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. 2021 Jan;278(1):101-108.
doi: 10.1007/s00405-020-06267-2. Epub 2020 Aug 4.

Psychophysical evaluation of chemosensory functions 5 weeks after olfactory loss due to COVID-19: a prospective cohort study on 72 patients

Serge-Daniel Le Bon  1 , Nathalie Pisarski  2 , Justine Verbeke  2 , Léa Prunier  2 , Gaëtan Cavelier  2 , Marie-Paule Thill  2 , Alexandra Rodriguez  2 , Didier Dequanter  2 , Jérôme R Lechien  2 , Olivier Le Bon  3 , Thomas Hummel  4 , Mihaela Horoi  2
Affiliations

Psychophysical evaluation of chemosensory functions 5 weeks after olfactory loss due to COVID-19: a prospective cohort study on 72 patients

Serge-Daniel Le Bon et al. Eur Arch Otorhinolaryngol. 2021 Jan.

Abstract

Purpose: To evaluate the evolution of chemosensation via extended psychophysical testing in patients who suffered from sudden chemosensory loss due to coronavirus disease 2019 (COVID-19). Additionally, this study sought to determine whether odor threshold testing provided additional information on olfactory loss due to COVID-19 compared to the more common odor identification testing.

Methods: Prospective cohort study of patients with sudden chemosensory loss since February 2020 and confirmed COVID-19 infection via RT-PCR or serology testing. Olfactory function was tested extensively using the "Sniffin Sticks" test battery. In addition, we screened gustatory perception and nasal cooling sensations using psychophysical tests.

Results: Seventy-two patients completed the study. After a mean of 37 days, 37% of patients showed olfactory dysfunction, 7% were dysgeusic, and 48% showed signs of low sensitivity for cooling sensation. A longer duration of anosmia before smell improvement was correlated with lower olfactory function at 5 weeks. Odor threshold detection was more affected by COVID-19 compared to odor identification.

Conclusion: Five weeks after developing sudden chemosensory loss due to COVID-19, a high proportion of patients were dysosmic and showed signs of low nasal cooling sensitivity, whereas most of them had normal taste function. SARS-CoV-2 affected mainly odor thresholds, possibly suggesting that the major cause of loss of smell lies at the level of the olfactory neuroepithelium, rather than in the central nervous system.

Keywords: COVID-19; Chemosensory loss; Psychophysical test; SARS-CoV-2.

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Conflict of interest statement

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.

Figures

Fig. 1
Fig. 1
Flow diagram. Flow diagram illustrating cohort selection. COVID-19 coronavirus disease 2019, RT-PCR reverse transcriptase-polymerase chain reaction, IgG immunoglobulin G
Fig. 2
Fig. 2
Distribution of patients for each psychophysical test. Distribution of all 72 patients in different categories for each psychophysical test: olfactory (left), gustatory (middle), and trigeminal (right)
Fig. 3
Fig. 3
Olfactory subtest scores in each olfactory group. Median olfactory subtest scores across each olfactory group (error bars represent interquartile range). *p < 0.05. ***p < 0.005
See this image and copyright information in PMC

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