Objective/Hypothesis This study aims to determine the association between parosmia and clinically relevant recovery of olfactory function in patients with post‐infectious olfactory dysfunction (PIOD) receiving olfactory training. Study Design Retrospective cohort study. Methods This was a retrospective cohort study of patients with PIOD that received olfactory training. Adult patients with the major complaint of quantitative smell loss were recruited and treated at several ENT clinics in German between 2008 and 2018. The outcome was based on the association between smell‐loss related factors (including parosmia and phantosmia) and clinically relevant changes in overall and subdimension olfactory function of threshold, discrimination, and identification using binary logistic regression analysis. Results A total of 153 participants with PIOD were included. Clinically relevant improvements in overall olfactory function were more likely in those that had lower baseline olfactory function. Relevant improvements in discrimination function were more likely in those that had lower baseline olfactory function and those that had parosmia at the initial visit. Similarly, relevant improvements in odor identification were more likely in those that had a lower baseline olfactory function and in those who had parosmia at the first visit. Clinically significant improvements in odor threshold were more likely in those who were older in age. Conclusions This study demonstrated that the presence of parosmia is associated with clinically relevant recovery in olfactory discrimination and identification function in patients with PIOD receiving olfactory training. Level of Evidence 4 Laryngoscope, 131:618–623, 2021

Background: Olfactory training (OT) represents a therapeutic option for multiple etiologies of olfactory dysfunction (OD) that also benefits normosmic subjects. In this retrospective study, we report the effectiveness of OT and factors associated with relevant changes in olfactory function (OF) in large groups of normosmic participants and patients with OD, including a control group that performed no training. Methods: This was a retrospective pooled analysis including 2 treatment cohorts of 8 previously published studies. Adult participants that either presented with the major complaint of quantitative OD or normosmic volunteers were recruited at various ENT clinics and received OT or no training. The outcome was based on changes in objective olfactory test scores after OT. Results: A total of 601 patients with OD or normosmic subjects were included. OT was more effective compared to no training. No interaction was found between OT and OF. In multivariate analysis, higher baseline OF (adjusted odds ratio, aOR, 0.93) and posttraumatic (aOR, 0.29) or idiopathic OD (aOR, 0.18) compared to postinfectious causes were significantly associated with lower odds of relevant improvements in patients with OD receiving OT. Subgroup analysis of normosmic participants receiving OT further revealed a significant association of age and baseline olfactory function with improvements of overall OF. Conclusions: This study demonstrated that OT was more effective than no training in patients with various causes of OD. Additionally, baseline olfactory performance and etiology of OD were identified as important factors associated with relevant improvements after OT.

Objective: Olfactory training (OT) represents a therapeutic option for multiple etiologies of olfactory dysfunction (OD) that also benefits normosmic subjects. In this retrospective study, we report the effectiveness of OT and factors associated with relevant changes in olfactory function (OF) in large groups of normosmic participants and patients with OD, including a control group that performed no training. Methods: This was a retrospective pooled analysis including 2 treatment cohorts of 8 previously published studies. Adult participants that either presented with the major complaint of quantitative OD or normosmic volunteers were recruited at various ENT clinics and received OT or no training. The outcome was based on changes in objective olfactory test scores after OT. Results: A total of 601 patients with OD or normosmic subjects were included. OT was more effective compared to no training. No interaction was found between OT and OF. In multivariate analysis, higher baseline OF (adjusted odds ratio, aOR, 0.93) and posttraumatic (aOR, 0.29) or idiopathic OD (aOR, 0.18) compared to postinfectious causes were significantly associated with lower odds of relevant improvements in patients with OD receiving OT. Subgroup analysis of normosmic participants receiving OT further revealed a significant association of lower age and baseline olfactory function with improvements of overall OF. Conclusions: This study demonstrated that OT was more effective than no training in patients with various causes of OD. Additionally, baseline olfactory performance and etiology of OD were identified as important factors associated with relevant improvements after OT.

Objectives This study aims to determine the association between parosmia and clinically relevant recovery in olfactory function in patients with smell loss receiving olfactory training. Design and setting This was a retrospective cohort study of patients that received olfactory training. Adult patients with the major complaint of quantitative smell loss were recruited and treated at several ENT clinics in German between 2008 and 2018. Participants A total of 243 participants were included. Main outcome measures Changes in olfactory function after olfactory training. Age, gender, baseline olfactory function, etiology and duration of smell loss, duration of training, and presence of parosmia and phantosmia were assessed for their impact on clinically relevant changes in overall and subdimension olfactory function using binary logistic regression analysis. Results Relevant improvements in discrimination function were more likely in those that had lower baseline olfactory function, postinfectious reasons compared to posttraumatic or idiopathic causes and those that had parosmia at initial visit. Relevant improvements in odour identification were more likely in those that had a lower baseline olfactory function, female gender, and in those who had parosmia at the first visit. Clinically significant improvements in odour threshold were more likely in postinfectious causes compared to posttraumatic reasons and those who were older in age. Conclusions This study demonstrated that the presence of parosmia is associated with clinically relevant recovery in olfactory function in patients with smell loss receiving olfactory training. Key points 1. Parosmia is associated with clinically relevant improvements in discrimination and identification function in patients with smell loss receiving olfactory training. 2. Clinically relevant recovery of overall olfactory performance was more likely in those that had lower baseline olfactory function at initial visit and in postinfectious smell loss compared to posttraumatic or idiopathic causes. 3. Recovery of suprathreshold olfactory function discrimination and identification was distinct from threshold improvements.

Introduction The human sense of smell has different functions which can be categorized as “food,” “social,” and “environment.” Different questionnaires about the importance of olfaction in adults are available, but little attention has been paid to children and adolescents. Therefore, we aimed to develop a questionnaire about children’s personal significance of olfaction (ChiPSO). Methods The questionnaire was developed in two steps. The first questionnaire included 33 statements about the importance of olfactory information in daily life — covering three subscales “food,” “environment,” and “social” administered to 191 participants (mean age: 14.4 ± 1.7 years). The five best fitting items of each subscale were chosen for the final 15-item questionnaire. In the second part, we administered the developed questionnaire to 208 children and adolescents (mean age: 11.5 ± 3.5 years) who additionally underwent olfactory testing to investigate the association between olfactory function and questionnaire results. Participants were separated in two age groups: (i) 6–11 years (children), (ii) 12–17 years (adolescents). Results A significant influence of age on the total ChiPSO score and all three subscales with adolescents scoring higher than children was found. Additionally, there was a significant influence of sex in adolescents on total ChiPSO score and subscales “social” and “food” with girls scoring higher than boys. Conclusion We report an association between questionnaires results and olfactory performance. Additionally, olfactory information seems to be more important to adolescents compared to children and girls compared to boys. Implications The ChiPSO questionnaire is a practical tool to evaluate the importance of olfactory information in children and adolescents aged 6–17 years.