Introduction
At the time of writing (May 12th 2020), there have been 226,000
confirmed cases of COVID-19 in the UK. Using data available through the
COVID Symptom tracker which is monitoring over 2.5 million members of
the public, it is estimated that there have been in excess of 2 million
cases.
The British Rhinological Society (BRS) and ENTUK were the first to
report that loss of smell or taste may be an important symptom. There
has been a rapid growth in the evidence base supporting the initial
observations made by the BRS/ENTUK that an apparent rise in incidence of
anosmia reflected the onset of the COVID-19 pandemic(1-3).
We have undertaken a systematic review, which suggests a prevalence of
self-reported loss of sense of smell in 50% of patients. Emerging data
suggests a high rate of early recovery, but at 4-6 weeks after onset
approximately 10% patients have not experienced any recovery and still
self-report severe loss of sense of smell. Applying the prevalence and
recovery rates to estimated cases in the UK, there are likely already
more than 100,000 new cases of severe loss of sense of smell persisting
beyond the first few weeks of COVID infection. We do not yet know the
potential for long term recovery, but we anticipate that both GPs and
ENT doctors will see an increase in the number of patients presenting
for advice.
As there is a high rate of spontaneous recovery reported across all
studies within 2 weeks of onset of symptoms therefore we will consider
only patients where duration of loss or reduction of sense smell (LOS),
with or without loss of sense of taste, is longer than 14 days or more.
Furthermore, respiratory deterioration typically occurs between day 7 –
12 after onset of symptoms and this period should be allowed to pass
before considering specific treatments, particularly as the safety of
treatments in the setting of severe COVID-19 has yet to be fully
established for any treatments considered.
Many patients report loss of flavour (due to loss of retronasal
olfactory function) as loss of taste. Some reports suggest that true
taste disturbance is also present in COVID-19. However, we will not
attempt to differentiate or address this in this guidance, which will
focus on self-reported loss of sense of smell
The aim of this guidance is to provide evidence-based recommendations
for the management of patients with COVID-19 related anosmia, while at
the same time trying to optimise use of resources but ensuring those
with alternative pathologies are identified in a timely manner. We
therefore considered investigation of patients presenting with loss of
sense of smell during the COVID pandemic and management of post-COVID
loss of sense of smell.