IRCT20210205050247N.

Study name	A comparative study of the effect of olfactory training and vitamin A in the olfactory loss of patients with covid‐19
Methods	Single‐centre, 3‐arm, double‐blind, parallel‐group RCT with 12 weeks duration of treatment and follow‐up
Participants	Adults with COVID‐19 and olfactory disturbance for more than 2 weeks  Inclusion criteria: Aged between 20 and 65 years Olfactory disturbance for more than 2 weeks No underlying disease, including hypertension, hypo/hyperthyroidism, seizures, diabetes, asthma, Bell's palsy (No details given on COVID‐19 status, but general inclusion criteria indicate that COVID‐19 positive patients will be included) Exclusion criteria: Patient not willing to participate Prolonged exposure to some chemical agents (detergents) History of head trauma History of sinus surgery or septorhinoplasty, rhinoplasty, turbinectomy and radiation therapy Neurodegenerative disease (e.g. Alzheimer's, Parkinson's, MS, epilepsy, seizures) Neuropsychiatric conditions (e.g. autism, Asperger's) Repeated use of the following drugs: metronidazole, benzocaine, clofibrate, amphotericin B, ampicillin, allopurinol, captopril, baclofen, codeine, carbamazepine and amphetamines Estimated sample size: 90 participants
Interventions	Intervention group A:  Olfactory rehabilitation for 12 weeks, using a kit that includes eucalyptus, lemon, rose and dianthus scents. Participants are asked to inhale each scent twice a day for 10 seconds each time. Intervention group B: Olfactory rehabilitation (as above) plus vitamin A tablets (10,000 units per day) for 12 weeks Control group:  The third group of patients will not receive any treatment intervention and these patients will be followed up for 12 weeks
Outcomes	Outcomes of interest in the review Primary outcomes: Presence of normal olfactory function Clinical recovery. Reported at 12 weeks using the Clinical Global Impression Severity (CGI‐S) scale. Unclear whether this will be reported as a dichotomous outcome. Serious adverse effects Not reported Change in sense of smell Primary outcome reported as smell identification, using the 4 scents in the olfactory rehabilitation kit Secondary outcomes include Olfactory Dysfunction Outcomes Rating (ODOR) questionnaire Unclear which of these assesses change in sense of smell Secondary outcomes: Prevalence of parosmia Not reported Change in sense of taste Not reported Disease‐related quality of life Olfactory Dysfunction Outcomes Rating (ODOR) at 12 weeks using pre and post test questionnaires. Unclear whether this questionnaire assesses disease‐related quality of life. Other adverse effects (including nosebleeds/bloody discharge) Not reported Other outcomes reported by the study: No additional outcomes
Starting date	18 February 2021
Contact information	Abolfazi Taheri Email: abolfzl.taheri@gmail.com
Notes	Study registered in Iran.  Anticipated study completion date 21 June 2021 It is unclear if participants will have had symptoms for < 4 weeks at baseline, therefore this trial may not be suitable for inclusion in this review. Further details will be obtained when the trial is published.