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.