Study population
This study was approved by institutional review boards of the CHU
Saint-Pierre, Brussels, Belgium, CHUSP210207 and of Epicura Hospital,
Baudour, Belgium, P2020011. From October 2020 to November 2020 patients
with a diagnosis of COVID-19 and olfactory dysfunction (OD) confirmed by
psychophysical tests were recruited after 2 weeks of onset of symptoms
at the Epicura Hospital, in Belgium. SARS-CoV-2 infection was diagnosed
by nasal swabbing and reverse transcriptase polymerase chain reaction
(RT-PCR). Symptoms were evaluated during the clinical course of the
disease with the COVID-19 Symptom Index7. Subjective
olfactory functions were evaluated with the smell and taste component of
the National Health and Nutrition Examination
Survey12. Fourteen to 15 days after onset of OD,
patients were invited to perform a sniffing test and to donate blood and
nasal secretion samples (nasal washing with physiological saline
solution was carried out and nasal secretions were sterile aspirated).
Subjects were categorized into anosmic, hyposmic and normosmic based on
their Sniff Test. Psychophysical olfactory assessments were performed
with the identification component of Sniffin’ Sticks tests (Medisense,
Groningen, Netherlands), which is a validated psychophysical olfactory
test using 16 smell pens. The final score ranges from 0 (none correctly
identified) to 16 (all correctly identified). Normative values
established normosmia as a score ranging between 12 and 16, hyposmia
between 9 and 11 and anosmia between 0 and 813. It
must be emphasized that at that time COVID-19 infections were associated
with significant mortality and vaccines were not available; it is for
this reason that only the identification part of the TDI was carried out
to reduce the risk of contamination of the research team.
Inclusion criteria consisted of adults with SARS-CoV-2 infection
identified through nasal swabs and positive RT-PCR and COVID-19 related
OD. Patients with a history of pre-COVID-19 pandemic OD, chronic or
self-reported acute rhinosinusitis (with regard to the European Position
Paper on Rhinosinusitis and Nasal Polyps guidelines) and dementia at the
time of evaluation were excluded. Socio-demographic and clinical data
were collected through a standardized online questionnaire or medical
records.