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Recent smell loss is the best predictor of COVID-19: a preregistered, cross-sectional study

By Richard C Gerkin, Kathrin Ohla, Maria G Veldhuizen, Paule Valery 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 Cooper, Iljia Croijmans, Antonella Di Pizio, M. Hakan Ozdener, Alexander W Fjaeldstad, Cailu 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, Jerome Golebiowski, Liang-Dar Hwang, Lina Ozturk, 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 Philpott, Denis Pierron, Vonnie D. C. Shields, Vera V. Voznessenskaya, Javier Albayay, Aytug Altundag, Moustafa Bensafi, María Adelaida Bock, Orietta Calcinoni, William Fredborg, Christophe Laudamiel, Juyun Lim, Johan N Lundstrom, Alberto Macchi, Pablo Meyer, Shima Moein, Enrique Santamaría, Debarka Sengupta, Paloma Rohlfs Dominguez, Huseyin Yanik, Sanne Boesveldt, Jasper de Groot, Caterina Dinnella, Jessica Freiherr, Tatiana Laktionova, Sajidxa Mariño, Erminio Monteleone, Alexia Nunez-Parra, Olagunju Abdulrahman, Marina Ritchie, Thierry Thomas-Danguin, Julie Walsh-Messinger, Rashid Al Abri, Rafieh Alizadeh, Emmanuelle Bignon, Elena Cantone, Maria Paola Cecchini, Jingguo Chen, Maria Dolors Guàrdia, Kara C. C. Hoover, Noam Karni, Marta Navarro, Alissa Nolden, Patricia Portillo Mazal, Nicholas R. Rowan, Atiye Sarabi-Jamab, Nicholas S. Archer, Ben Chen, Elizabeth A. Di Valerio, Emma L. Feeney, Johannes Frasnelli, Mackenzie R Hannum, Claire Hopkins, Hadar Klein, Coralie Mignot, Carla Mucignat-Caretta, Yuping Ning, Elif E. Ozturk, Mei Peng, Ozlem Saatci, Elizabeth A. Sell, Carol H. Yan, Raul Alfaro, Cinzia Cecchetto, Gérard Coureaud, Riley Herriman, Jeb M. Justice, Pavan Kumar Kaushik, Sachiko Koyama, Jonathan B Overdevest, Nicola Pirastu, Vicente Ramirez, S. Craig Roberts, Barry Smith, Hongyuan Cao, Hong Wang, Patrick Balungwe, Marius Baguma, Thomas Hummel, John E Hayes, Danielle R Reed, Masha Y Niv, Steven D. Munger, Valentina Parma

Posted 26 Jul 2020
medRxiv DOI: 10.1101/2020.07.22.20157263

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 [&le;]2 indicate high odds of symptomatic COVID-19 (10<OR<4), especially when viral lab tests are impractical or unavailable.

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