Recent Smell Loss Is the Best Predictor of COVID-19 Among Individuals With Recent Respiratory Symptoms
Richard C. Gerkin, Kathrin Ohla, Maria G. Veldhuizen, Paule V. Joseph, Christine E Kelly, Alyssa J. Bakke, Kimberley E. Steele, Michael C. Farruggia, Robert Pellegrino, Marta Yanina Pepino, Cédric Bouysset, Graciela M Soler, Veronica Pereda‐Loth, Michele Dibattista, Keiland W Cooper, Ilja Croijmans, Antonella Di Pizio, Mehmet Hakan Özdener, Alexander Wieck Fjældstad, Cailu Lin, Mari Sandell, Preet Bano Singh, V. Brindha, Shannon B. Olsson, Luís R. Saraiva, Gaurav Ahuja, Mohammed K Alwashahi, Surabhi Bhutani, Anna D’Errico, Marco Aurélio Fornazieri, Jérôme Golebiowski, Liang‐Dar Hwang, Lina Öztürk, E. Roura, Sara Spinelli, Katherine L. Whitcroft, Farhoud Faraji, Florian Ph. S. Fischmeister, Thomas Heinbockel, Julien Wen Hsieh, Caroline Huart, Iordanis Konstantinidis, Anna Menini, Gabriella Morini, Jonas Olofsson, Carl Philpott, Denis Pierron, Vonnie D. C. Shields, Vera V. Voznessenskaya, Javier Albayay, Aytuğ Altundağ, Moustafa Bensafi, María Adelaida Bock, Orietta Calcinoni, William Fredborg, Christophe Laudamiel, Juyun Lim, Johan N. Lundström, Alberto Macchi, Pablo Meyer, Shima T. Moein, Enrique Santamaría, Debarka Sengupta, Paloma Rohlfs Domínguez, Hüseyin Yanık, Thomas Hummel, John E. Hayes, Danielle R. Reed, Masha Y. Niv, Steven D. Munger, Valentina Parma, GCCR Group Author, Sanne Boesveldt, Jasper H. B. 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, María Dolors Guárdia, Kara C. Hoover, Noam Karni, Marta Navarro, Alissa A. Nolden, Patricia Portillo Mazal, Nicholas R. Rowan, Atiye Sarabi‐Jamab, Nicholas Archer, Ben Chen
Abstract
In a preregistered, cross-sectional study, we investigated whether olfactory loss is a reliable predictor of COVID-19 using 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 univariate and multivariate predictors of COVID-19 status and post-COVID-19 olfactory recovery. 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 univariate and multivariate models (ROC AUC = 0.72). Additional variables provide negligible model improvement. VAS ratings of smell loss were more predictive than binary chemosensory yes/no-questions or other cardinal symptoms (e.g., fever). Olfactory recovery within 40 days of respiratory symptom onset was reported for ~50% of participants and was best predicted by time since respiratory symptom onset. We find that quantified smell loss is the best predictor of COVID-19 amongst those with symptoms of respiratory illness. To aid clinicians and contact tracers in identifying individuals with a high likelihood of having COVID-19, we propose a novel 0-10 scale to screen for recent olfactory loss, the ODoR-19. We find that numeric ratings ≤2 indicate high odds of symptomatic COVID-19 (4 < OR < 10). Once independently validated, this tool could be deployed when viral lab tests are impractical or unavailable.