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Bagheri et al conducted a widely completed online survey (in an unpublished paper made available before peer review), of the general population in Iran, to identify patients with OD since the inception of the outbreak in their country.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 Gengler et al present findings (in an unpublished paper made available before peer review) from a French case series, not currently published, which demonstrated a positive COVID-19 nasal PCR swab in 94% of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.