4. Discussion:
4.1 Key outcomes and comparisons with recent literature:
We chose to look at OTDs combined due to their close relationship and smell dysfunction being the predominant cause of most taste complaints.6 OTDs were common in our cohort at 55.8% and were associated with fever, but not cough or shortness of breath. As study participants were identified from a database of SARS-COV2 positive results, and criteria for a test to be performed was restricted to those with at least one of the three core symptoms, we are unable to comment on isolated anosmia.
OTD prevalence was not as high as the 85% reported in a European multicentre study.3 However, the mean age of participants in that study was lower at 36 years, and criteria for testing may have been less restrictive but was not reported. Hopkins et al conducted a survey on 2428 patients with new onset anosmia during the pandemic. Although 51% had other symptoms related to COVID-19, only 80 participants had been tested for COVID-19 and therefore we are unable to quantify what proportion are attributable to the virus.7
It has been suggested that, unlike other related viruses, the anosmia is not associated with nasal blockage.1,3 Interestingly, in our cohort loss of smell was significantly associated with nasal blockage but not with other sinus symptoms, such as nasal discharge, facial pain or ear fullness. COVID-19 related anosmia has been associated with being female and although 59% of those with OTDs in our population were female, this was not statistically significant.2
Sense of smell declines with advancing age and therefore it is perhaps unsurprising that a change in smell and taste is associated with younger age in our sample6. An Italian cross-sectional study of 59 inpatients reported a prevalence of OTD at 33%, similar to our inpatient rate at 37%, and significantly lower than those reported by staff and outpatients.8 Moein et al identified 59 of 60 COVID-19 inpatients with objective smell dysfunction using UPSIT and found no correlation with sex, disease severity or comorbidities.9 Therefore, it is possible that differences in the self-reporting of OTDs may exist as opposed to differences in objective rates between inpatients and outpatients. Reasons for this could include staff and outpatients average younger age and likely better baseline sense of smell and that inpatients are more unwell and perhaps less likely to notice the more minor symptoms such as OTD and a sore throat.
Anosmia has been identified as a potential early indicator of disease, however, OTDs in this sample were more commonly reported as starting after or at the same time as core symptoms, similar to Lechien et al’s European cohort.2,3 High early recovery rates of anosmia of over 50% support that of recent studies.7,10