Evidence Family
Menu

Provenance

Clinical trial registration explained

Last checked 7 November 2026 · 6 sources

Short answer

Trial registration creates a public record of a study before results exist, so later reports can be checked against it. ICMJE journals require registration at or before first patient consent, in a WHO primary registry or ClinicalTrials.gov, with a 24-item data set 1. The WHO network lists 18 primary registries 2. US rules require registration within 21 days of first enrolment and results within one year of primary completion 3,4. The EU requires a results summary within one year of the end of a trial 5.
ICMJE timing
At or before first patient consent for enrolment 1
Minimum data set
24 items 1
WHO primary registries
18 listed 2
US registration deadline
21 calendar days after the first subject is enrolled 3
US results deadline
1 year after the primary completion date 4
EU results deadline
Within one year from the end of the trial in all Member States concerned 5

What registration is for

ICMJE says registration aims to prevent selective publication and selective reporting of outcomes, prevent unnecessary duplication of research, tell patients which trials are open, and give ethics boards a view of similar work 1. It says retrospective registration, for example at manuscript submission, meets none of these purposes 1.

For provenance, the registration number links every report of one trial. Cochrane lists trial registration numbers first among the most useful criteria for linking multiple reports of the same study 6.

The ICMJE rule

  • Editors should require registration in a public registry at or before the time of first patient consent for enrolment, as a condition of considering a paper 1.
  • ICMJE uses the date registration materials were first submitted to a registry as the registration date 1.
  • Acceptable registries are WHO ICTRP primary registries with the 24-item data set, or ClinicalTrials.gov, a data provider to the ICTRP 1.
  • Registrations missing any of the 24 fields, or not public, such as phase I trials submitted to the EU's CTIS and device trials held in a lock box, are inadequate 1.
  • Journals should publish the registration number at the end of the abstract 1.
  • Manuscripts reporting trial results submitted from 1 July 2018 must contain a data sharing statement, and trials enrolling from 1 January 2019 must include a data sharing plan in the registration 1.

Deadlines by jurisdiction

JurisdictionRegistrationResultsSource
United StatesNot later than 21 calendar days after the first human subject is enrolled, for applicable clinical trials 3No later than 1 year after the primary completion date, with set delays allowed by certification 442 CFR 11.24 and 11.44 3,4
European UnionAll trials registered in the EU database before they start, per the recitals 5Summary of results and a lay summary within one year from the end of the trial in all Member States concerned 5Regulation (EU) No 536/2014 5
European UnionStart of trial notified within 15 days 5Clinical study report within 30 days after a marketing authorisation decision, where relevant 5Regulation (EU) No 536/2014 5
ICMJE journalsAt or before first patient consent 1Registry results limited to an abstract or tables are not prior publication 1ICMJE Recommendations 1

The WHO primary registries

WHO says primary registries meet criteria for content, quality and validity, accessibility, unique identification, technical capacity and administration, and meet ICMJE requirements 2. The list read names 18 registries 2. They include the Australian New Zealand Clinical Trials Registry, the Brazilian Clinical Trials Registry, the Chinese Clinical Trial Registry, Korea's Clinical Research Information Service, the EU's Clinical Trials Information System and EU Clinical Trials Register, Clinical Trials Registry India, Germany's DRKS, ISRCTN, the Japan Registry of Clinical Trials and the Pan African Clinical Trial Registry 2.

How to use a registry record when checking a study

  • Find the registration number in the abstract or methods 1.
  • Compare the registration date with the enrolment start. ICMJE treats the first submission date as the registration date 1.
  • Compare the planned outcomes with the published ones. ICMJE says authors, not editors, must explain discrepancies between registry results and journal publications 1.
  • Check whether results were posted on time under the US or EU rule that applies 4,5.
  • Treat secondary analyses as part of the parent trial. ICMJE says they should cite the primary trial's registration number, not register as separate trials 1.

Common questions

Which registries does ICMJE accept?

WHO ICTRP primary registries with the 24-item data set, and ClinicalTrials.gov as a data provider to the ICTRP 1.

How long do US sponsors have to register a trial?

Not later than 21 calendar days after the first human subject is enrolled, for applicable clinical trials 3.

When must EU trial results be posted?

A summary of results is due within one year from the end of the trial in all Member States concerned, with a lay summary 5.

Does posting results in a registry count as prior publication?

Not if limited to a brief structured abstract or tables, according to ICMJE 1.

Rules and charges change. Check the official source linked on this page before you pay or travel. Spotted an error? Email hello@evidencefamily.com.

Sources

  1. ICMJE: Recommendations, Clinical Trials
  2. World Health Organization: Primary registries (ICTRP Registry Network)
  3. Cornell Law School LII: 42 CFR § 11.24, When must clinical trial registration information be submitted?
  4. Cornell Law School LII: 42 CFR § 11.44, When must clinical trial results information be submitted for applicable clinical trials subject to § 11.42?
  5. EUR-Lex: Regulation (EU) No 536/2014 of the European Parliament and of the Council of 16 April 2014 on clinical trials on medicinal products for human use
  6. Cochrane: Cochrane Handbook for Systematic Reviews of Interventions, Chapter 5, Collecting data

Related