Effectiveness of olfactory training and topical corticosteroids for persistent post-COVID-19 anosmia and hyposmia: A prospective randomized controlled trial

Objective: To evaluate the effectiveness of olfactory training and topical intranasal corticosteroids in patients with persistent post-COVID-19 anosmia or hyposmia, and to compare recovery rates, duration of symptoms and changes in smell-identification scores across treatment groups.
Methodology: This prospective randomized controlled study was conducted at Colombo South Teaching Hospital, Sri Lanka, from 15 August 2021 to 5 January 2022. Patients were observed for four weeks after symptom onset to exclude spontaneous recovery. Those with persistent symptoms were allocated to four groups using computer-generated random numbers. Eighty-one participants were enrolled: 23 received olfactory training, 19 corticosteroids, 20 combined treatments, and 19 control. Olfactory function was assessed using the Quick Smell Identification Test (QSIT) and questionnaire.
Results: Most patients showed spontaneous improvement during the first month. Persistent cases demonstrated significant improvement in smell-identification scores in all intervention groups (p < 0.001), with greater improvement than controls. Olfactory training showed better early recovery than corticosteroids alone, with improvement in approximately 86% versus 64% at one month (p = 0.0086). Adding corticosteroids to olfactory training provided no additional significant benefit (p = 0.2249).
Conclusion: Olfactory training is an effective treatment for persistent post-COVID-19 anosmia and hyposmia. Combining topical corticosteroids with olfactory training offers no superior outcome. Larger trials with longer follow-up are required.