Protocol for the development of a Core Outcome Set for Inherited Ichthyosis (COSII).

Introduction Inherited ichthyosis comprise a group of rare keratinization disorders caused by abnormal epidermal barrier function. Ichthyosis is yet incurable and current treatments mainly focus on alleviating symptoms such as scaling, erythema and pruritus. Recent developments show promising results for interventions based on the immune-phenotype like biologicals or pathogenesis-based therapies such as gene therapy. However, the lack of uniform reporting and variety of treatment outcomes may complicate performing and comparing efficacy studies. The core outcome set for inherited ichthyosis (COSII) aims to develop a core outcome set (COS), i.e. the minimum of outcomes that should be measured and reported in effectiveness research, including a minimum set of baseline characteristics. Methods The COSII project will follow the guidelines from the Core Outcome Measures in Effectiveness Trials (COMET) initiative including the Core Outcome Set-STAndards for Development (COS-STAD) recommendations and the Core Outcome Set Standardised Protocol (COS-STAP) checklist. The COS development methodology, including this protocol, follows guidance of the CHORD COUSIN Collaboration 'C3'. The first stage of this project involves identifying a possible list of outcomes through performing a scoping literature review and conducting interviews with patient(s) (representatives). This list will be presented to five different stakeholders groups: healthcare professionals, researchers, patient(s) (representatives), industry representatives and regulators. All stakeholders will rate the importance of each outcome in a three-round eDelphi survey. Ultimately, a virtual consensus meeting will be convened to finalize the COS. Ethical approval was obtained prior to the start of this project from the Medical Ethics Committee board at Maastricht University Medical Centre (METC 2022-3192). Informed consent will be asked prior to enrolment in the eDelphi. This study is registered with the COMET. The results will be distributed via a peer-reviewed journal, communicated to all relevant parties and showcased at national and international conferences. Conclusion This will be the first COS for inherited ichthyosis research in accordance with the Core Outcome Measures in Effectiveness Trials initiative. The development of a COS aims to improve consistency of reporting and the heterogeneity of outcomes in ichthyosis research.