Strengths and weaknesses of the study
The present study uses a comprehensive dataset including relevant olfactory demographics and smell-loss related variables to assess different factors associated with clinically relevant improvements after OT. However, this study also has limitations. Firstly, although we were able to depict the exact training type in all studies, subtle differences in odours used might have biased our results. Since previous studies have shown that the training effect was consistent among different training protocols, these differences might not have affected the outcome after OT to a large extent.11,12 Secondly, the missing values may have biased our results and compromised the statistical power. Nevertheless, our results are an important reference point on OD-related variables for clinicians during counselling of patients with smell loss.