Developing a core outcome set for clinical trials in olfactory disorders: a COMET initiative

Statement of problem: Evaluating the effectiveness of the management of Olfactory Dysfunction (OD) has been limited by a paucity of high-quality randomised and/or controlled trials. A major barrier is heterogeneity of outcomes in such studies. Core outcome sets (COS) -standardized sets of outcomes that should be measured/reported as determined by consensus-would help overcome this problem and facilitate future meta-analyses and/or systematic reviews (SRs). We set out to develop a COS for interventions for patients with OD.Methods: A long-list of potential outcomes was identified by a steering group utilising a literature review, thematic analysis of a wide range of stakeholders'views and systematic analysis of currently available Patient Reported Outcome Measures (PROMs). A subsequent e-Delphi process allowed patients and healthcare practitioners to individually rate the outcomes in terms of impor-tance on a 9-point Likert scale.Results: After 2 rounds of the iterative eDelphi process, the initial outcomes were distilled down to a final COS including sub-jective questions (visual analogue scores, quantitative and qualitative), quality of life measures, psychophysical testing of smell, baseline psychophysical testing of taste, and presence of side effects along with the investigational medicine/device and patient's symptom log.Conclusions: Inclusion of these core outcomes in future trials will increase the value of research on clinical interventions for OD.We include recommendations regarding the outcomes that should be measured, although future work will be required to further develop and revalidate existing outcome measures.