Methodology · Last reviewed 2026-05-16
Methodology
Summary
This site is a critical research project — not neutral, but source-faithful. Our conclusions arise from an evidence-based weighing of the available evidence, not from a predetermined position. Sources are stratified according to GRADE principles: independent systematic reviews weigh more heavily than publications from the original clinic. Where the evidence is unambiguously weak — as concluded by NICE, SBU and Cass — we name that unambiguously.
1. Source hierarchy
Sources on this site are stratified according to an adapted pyramid of evidence-based medicine. In decreasing priority:
| Level | Source type | Example |
|---|---|---|
| 1 | Independent systematic reviews, HTA reports | SBU 2022, Cass Review 2024 |
| 2 | Randomised controlled trials | (no RCTs known in this domain — which is itself a conclusion) |
| 3 | Cohort and follow-up studies from independent groups | Carmichael 2021 (GIDS) |
| 4 | Cohort and follow-up studies from the original clinic | de Vries et al. 2014, van der Loos 2022 |
| 5 | Clinical guidelines on independent evidence | COHERE 2020, NICE evidence reviews 2020 |
| 6 | Clinical guidelines on consensus basis | Endocrine Society 2017, WPATH SOC-8 |
| 7 | Peer-reviewed critiques and methodological analyses | Biggs 2022, Levine et al. 2022 |
| 8 | Case reports and case series | Cohen-Kettenis & van Goozen 1998 |
| 9 | Non-peer-reviewed but publicly documented | WPATH Files, court rulings |
Explanation: publications of the original research group (VUmc / Amsterdam UMC) weigh less than independent replication or evaluation, because there is demonstrable conflict of interest — institutional and reputational — in interpreting the outcomes of one's own treatment practice.
2. Citation style
Footnotes follow Vancouver style: numbered in order of first appearance, with authors, title, journal, year, volume, page range and — where available — DOI or PubMed identifier. For reports without DOI: publisher, year and archived URL.
3. Weighing of conflicting sources
When sources contradict each other, both positions are presented with explicit attribution. We do not "choose sides" between primary sources — but we do weigh. In case of conflict between an independent systematic review and a publication from the original clinic, the systematic review takes priority. Methodological differences (sample, follow-up, definition of outcome measures, conflict of interest statements) are made explicit so that readers can follow the judgment.
4. What determines our tone
Where the external evidence is unambiguous — for example that the Dutch Protocol rests on evidence of "very low certainty" according to GRADE — we describe that in unambiguous terms. We do not maintain an artificial balance between claims made by a single research group and an international chorus of independent evaluators. That is not activism; that is correct weighing of evidence.
5. Updates
Pages are reviewed at least annually. When a new HTA report, a new guideline version or relevant peer-reviewed publication appears, the relevant page is updated within four weeks. Last reviewed refers to the most recent substantive check.
6. Exclusions
The following source types are not used as factual sources:
- Anonymous blogs and social media posts.
- Press releases without underlying publication.
- Material from advocacy organisations without independent verification.
- Non-public internal documents.
By exception, such documents may be cited as subject of the debate (e.g. the WPATH files), with explicit mention of the nature of the document.