Randomization and blinding
loss of smell
DRUG INTERACTIONS, RECRUITMENT
Patients were assigned a number at time of recruitment, and this reference number was used for tracking during randomization and throughout the study protocol. Using a block randomization within each site, eligible participants were randomly assigned [Patients were informed that the purpose of the study was to investigate approaches for treating persistent loss of smell after COVID-19 and were provided information on the proposed regimen. Patients were informed that after baseline assessment, they would be randomized to a treatment involving taking an experimental supplement or placebo, with or without olfactory training. Patients were counseled that the supplement had no reported drug interactions or known safety-related concerns. Patients were also counseled regarding the placebo-controlled design of the study with blinding regarding supplement. They were informed that after baseline assessment, they would repeat the Sniffin’ Sticks assessment at 30, 60 and 90 days. Patients were counseled that their participation was voluntary and that they could withdraw from the study at any time.The study was performed in a double-blinded, placebo-controlled manner. The patients did not know their status with respect to placebo or um-PEA–LUT supplement (patient-blinding), although they were not blinded as to performing olfactory training. A single physician at each center performed the nasal endoscopy, and a second physician performed olfactory testing. The physician who performed olfactory testing remained blinded to experimental group throughout the study. The physician who performed the nasal endoscopy had knowledge of the experimental groups and did not participate in olfactory assessment. Having physician roles thus separated ensured that individuals performing assessments of olfactory recovery were always blinded to the patients’ treatment arm. Data obtained by the olfactory test were anonymized and results were collected on a protected Excel sheet shared by all the centers [Google (Mountain View, California, USA)].