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.