The best COVID-19 predictor is recent smell loss: a cross-sectional study

Global Consortium for Chemosensory Research (GCCR), Richard C. Gerkin, Kathrin Ohla, Maria Geraldine Veldhuizen, Paule V. Joseph, Christine E. Kelly, Alyssa J. Bakke, Kimberley E. Steele, Michael C. Farruggia, Robert Pellegrino, Marta Y. Pepino, Cédric Bouysset, Graciela M. Soler, Veronica Pereda-Loth, Michele Dibattista, Keiland W. Cooper, Ilja Croijmans, Antonella Di Pizio, M. Hakan Ozdener, Alexander W. FjaeldstadCailu Lin, Mari A. Sandell, Preet B. Singh, V. Evelyn Brindha, Shannon B. Olsson, Luis R. Saraiva, Gaurav Ahuja, Mohammed K. Alwashahi, Surabhi Bhutani, Anna D'Errico, Marco A. Fornazieri, Jérôme Golebiowski, Liang-Dar Hwang, Lina Öztürk, Eugeni Roura, Sara Spinelli, Katherine L. Whitcroft, Farhoud Faraji, Florian Ph.S Fischmeister, Thomas Heinbockel, Julien W. Hsieh, Caroline Huart, Iordanis Konstantinidis, Anna Menini, Gabriella Morini, Jonas K. Olofsson, Carl M. Philpott, Denis Pierron, Vonnie D. C. Shields, Vera V. Voznessenskaya, Javier Albayay

Research output: Working paper


Background: COVID-19 has heterogeneous manifestations, though one of the most common symptoms is a sudden loss of smell (anosmia or hyposmia). We investigated whether olfactory loss is a reliable predictor of COVID-19. Methods: This preregistered, cross-sectional study used a crowdsourced questionnaire in 23 languages to assess symptoms in individuals self-reporting recent respiratory illness. We quantified changes in chemosensory abilities during the course of the respiratory illness using 0-100 visual analog scales (VAS) for participants reporting a positive (C19+; n=4148) or negative (C19-; n=546) COVID-19 laboratory test outcome. Logistic regression models identified singular and cumulative predictors of COVID-19 status and post-COVID-19 olfactory recovery. Results: Both C19+ and C19- groups exhibited smell loss, but it was significantly larger in C19+ participants (mean±SD, C19+: -82.5±27.2 points; C19-: -59.8±37.7). Smell loss during illness was the best predictor of COVID-19 in both single and cumulative feature models (ROC AUC=0.72), with additional features providing no significant model improvement. VAS ratings of smell loss were more predictive than binary chemosensory yes/no-questions or other cardinal symptoms, such as fever or cough. Olfactory recovery within 40 days was reported for ~50% of participants and was best predicted by time since illness onset. Conclusions: As smell loss is the best predictor of COVID-19, we developed the ODoR-19 tool, a 0-10 scale to screen for recent olfactory loss. Numeric ratings ≤2 indicate high odds of symptomatic COVID-19 (10<OR<4), especially when viral lab tests are impractical or unavailable.Competing Interest StatementRichard C Gerkin: Advisor for Climax Foods, Equity Compensation (RCG) John E. Hayes: Dr. Hayes has received speaker honoraria, consulting fees, and/or travel expenses from numerous organizations, including federal agencies, universities, nonprofit organizations, trade groups, and for-profit corporations, to present data on taste biology, perception and consumer behavior. Additionally, the Sensory Evaluation Center at Penn State routinely conducts product tests for industrial clients to facilitate experiential learning for students. (JEH) Thomas Hummel: Since 2018 Thomas Hummel did research together with and received funding from Sony, Stuttgart, Germany; Smell and Taste Lab, Geneva, Switzerland; Takasago, Paris, France: aspuraclip, Berlin, Germany. (TH) Christine E Kelly: AbScent is a charity registered in England and Wales #1183468 (CEK) Christophe Laudamiel: Author has received funding from scent related institutions and corporations, however for work totally unrelated to the field of the present study. (CL) Carl M. Philpott: Trustee of Fifth Sense (UK charity for patients with smell and taste disorders) (CMP) Funding StatementNo external funding was receivedAuthor DeclarationsI confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.YesThe details of the IRB/oversight body that provided approval or exemption for the research described are given below:This preregistered,15 cross-sectional online study was approved by the Office of Research Protections of The Pennsylvania State University (STUDY00014904), is in accordance with the revised Declaration of Helsinki, and is compliant with privacy laws in the U.S.A. and the European Union. All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived.YesI understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable.YesThe data and annotated code will be available on GitHub ( upon publication.
Original languageEnglish (US)
PublisherCold Spring Harbor Laboratory Press
Number of pages35
StatePublished - Jan 1 2020

Publication series



  • Coronavirus
  • COVID-19
  • severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)
  • Novel coronavirus
  • 2019-nCoV
  • Pandemic

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    Global Consortium for Chemosensory Research (GCCR), Gerkin, R. C., Ohla, K., Veldhuizen, M. G., Joseph, P. V., Kelly, C. E., Bakke, A. J., Steele, K. E., Farruggia, M. C., Pellegrino, R., Pepino, M. Y., Bouysset, C., Soler, G. M., Pereda-Loth, V., Dibattista, M., Cooper, K. W., Croijmans, I., Di Pizio, A., Ozdener, M. H., ... Albayay, J. (2020). The best COVID-19 predictor is recent smell loss: a cross-sectional study. (medRxiv). Cold Spring Harbor Laboratory Press.