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. 2021 Jan 12;10(1):62.
doi: 10.3390/pathogens10010062.

Psychophysical Evaluation of the Olfactory Function: European Multicenter Study on 774 COVID-19 Patients

Luigi Angelo Vaira  1   2   3 , Jerome R Lechien  1   4   5   6 , Mohamad Khalife  1   7 , Marzia Petrocelli  8 , Stephane Hans  1   5 , Lea Distinguin  1   5 , Giovanni Salzano  9 , Marco Cucurullo  10 , Piero Doneddu  2 , Francesco Antonio Salzano  11 , Federico Biglioli  10 , Fabrice Journe  4 , Andrea Fausto Piana  3   12 , Giacomo De Riu  1   2   3 , Sven Saussez  1   4   6
Affiliations

Psychophysical Evaluation of the Olfactory Function: European Multicenter Study on 774 COVID-19 Patients

Luigi Angelo Vaira et al. Pathogens. .

Abstract

Background: The objective evaluation of the olfactory function of coronavirus disease 2019 patients is difficult because of logistical and operator-safety problems. For this reason, in the literature, the data obtained from psychophysical tests are few and based on small case series.

Methods: A multicenter, cohort study conducted in seven European hospitals between March 22 and August 20, 2020. The Sniffin-Sticks test and the Connecticut Chemosensory Clinical Research Center orthonasal olfaction test were used to objectively evaluate the olfactory function.

Results: This study included 774 patients, of these 481 (62.1%) presented olfactory dysfunction (OD): 280 were hyposmic and 201 were anosmic. There was a significant difference between self-reported anosmia/hyposmia and psychophysical test results (p = 0.006). Patients with gastroesophageal disorders reported a significantly higher probability of presenting hyposmia (OR 1.86; p = 0.015) and anosmia (OR 2.425; p < 0.001). Fever, chest pain, and phlegm significantly increased the likelihood of having hyposmia but not anosmia or an olfactory disturbance. In contrast, patients with dyspnea, dysphonia, and severe-to-critical COVID-19 were significantly more likely to have no anosmia, while these symptoms had no effect on the risk of developing hyposmia or an OD.

Conclusions: Psychophysical assessment represents a significantly more accurate assessment tool for olfactory function than patient self-reported clinical outcomes. Olfactory disturbances appear to be largely independent from the epidemiological and clinical characteristics of the patients. The non-association with rhinitis symptoms and the high prevalence as a presenting symptom make olfactory disturbances an important symptom in the differential diagnosis between COVID-19 and common flu.

Keywords: COVID-19; SARS-CoV-2; anosmia; hyposmia; olfaction; olfactory dysfunction; parosmia; smell.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Olfactory and clinical outcome significant correlation.
Figure 2
Figure 2
Cross-tab analysis results. Abbreviations: OD: olfactory dysfunction, e.g., anosmia or hyposmia; OR: odds ratio; CI: confidence interval.
See this image and copyright information in PMC

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