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 importance 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 subjective 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.

2nd ORL Department Aristotle University Thessaloniki Greece

5th Sense UK Charity Bicester United Kingdom

Department of Anatomy Universitat du Quebec a Trois Rivieres Canada

Department of Biomedicine Aarhus University Denmark

Department of Otolaryngology Head and Neck Surgery Indiana University School of Medicine Indiana

Department of Otolaryngology Massachusetts Eye and Ear Infirmary Harvard Medical School Boston MA USA

Department of Otorhinolaryngology and Head and Neck Surgery Regional Hospital and University of Pardubice Czech Republic; Department of Otorhinolaryngology and Head and Neck Surgery Regional Hospital and Faculty of Heath Studies University of Pardubice Czech Republic

Division of Surgery and Interventional Science and UCL Cancer Institute University College London and Barts Health NHS Trust United Kingdom

ENT University of Insubria Italian Academy of Rhinology Varese Italy

Flavour Clinic University Clinic for Flavour Balance and Sleep Department of Otorhinolaryngology Regional Hospital Godstrup Denmark

James Paget University Hospital Great Yarmouth United Kingdom

Rhinology Unit and Smell Clinic Hospital Clinic Barcelona IDIBAPS Universitat de Barcelona CIBERES Barcelona Catalonia Spain

Section of Otolaryngology Head and Neck Surgery The University of Chicago Chicago IL USA

Smell and Taste Clinic Department of Otorhinolaryngology Technische Universitat Dresden Dresden Germany

References provided by Crossref.org

The Development and Validation of the Smell-Qx Questionnaire, Based on a Systematic Review of the Literature and the COMET Initiative on the Development of Core Outcome Sets for Clinical Trials in Olfactory Disorders