4.2 Prevalence of COVID-19 in New Onset Olfactory Dysfunction
Cohorts
Due to the differences in public health approaches and the availability
of testing it is difficult to demonstrate clear associations between new
onset OD and COVID-19 positivity. There were however three studies that
did have PCR results for patients presenting with OD since the start of
the COVID-19 pandemic. In table 2 we demonstrate that there is a high
prevalence of COVID-19 positivity in patients currently presenting with
OD.
The American Academy of Otolaryngology – Head and Neck Surgery
(AAO-HNS) developed a COVID-19 Anosmia reporting tool for clinicians.
Responses were collected from clinicians around the world relating to
the association of COVID-19 and anosmia. They do not clearly state if
all submitted patients had PCR testing performed. 237 entries were
analysed; anosmia was the initial symptom in more than 25% of cases,
27% had noticed some improvement and in 40% was the symptom that led
to a test being performed .
Bagheri et al conducted a widely completed online survey (in an
unpublished paper made available before peer review), of the general
population in Iran, to identify patients with OD since the inception of
the outbreak in their country. They demonstrated high numbers of people
who had experienced OD in their cohort. Their respondents were commonly
female (71%) and experienced sudden onset in their OD (76%). Only
1.1% were admitted to hospital for treatment indicating a largely mild
disease when OD was experienced. In a similar online questionnaire
study, conducted in the UK, by Hopkins et al the demographic features
were replicated. The majority of this British population with OD
reported complete loss of smell (74.4%) and in 16% of cases it was
their only symptom. A proportion of these patients did report receiving
a PCR test with a 74% positive rate in this sub-group .
Gane et al present a case series of 11 patients presenting with sudden
onset anosmia during the epidemic in the United Kingdom. In 5 of these
patients it was an isolated symptom and just one of these patients were
self-isolating . Gengler et al present findings (in an unpublished paper
made available before peer review) from a French case series, not
currently published, which demonstrated a positive COVID-19 nasal PCR
swab in 94% of their 55-patient series .
Table 3 demonstrates the average ages and gender proportions of the six
studies with OD cohorts.