Setting
Adult patients with confirmed COVID-19 and self-reported sudden-onset olfactory dysfunction were recruited through a public call from the Department of Anatomy of the University of Mons (Mons, Belgium). To be included, patients had to be not currently hospitalized (mild-to-moderate patients). The diagnosis of COVID-19 infection was based on the WHO interim guidance and symptoms of disease [8]. Individuals with self-reported sudden olfactory dysfunction and a clinical history suggestive of COVID-19 were invited to participate. A nasopharyngeal swab was performed to identify severe acute respiratory coronavirus-2 (SARS-CoV-2) via reverse transcription polymerase chain reaction (RT-PCR) for patient with symptom duration<14 days. In case of negative RT-PCR, serology for IgG and IgM to SARS-CoV-2 was realized. For patients with symptom duration ≥14 days, physicians performed serology (Figure 1). Only patients with a RT-PCR positive test or with positive IgG or IgM were included. Patients with a history of olfactory dysfunction before the pandemic, history of nasal surgery, chronic rhinosinusitis, head & neck trauma, or degenerative neurological disease were excluded from the study.