PAPER OF THE MONTH: Olfactory and gustatory dysfunctions as a clinical presentation of mild‑to‑moderate forms of the coronavirus disease (COVID‑19): a multicenter European study

For May 2020, we have selected: Lechien JR, Chiesa-Estomba CM, De Siati DR et al. Olfactory and gustatory dysfunctions as a clinical presentation of mild‑to‑moderate forms of the coronavirus disease (COVID‑19): a multicenter European study.

Eur Arch Otorhinolaryngol. 2020 Apr 6. doi: 10.1007/s00405-020-05965-1. [Epub ahead of print]

The spread of the COVID-19 infection in Europe has highlighted a new atypical presentation of the disease: patients with olfactory and gustatory dysfunctions.

Our paper of the month reports a prospective multicentre study with the aim of investigating the occurrence of olfactory and gustatory dysfunctions in patients with laboratory-confirmed COVID-19 infection.

Patients with laboratory-confirmed COVID-19 infection were recruited from 12 European hospitals. The following epidemiolocal data were collected: age, sex, ethnicity, comorbidities, and general and otolaryngological symptoms.

The COVID-19 Task Force of the Young Physicians Group of the International Federation of Otorhinolarygological Societies (YO-IFOS), including otolaryngologists from North America, Europe, and Asia, selected relevant features composing the questionnaires.

Furthermore, patients completed olfactory and gustatory questionnaires based on the smell and taste component of the National Health and Nutrition Examination Survey, and the short version of the Questionnaire of Olfactory Disorders- Negative Statements (sQOD-NS).

Four hundred and seventeen Covid-19 confirmed patients with olfactory and gustatory dysfunctions were recruited.

Inclusion criteria were: adult (> 18 years old); laboratory-confirmed COVID-19 infection (by reverse transcription polymerase chain reaction, RT-PCR); native language speaking patients; and patients had to be clinically able to fill the questionnaire.

The exclusion criteria were: patients with olfactory or gustatory dysfunctions before the pandemic; patients without a laboratory-confirmed COVID-19 infection diagnosis; patients who were in the intensive care unit at the time of the study.

The results of this study confirmed the involvement of the olfactory and gustatory networks in this infection. 85.6% of participants had olfactory dysfunction and 79.6% of this patient group was anosmic. Olfactory dysfunction appeared before (11.8%), after (65.4%) or at the same time as the appearance of general or ENT symptoms (22.8%). Notably, olfactory dysfunction persisted after the resolution of other symptoms in 63.0% of cases. 72.6% of these patients recovered olfactory function within the first 8 days following resolution of the disease.

Gustatory disorders (including the impairment of salty, sweet, bitter, and sour taste modalities) were reported by 88.8% patients. Gustatory dysfunction consisted of reduced/discontinued or distorted ability to taste flavours in 78.9% and 21.1% of patients, respectively.

Of note, the two abnormalities were not present together in all patients. In this regard, 53.9% patients had isolated olfactory dysfunction, 22.5% had isolated gustatory dysfunction and 23.6% had both olfactory and gustatory dysfunctions. However, there was a significant positive association between olfactory and gustatory dysfunctions (p < 0.001).

The authors investigated whether the modality of the symptoms changed over time and it was discovered that olfactory and gustatory disorders were constant in 72.8% of patients, whereas they fluctuated in 23.4% of patients. Females were significantly more affected by smell and taste symptoms compared to male patients.

This study confirmed a high prevalence of olfactory and gustatory symptoms in patients with Covid-19 and the authors recommended performing Covid-19 testing in patients with olfactory and gustatory abnormalities, even in absence of other symptoms, to avoid potential spread of the infection.

The pathophysiological mechanisms leading to olfactory and gustatory dysfunctions in the COVID-19 infection are still unknown. Moreover, it is still unknown if there is a group of patients developing long-term dysfunction of smell and taste senses. The hypothesis that human coronavirus might invade the olfactory bulb to gain entry to the central nervous system is the subject of future research.

“The Covid-19 pandemic is the greatest global healthcare challenge for many decades’, commented Prof Johann Sellner of Landesklinikum Mistelbach-Gänserndorf, Austria. “The spectrum of neurological complications needs to be better characterized; further insights will be provided by the EANCore initiative.”