Isolated, sudden, recoverable olfactory dysfunction: a pathognomonic
sign of COVID-19
Objectives This study aimed to define the clinical features of anosmia,
a symptom observed in patients with coronavirus disease 2019 (COVID-19).
Methods The presence of olfactory symptoms, such as loss of smell, in
COVID-19 patients and their relationship with the disease process were
evaluated. Results A total of 217 patients with COVID-19 were evaluated,
of which 135 patients were interviewed via phone calls. The patients
were divided into four subgroups: group 1 had only olfactory complaints
(isolated, sudden-onset loss of smell); group 2 had isolated,
sudden-onset loss of smell, followed by typical COVID-19 complaints;
group 3 initially had typical COVID-19 complaints, but gradually
developed olfactory complaints; and group 4 had no olfactory complaints.
In total, 59.3% of the patients had olfactory complaints. In groups
1–3, the odor scores after the disease were significantly lower than
those before the disease; this decrease was more evident in groups 1 and
2 than in group 3 (p = 0.003, p = 0.000, and p = 0.014, respectively).
Groups 1 and 2 had a greater loss of smell than group 3 (7.8 ± 2.1 in
groups 1 and 2 vs. 6.2 ± 2.6 in group 3; p = 0.01). The odor scores
completely returned to the pre-disease values in 51.2% of patients with
olfactory dysfunction (41 patients); the mean duration of loss of smell
was 7.1 ± 2.4 days. Conclusion Timely detection of anosmia is important
in patients with COVID-19 in order to help control the spread of this
highly contagious disease.