TitleRecent smell loss is the best predictor of COVID-19 among individuals with recent respiratory symptoms
Publication TypeJournal Article
Year of Publication2021
AuthorsGerkin RC, Ohla K, Veldhuizen MG, Joseph PV, Kelly CE, Bakke AJ, Steele KE, Farruggia MC, Pellegrino R, Pepino MY, Bouysset C, Soler GM, Pereda-Loth V, Dibattista M, Cooper KW, Croijmans I, Di Pizio A, Ozdener MH, Fjaeldstad AW, Lin C, Sandell MA, Singh PB, Brindha VE, Olsson SB, Saraiva LR, Ahuja G, Alwashahi MK, Bhutani S, D'Errico A, Fornazieri MA, Golebiowski J, Hwang LD, Öztürk L, Roura E, Spinelli S, Whitcroft KL, Faraji F, Fischmeister FP, Heinbockel T, Hsieh JW, Huart C, Konstantinidis I, Menini A, Morini G, Olofsson JK, Philpott CM, Pierron D, Shields VDC, Voznessenskaya VV, Albayay J, Altundag A, Bensafi M, Bock MA, Calcinoni O, Fredborg W, Laudamiel C, Lim J, Lundström JN, Macchi A, Meyer P, Moein ST, Santamaría E, Sengupta D, Dominguez PR, Yanik H, Hummel T, Hayes JE, Reed DR, Niv MY, Munger SD, Parma V, Group GCCR
JournalChem Senses
Date Published12/2020

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.

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