The GenderCOS project: study protocol for the development of two international Core Outcome Sets for genital gender affirming surgery

Background: Worldwide an increasing number of transgender and gender diverse individuals are requesting genital Gender Affirming Surgery (gGAS). For both masculinizing and feminizing gGAS various procedures and techniques are employed. Current literature on gGAS reports heterogeneous, non-standardized and often ill-defined outcomes. Presently, no consensus exists on what outcomes should be evaluated in order to assess the clinical results and the effectiveness of these procedures, which precludes development of evidence-based treatment guidelines. Aims: This international consensus study aims to develop Core Outcome Sets (COS) for both masculinizing and feminizing gGAS. These represent the minimum sets of outcomes recommended to be measured and reported in all clinical trials pertaining to gGAS. Methods: Two Core Outcome Sets for masculinizing and feminizing gGAS will be developed in parallel by following the Core Outcome Measures in Effectiveness Trials (COMET) guidelines. The stages of development for each set are: i) Identify outcomes measured and reported in previous research through a systematic review of the literature; ii) Identify outcomes suggested by transgender and gender diverse individuals during focus groups and interviews; iii) Combine and structure the outcomes into a preliminary outcome list; iv) Conduct e-Delphi surveys among stakeholders (i.e. professionals in transgender healthcare and transgender individuals) in which all potential outcomes will be rated on level of importance; and v) Decide on the final COS during an online consensus meeting. Discussion: This study will produce minimum, core sets of relevant outcomes for gGAS, through reaching international consensus with key stakeholders, including transgender individuals. Development of these COS will enable the measurement and reporting of relevant and standardized outcomes, facilitating continued scientific advancement of this field.