asymptomatic COVID-19 patients, we designed an olfactory-action meter that determines detectability indices at different odor concentrations and an olfactory matching accuracy score using monomolecular odors. The optimization of test parameters allowed us to reliably and accurately assess olfactory deficits in a patient within 20 minutes. Findings: Measurement of detection indices at low concentrations revealed a 50% reduction in asymptomaticCOVID-19 carriers. Further, patients with better detection scores showed significantly reduced olfactory matching accuracies compared to normal healthy subjects. Our quantification of olfactory loss, considering all parameters, identified 82% of the asymptomatic SARS-CoV-2 carriers with olfactory deficits. However, subjective evaluation, only 15% of the patients noticed a compromised ability to smell. Interpretation: Compromised olfactory fitness can serve as a strong basis for identifying asymptomaticCOVID-19 patients. Detailed design specifications and protocols provided here should enable the develop-ment of a sensitive, fast, and economical screening strategy that can be administered to large populations to prevent the rapid spread of COVID-19. Funding:This work was supported by the DBT Wellcome Trust India Alliance intermediate grant (IA/I/14/1/501,306 to N.A.) and UGC NET Fellowship (A.B.). All the funding sources played no roles in the study.© 2020 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license