Discussion
Postviral olfactory loss (PVOL) is one of the most common causes of olfactory dysfunction. Pathogens include those viruses causing the common cold comprising influenza-, parainfluenza-, rhino- and coronavirus(4). Olfactory dysfunction can have a significant negative impact on quality of life(5). COVID-19 has been shown to be associated with a high prevalence of loss of sense of smell and taste, and early reports on recovery suggest that while this may be transient in many cases, resolving in 7-14 days, at least 10% will have severe deficits lasting beyond the first 4 – 6 weeks(6). Longer term data is not yet available. Historical reports of spontaneous recovery following post-viral loss likely exclude patients with transient loss due to under-reporting, but instead capture those with loss persisting at least in beyond the first few weeks. Nevertheless, two retrospective studies, including 791 and 262 patients respectively, indicate that between one third to two thirds of patients with PVOL will experience a clinically relevant improvement(5, 7, 8). However, recovery can sometimes take several years. Given the high incidence of COVID-19 it is anticipated that both primary care and ENT specialists will see a surge in patients seeking advice.
The applied RAND/UCLA methodology allowed for timely development of appropriateness criteria for the medical management, referral guidelines, endoscopy and strategies for imaging of patients with new onset anosmia. Indeed, time was the essence in this study as many doctors including general practitioners and ENT surgeons are expected to meet a significant number of patients with post-COVID loss of sense of smell in the near future (8). The flow chart created should assist with overview and appropriate management. This methodology combined the best available evidence with the cooperative judgment of experts in the field. There exists solid evidence for the use of olfactory training in the treatment of PVOL (5–7). Smell training is also recommended by the expert panel in this study for the management of new onset anosmia during the COVID-19 pandemic. Many different medications have been proposed to treat PVOL, including oral corticosteroids, topical corticosteroids, zinc sulfate, alpha lipoic acid, theophylline, caroverine, vitamin A, Ginkgo biloba, sodium citrate and minocycline. However, the evidence to support use of these medical treatments for PVOL is limited and no large randomized controlled trials (RCT) exist. The expert panel only recommended use of INCS in patients with anosmia and concomitant nasal symptoms and made recommendations against the use of alpha lipoic acid.
We were unable to reach consensus at the 70% threshold determined a priori but did achieve consensus at a 60% threshold for 3 treatments; topical steroid rinses, omega-3 supplements and oral corticosteroids (but only if no symptoms of COVID or after full resolution of symptoms). We did agree that these could be considered as optional medical treatments, but after discussion with patients regarding the uncertainty surrounding usage and assessment of risks at an individual level.
Delivery of ENT care will be challenging as we undertake a graduated return to elective practice. In particular, use of nasal endoscopy needs to be carefully considered due to its potential to be an aerosol generating procedure. Waiting times for ENT care will likely significantly increase. For many patients with confirmed COVID-19 infection and anosmia, specialist review and further investigation will not be required; however, serology testing will be required for those who had been unable to access testing at the time of active infection. We have identified those who will benefit from specialist review, and also provided supporting material to assist primary care doctors, who may have had quite limited experience in this area. We plan to develop further educational material for both GP’s and ENT surgeons. Patient groups including AbScent and Fifth Sense will play an important role in patient support, we are delighted to be partnering with both groups to provide patient information leaflets (Appendix 3) and further support through a variety of different media.
A strength of the method was to give each panellist an equal voice in the Delphi process, and maintaining anonymity throughout the scoring process. The methodology is also ideally suited to the social distancing requirements of the current pandemic in place of nominal group techniques where face-to-face discussion is required. A limitation is that the guidelines are based on the panellist’s interpretation of the best available evidence and may be influenced by their own training and clinical experience. Another limitation may be the group composition as it is generally recommended that the group is multidisciplinary(9); it would have benefited from the inclusion of both primary care doctors and patient representatives.
We look forward to a time when the COVID pandemic will pass – and these guidelines no longer be needed. They have been developed for a time when the prevalence of COVID-19 related loss of smell is high, but they will need to be reconsidered when the relative likelihood of differential diagnoses increase – particularly with regard to indications for further imaging. Although considered with regard to COVID-19 related anosmia, the recommendations on treatments may be applied to all post-viral anosmia, although the risk – benefit analysis may need to be modified. Finally, it should be noted that as our experience of COVID-19 grows, our guideline will likely need to evolve. We hope that the newfound spotlight on loss of sense of smell and taste will drive clinical research and lead to the development of novel treatment options for patients with post-viral loss, and that greater understanding exists for those who do not recover.