Assessment of two olfactory training methods for post-COVID-19 loss of olfaction: Classical and intensive.

Objectives: To determine whether intensive olfactory training provides better chances of recovery than classic protocols in persistent dysosmia after Covid-19.

Introduction: In the literature, olfactory training holds pride of place in the management of post-infection olfactory disorder, with a classic 4-odor protocol. On the other hand, few studies have assessed the benefit of more intensive training.

Materials and methods: This prospective randomized clinical trial (No. 2020-A01397-32) assessed olfactory training for persistent dysosmia due to COVID-19, with 5 weeks' to 12 months' progression. Patients were divided between 2 groups, receiving a classical 4-odor protocol (n=49) or an intensive 8-odor protocol (n=30). Olfaction was assessed in consultation on the Sniffin' Sticks test, the DyNaChron self-reported olfaction questionnaire and a visual analogue scale (VAS), at inclusion (V1) and at 4 and 8 months (V2 and V3, respectively).

Results: Both protocols significantly improved subjective olfactory assessment on VAS, with non-significant trends for improvement on psychophysical tests. There was no significant difference in olfactory recovery between the classic and intensive protocols. Adhesion to the training program decreased markedly beyond 4 months.

Conclusion: Intensive olfactory training did not increase the chances of olfactory recovery compared to the classic protocol in a population with persistent dysosmia following COVID-19 infection.