The COVANOS trial – insight into post-COVID olfactory dysfunction and the role of smell training

Matt Lechner, Jacklyn Liu, Nicholas Counsell, David C. Gillespie, Deepak Chandrasekharan, Ngan Hong Ta, Kiran Jumani, Sri V. Rao, John Rocke, Claire Williams, Abigail Tetteh, Rajesh Amnolsingh, Sadie Khwaja, Rachel Batterham, Carol H. Yan, Thomas A. Treibel, James C. Moon, Jane Woods, Ria Brunton, Jim BoardmanSantdeep Paun, Nicholas Eynon-Lewis, B. Nirmal Kumar, Samuel Jayaraj, Claire Hopkins, Carl Philpott, Valerie J. Lund

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)
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Background: Olfactory dysfunction is a cardinal symptom of COVID-19 infection, however, studies assessing long-term olfactory dysfunction are limited and no randomised-controlled trials (RCTs) of early olfactory training have been conducted.

Methodology: We conducted a prospective, multi-centre study consisting of baseline psychophysical measurements of smell and taste function. Eligible participants were further recruited into a 12-week RCT of olfactory training versus control (safety information). Patient-reported outcomes were measured using an electronic survey and BSIT at baseline and 12 weeks. An additional 1-year follow-up was open to all participants.

Results: 218 individuals with a sudden loss of sense of smell of at least 4-weeks were recruited. Psychophysical smell loss was observed in only 32.1%; 63 participants were recruited into the RCT. The absolute difference in BSIT improvement after 12 weeks was 0.45 higher in the intervention arm. 76 participants completed 1-year follow-up; 10/19 (52.6%) of participants with an abnormal baseline BSIT test scored below the normal threshold at 1-year, and 24/29 (82.8%) had persistent parosmia.

Conclusions: Early olfactory training may be helpful, although our findings are inconclusive. Notably, a number of individuals who completed the 1-year assessment had persistent smell loss and parosmia at 1-year. As such, both should be considered important entities of long-Covid and further studies to improve management are highly warranted.
Original languageEnglish
Pages (from-to)188-199
Number of pages12
Issue number3
Early online date28 Jul 2022
Publication statusPublished - 2022


  • COVID-19
  • anosmia
  • olfactory training
  • parosmia
  • quality of life

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