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

Abstract

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.

• Authors: M Lechner, J Liu, N Counsell, D Gillespie, D Chandrasekharan, N H Ta, K Jumani, R Gupta, S Rao-Merugumala, J Rocke, C Williams, A Tetteh, R Amnolsingh, S Khwaja, R L Batterham, C H Yan, T A Treibel, J C Moon, J Woods, R Brunton, J Boardman, S Paun, N Eynon-Lewis, B N Kumar, S Jayaraj, C Hopkins, C Philpott, V J Lund
• Journal: Rhinology (Rhinology) Vol. 60 Issue 3 Pg. 188-199 (Jun 01 2022) ISSN: 0300-0729 [Print] Netherlands
• PMID: 35901492 (Publication Type: Multicenter Study, Journal Article)

Topics

• Humans
• Smell
• COVID-19 (complications)
• Anosmia (etiology)
• Olfactory Training
• Olfaction Disorders (etiology, diagnosis)