Each core outcome must be assessed using a valid and reliable instrument. In this next phase of the GenderCOS project, we are identifying appropriate outcome measurement instruments (OMIs) for each of the included outcomes in genital gender-affirming surgery. The selection of OMIs is based on:

·         Validity and reliability, especially for transgender and gender diverse people

·         Relevance to the gender-affirming surgical context

·         Feasibility and burden of implementation

Now that the core outcomes are finalized, the next step is to determine how to measure each outcome consistently. An OMI is a standardized tool or method - such as a questionnaire, physical examination, or imaging technique - used to assess whether an outcome is present and to what extent. OMIs are essential to ensure consistency and comparability in clinical research as they ensure standardization in the assessment of core outcomes.

We are also determining when each outcome should be assessed post-surgery. This depends on:

• Expected timing of complications (e.g., early vs. late)

• Timing of patient recovery and adaptation

• Feasibility of long-term follow-up in clinical studies

When selecting the appropriate time of assessment for research purposes we should consider the sensitivity of outcome detection along with its feasibility for implementation in research.

Many transgender and gender diverse individuals wish to undergo genital gender surgery as part of their gender affirming treatment. A variety of procedures and techniques for genital surgery are currently available. Options for feminizing surgery surgical are: vaginoplasty, vulvoplasty, labiaplasty, and clitoroplasty. For masculinizing genital gender surgery options are: phalloplasty, metoidioplasty, scrotoplasty and coronaplasty. For each of these procedures, several different surgical techniques are used.

Clinical research is important because it provides evidence on the benefits, effectiveness, and safety of the various surgical treatments. This knowledge is vital to be able to select the best treatment option for each individual.

It is increasingly recognised that involvement of the population concerned is essential. Otherwise, studies may not evaluate what really matters to the population.

Current research in the field of gender surgery is mostly about the safety and “success” of one specific surgical procedure, where “success” is defined in various ways. For instance, studies may report on sexual aspects or aesthetic outcomes. Also, when studies report on safety, diverse outcomes are measured. Presently, no consensus exists on the definitions of outcomes or on which measurement instruments should be used. This hinders comparison between studies and the advancement of knowledge.

To be able to compare procedures or techniques, outcomes measured in different studies should be comparable; which a COS can aid.

A Core Outcome Set is a standardized limited list of the most important outcomes that researchers should measure and report in all clinical studies concerning – in this case – genital gender surgery. The outcomes lists for feminizing and masculinizing genital surgery will naturally be different. They will be developed by the same methods but with different stakeholders. The outcomes must be relevant to the population, and there must be consensus about the definitions and the way they are measured.

When all researchers at the very least report on these standardized and most important outcomes, measured in the same way, we can compare and combine outcomes of different clinical studies and draw meaningful conclusions. Off course, researchers can always include extra outcomes in their studies. When research can be combined and compared, the quality of scientific evidence backing up guidelines and shared decision making, improves.

The GenderCOS project will develop two Core Outcome Sets:

1) A COS for feminizing genital gender surgery;

2) A COS for masculinizing genital gender surgery.

Development of a COS has three stages. In all stages participation of the transgender and gender diverse community and healthcare professionals is essential.

1. All possible outcomes are collected from clinical research and from interviews and focus groups with transgender and gender diverse people. A list of possible outcomes is drawn.

2. Experts by lived experience and professionals in the field of genital surgery form all over the world are invited to prioritize the outcomes in multiple rounds. Through analyses of the input the list is shortened over each round.

3. Consensus about the COS is reached through a consensus meeting in which all stakeholders are represented.