Core Outcome Sets & measurement instruments for masculinizing and feminizing genital gender-affirming surgery
The Core Outcome Sets and Outcome Measurements instruments are available for use!
The GenderCOS projects developed Core Outcome Sets (COS) for feminizing and masculinizing gGAS, The final COS include 20 outcomes overall, including patient-reported outcomes, clinical outcomes and adverse events. These outcome sets were developed through systematic literature reviews, qualitative interviews with transgender and gender-diverse individuals, a multi-round Delphi study, and a consensus meeting. The Outcome Measurement Instruments (OMI) for 19 of 20 unique core outcomes were established through a consensus process among professional experts in gender-care.
Publications
Outcome measurement instruments of both COS
Angelini M, Roijer PJ, Vallinga MS et al. Outcome measurement instruments for the core outcome sets on genital gender-affirming surgery: the GenderCOS project. EClinicalMedicine. 2026 Apr 18;95:103907. 10.1016/j.eclinm.2026.103907.
Core Outcome Sets
Vallinga MS, Roijer PJ, Pidgeon TE et al. The core outcome set for studies on feminizing genital gender-affirming surgery: findings from the GenderCOS project. EClinicalMedicine. 2025 Jul 1;85:103323. 10.1016/j.eclinm.2025.103323
Roijer PJ, Vallinga MS, Pidgeon TE et al. A core outcome set for research on masculinizing genital gender-affirming surgery: international consensus results from the GenderCOS project. EClinicalMedicine. 2025 Jul 1;85:103325. 10.1016/j.eclinm.2025.103325.
Protocol
Roijer PJ, Vallinga MS, Pidgeon TE et al. The GenderCOS project: study protocol for the development of two international Core Outcome Sets for genital gender affirming surgery. Int J Transgend Health. 2023 Dec 15;26(1):78-87. 10.1080/26895269.2023.2288881.
Contact us
If you would like to find out more, please contact gendercos@amsterdamumc.nl
Final GenderCOS
Download the two full COS including definitions here: Full COS
Download OMI checklist here: GenderCOS OMI
Inclusivity
&
Terminology
The GenderCOS project is committed to inclusivity and using respectful language and terminology. Please be aware that while we strive to use inclusive terminology whenever possible, we often opt for umbrella terminology for the sake of readability. "Transgender" and "gender diverse" are umbrella terms used to describe people with gender identities and/or expressions that are different from their sex assigned at birth. This may include, but is not limited to, people who identify as trans, nonbinary, gender nonconforming, agender, and others who do not identify as cisgender. By feminizing genital gender affirming surgery, we also mean de-masculinizing genital gender affirming surgery. By masculinizing genital gender affirming surgery, we also mean de-feminizing genital gender affirming surgery. The description "feminizing" (and "de-masculinizing") and "masculinizing" (and "de-feminizing") pertains to a type of surgical intervention, rather than directly implying anything about someone’s gender identity.
To ensure that the first two Core Outcome Sets developed in the GenderCOS study are specific and feasible, the scopes of these Core Outcome Sets have been limited to surgical techniques for genital feminization and masculinization. However, we recognize that there are other surgical options for genital affirming surgery available and/or performed. These surgeries may be included in future editions of the GenderCOS for genital surgery and may require a separate core set of outcomes.
If you have any questions or want to help us improve our inclusivity efforts, please reach out to us via gendercos@amsterdamumc.nl.
The GenderCOS project Team
To ensure that the Core Outcome Sets are representative and will be usefull worldwide, we have assembled an international team of experts. Our steering team is formed by junior researchers, professionals working in gender care and two population representatives.