Examples
Worked examples
- Is an instance
A UK university sponsors a randomised trial of a physiotherapy intervention. Before recruiting the first participant, the trial team submits the required data set to isrctn.com and receives ISRCTN14567890 as its permanent trial identifier, which then appears on the participant information sheet, the funding application, and eventually the results publication.
- Is an instance
A multi-country drug trial with a UK coordinating centre and US sites registers on both ISRCTN and ClinicalTrials.gov (dual registration) so that US-based investigators satisfy the FDAAA 801/NIH ClinicalTrials.gov requirement while the UK sponsor satisfies funder and HRA (Health Research Authority) expectations for a UK-led study; the two records cross-reference each other's identifiers, and the WHO ICTRP indexes both under the same trial.
Counter-examples
Looks similar, but isn't
- Not an instance
A hospital's internal trial-tracking spreadsheet, used only to log ongoing studies for local governance purposes, is not an ISRCTN registration — it is not publicly searchable, was not submitted through isrctn.com, and does not carry a WHO ICTRP-recognised identifier. Only submission through the actual ISRCTN registry (or another WHO-recognised primary registry) produces a registration that satisfies journal, funder, or regulatory registration requirements.
Editorial commentary
What ISRCTN is
ISRCTN is a clinical study registry originally built around the International Standard Randomised Controlled Trial Number scheme, now operating under the simplified name “ISRCTN — the UK’s clinical study registry.” It is owned by the non-profit ISRCTN company and administered by BioMed Central Ltd (part of Springer Nature) on the company’s behalf. Registration is free to the submitting researcher. A registered study receives a permanent ISRCTN number that never changes and remains publicly resolvable even if the study is later withdrawn or terminated — the record is retained with its status updated, not deleted.
Who administers ISRCTN, and its regulatory standing
ISRCTN is one of the WHO International Clinical Trials Registry Platform (ICTRP)’s recognised primary registries, alongside ClinicalTrials.gov, the EU’s CTIS, ANZCTR, CTRI, ChiCTR, DRKS, JPRN and others — each primary registry independently meets the WHO’s data-quality and public-access criteria, and records are pooled into the WHO’s global search portal without requiring separate registration with WHO itself. ISRCTN is also recognised by the International Committee of Medical Journal Editors (ICMJE) as an acceptable registry for journals that require prospective trial registration as a condition of publication (the ICMJE’s Uniform Requirements accept registration with any WHO ICTRP primary registry, not ClinicalTrials.gov specifically). Records are also indexed in MEDLINE/PubMed.
ISRCTN vs. ClinicalTrials.gov
ISRCTN and ClinicalTrials.gov are separate, independently operated registries that both satisfy WHO ICTRP and ICMJE registration requirements, but they are not interchangeable for every purpose:
- Legal/regulatory driver. ClinicalTrials.gov registration and results reporting is a US federal requirement under FDAAA 801 (42 CFR Part 11) for applicable clinical trials, and a separate NIH policy requirement for NIH-funded trials. ISRCTN has no directly equivalent US-style statutory reporting mandate; UK sponsors register with it primarily to satisfy funder policies, HRA/REC expectations, and journal/ICMJE registration requirements.
- Administering body. ClinicalTrials.gov is operated by the US National Library of Medicine (part of NIH); ISRCTN is administered by BioMed Central/Springer Nature on behalf of the non-profit ISRCTN company — a commercial-publisher-adjacent operator rather than a government agency, though both are WHO-recognised primary registries with equal standing under WHO ICTRP and ICMJE rules.
- Typical registrant base. ClinicalTrials.gov is the default choice for US-sponsored or US-regulated trials; ISRCTN is the default for UK-sponsored trials and is also used internationally, particularly for publicly funded trials run by UK-linked consortia or NIHR-funded programmes.
- Dual registration. Multi-country trials with both UK and US sites, or US-sponsored trials with UK coordinating centres, frequently register on both platforms — each satisfies a different jurisdiction’s requirement, and each record typically cross-references the other’s identifier so the WHO ICTRP can de-duplicate them into a single indexed trial.
When and why a trial uses ISRCTN
Investigators and sponsors register with ISRCTN specifically (rather than, or in addition to, another primary registry) when one or more of the following apply: the trial is UK-sponsored or UK-coordinated; a UK funder (for example, NIHR) requires registration with a WHO-recognised registry and ISRCTN is the sponsor’s institutional default; the study is a non-randomised interventional or observational health-intervention study that ISRCTN’s broadened scope accommodates; or the target journal requires prospective registration per ICMJE policy and the sponsor’s existing infrastructure is built around ISRCTN. As with any prospective registration, the practical purpose is the same regardless of which primary registry is used: create a public, time-stamped, pre-results record of the study’s design and pre-specified outcomes so that publication bias and outcome-switching are detectable after the fact, and so systematic reviewers and other researchers can find ongoing and completed studies on a given question. This is the same underlying logic behind PROSPERO registration for systematic-review protocols, applied to primary clinical studies rather than evidence synthesis.
Related CASRAI resources
See ClinicalTrials.gov for the equivalent US registry, Clinical Trial Registration for the general concept independent of any specific registry, PROSPERO Registration for the systematic-review-protocol equivalent, and the guide on clinical trial registration and reporting compliance for the fuller compliance picture, including FDAAA 801 and ICMJE requirements.
Machine-readable encodings
Use in your systems
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