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Review
. 2022 Apr;42(Suppl. 1):S20-S35.
doi: 10.14639/0392-100X-suppl.1-42-2022-03.

Results from psychophysical tests of smell and taste during the course of SARS-CoV-2 infection: a review

Eleonora M C Trecca  1   2 , Michele Cassano  1 , Francesco Longo  2 , Paolo Petrone  3 , Cesare Miani  4 , Thomas Hummel  5 , Matteo Gelardi  1
Affiliations
Review

Results from psychophysical tests of smell and taste during the course of SARS-CoV-2 infection: a review

Eleonora M C Trecca et al. Acta Otorhinolaryngol Ital. 2022 Apr.

Abstract

Risultati dei test psicofisici olfattivi e gustativi durante l’infezione COVID-19: revisione della letteratura.

Riassunto: La maggioranza degli studi ha valutato la capacità olfattiva e gustativa nei pazienti COVID-19 con questionari e autovalutazione. Data l’eterogeneità della letteratura pubblicata, lo scopo di questa ‘review’ è stato quello di analizzare gli articoli sull’argomento, focalizzando l’attenzione sui test psicofisici. È stata eseguita una ricerca su PubMed e Web of Science da dicembre 2019 a novembre 2021. I principali criteri di inclusione sono stati articoli in lingua inglese, che studiavano le caratteristiche cliniche dell’olfatto e del gusto nei pazienti COVID-19 utilizzando test soggettivi, psicofisici e ‘imaging’ radiologico. In totale sono stati identificati 638 articoli e di questi ne sono stati inclusi 66. In 31 studi è stata eseguita una valutazione soggettiva, mentre in 30 sono stati utilizzati test psicofisici e in 5 tecniche di ‘imaging’ radiologico. La prevalenza della disfunzione chemosensoriale è stata l’argomento più studiato, seguita dal tempo di recupero. Per quanto riguarda la valutazione psicofisica, gli Sniffin’ Sticks sono stati utilizzati in 11 articoli e il test del Connecticut Chemosensory Clinical Research Center in altri 11. La performance della soglia olfattiva è stata la più intaccata rispetto alle capacità di discriminazione e identificazione in linea con l’ipotesi di un tropismo del virus COVID-19 per la mucosa olfattoria. La tempistica ha influenzato significativamente i risultati del test psicofisico con solo il 20% dei pazienti affetti da disfunzione olfattiva dopo un mese dall’infezione.

Keywords: COVID-19; anosmia; infections; olfaction disorders; rhinology; smell; taste.

Plain language summary

Only a few studies have assessed smell and taste in Coronavirus Disease 2019 (COVID-19) patients with psychophysical tests, while the majority performed self-rating evaluations. Given the heterogeneity of the published literature, the aim of this review was to systematically analyse the articles on this topic with a focus on psychophysical testing. A search on PubMed and Web of Science from December 2019, to November 2021, with cross-references, was executed. The main eligibility criteria were English-language articles, investigating the clinical features of olfaction and gustation in COVID-19 patients using self-rating assessment, psychophysical testing and imaging techniques. A total of 638 articles were identified and 66 were included. Self-rating assessment was performed in 31 studies, while psychophysical testing in 30 and imaging techniques in 5. The prevalence of chemosensory dysfunction was the most investigated topic, followed by the recovery time. About the psychophysical assessment, the extended version of the Sniffin’ Sticks was used in 11 articles and the Connecticut Chemosensory Clinical Research Center test in another 11. The olfactory threshold performance was the most impacted compared to the discrimination and identification capacities in accordance with the hypothesis of a tropism of SARS-CoV-2 for the olfactory mucosa. The timing significantly influenced the results of the psychophysical testing with 20% of patients presenting olfactory dysfunction at one month after infection.

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Figures

Figure 1.
Figure 1.
PRISMA (Primary Reporting Items for Systematic Reviews and Meta-analyses) flow diagram.
Figure 2.
Figure 2.
Topics of included articles about COVID-19 chemosensory dysfunction from December 2019 to November 2021. Prevalence of chemosensory dysfunction was the most investigated topic.
Figure 3.
Figure 3.
Recovery time of olfactory dysfunction evaluated using psychophysical testing. The figure shows the prevalence of patients suffering from olfactory dysfunction according to the timing of SARS-CoV-2 infection.
See this image and copyright information in PMC

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