WHO International Clinical Trials Registry Platform (ICTRP)

What WHO ICTRP is

The WHO International Clinical Trials Registry Platform (ICTRP), initiated by the World Health Organization in 2000, is best understood as a registry of registries: a global search portal and aggregation platform sitting above a network of independently operated national and regional ‘primary registries,’ rather than a registry a trial registers with directly. Each primary registry — ClinicalTrials.gov, the EU’s Clinical Trials Information System (CTIS), ISRCTN, ANZCTR, India’s CTRI, China’s ChiCTR, Germany’s DRKS, Japan’s JPRN, and others — independently meets WHO’s own registry-quality criteria (free public access, electronic searchability, not-for-profit operation, and capture of the WHO Trial Registration Data Set) and sends regular data feeds to ICTRP.

What it aggregates, and how registration works

A trial registers once, with a single primary registry of the sponsor’s choosing — not with WHO directly — and is then automatically pooled into ICTRP’s searchable database via that registry’s data feed. This design means a researcher searching ICTRP’s own portal can find trials across every recognized primary registry in one search, including trials registered in countries or registries they might not otherwise think to check individually.

Relationship to ClinicalTrials.gov

ClinicalTrials.gov, operated by the US National Library of Medicine, is one primary registry among the roughly fifteen WHO currently recognizes — it is the largest and most frequently cited, but it is not the only one, and it is not synonymous with WHO ICTRP itself. Many trials, particularly those sponsored outside the United States, are registered exclusively with a non-US primary registry and are discoverable through ICTRP’s search portal without ever appearing in ClinicalTrials.gov. Searching ClinicalTrials.gov alone is not equivalent to a comprehensive trial-registry search.

Why it matters for prospective-registration compliance

The International Committee of Medical Journal Editors (ICMJE) accepts registration with any WHO ICTRP primary registry — not exclusively ClinicalTrials.gov — as satisfying its requirement for prospective clinical trial registration as a condition of publication. This is distinct from the US-specific statutory reporting obligations under FDAAA 801, which apply only to ClinicalTrials.gov for applicable clinical trials. See CASRAI’s clinical trial registration entry for the underlying general concept, and the clinical trial registration and reporting compliance guide for how the ICMJE, FDAAA 801, and NIH requirements fit together.

Why it matters for systematic-review searching

Systematic review and evidence-synthesis methodology, including Cochrane and PRISMA-aligned guidance, recommends searching trial registries — WHO ICTRP among them — as part of a comprehensive search strategy, to surface both completed-but-unpublished and still-ongoing trials that a literature-database search alone would miss. This is one of the concrete ways reviewers try to mitigate publication bias in a synthesis, alongside grey-literature searching. See CASRAI’s searching grey literature for a systematic review guide and research registries guide for where ICTRP fits into a broader search strategy.