Today is 2023-01-29

Frequently Asked Questions

● What is a clinical trial?

For the purposes of registration, a clinical trial is any study that prospectively assigns human participants or groups of humans to one or more health-related interventions to evaluate the effects on health outcomes. Clinical trials may also be referred to as interventional trials. Interventions include but are not restricted to drugs, cells and other biological products, surgical procedures, radiologic procedures, devices, behavioural treatments, process-of-care changes, preventive care, etc. This definition includes Phase I to Phase IV trials.

● Which trials should be registered?

All clinical trials meeting the above definition should be registered. Thus, early and late trials, trials of marketed or non-marketed products, randomized or non-randomized trials -- all should be registered.

● What is the difference between a clinical trials register and a clinical trials registry?

A clinical trials register is the formal record of an internationally agreed minimum amount of information about a clinical trial. This record is usually stored in and managed using a database. A clinical trials registry is the entity that houses the register, and is responsible for ensuring the completeness and accuracy of the information it contains, and that the registered information is used to inform health care decision making. A clinical trials registry is more than its database.

● Why register clinical trials?

Please read this page

● Who is responsible for registering a trial?

The "Responsible Registrant".

● When should trials be registered?

Trials should be registered before the first participant is recruited.

● Can I register with the WHO ICTRP?

No, WHO does not maintain its own registry so you cannot register your trial directly with WHO ICTRP.

How to Register a Trial

● What information needs to be registered?

The minimum information that must be registered is specified in the WHO Trial Registration Data Set. Individual registers may request more information than this (e.g., study sites).

● Are there software or hardware specifications that should be followed for building a trial registry?

Yes, please contact WHO ICTRP.

● How many times should a trial be registered?

To meet WHO requirements for transparency and publication it is only necessary for your trial to be to registered once, in either a Primary Registry or an ICMJE approved registry.

● How to cite a record on a clinical trials register


:: Please read this document [pdf 26kb]


● When to cite a record on a clinical trials register

The registry record will be the only publicly available document on a trial until results from the trial are published. Some examples of situations when studies might be quoted are:

  • When a manuscript reporting the results of the trial is published or otherwise reported
  • When a manuscript reporting methodological issues relating to a particular trial are published or otherwise reported
  • In protocols to systematic reviews, or in completed systematic reviews (e.g. when a list of ongoing trials are included)
  • In protocols to prospective meta-analyses, which will list the ongoing trials to be included
  • In any manuscript when reference to an ongoing or unpublished (or even published) trial might be relevant
  • ● What is trial registration?

    WHO regards trial registration as the publication of an internationally-agreed set of information about the design, conduct and administration of clinical trials. These details are published on a publicly-accessible website managed by a registry conforming to WHO standards.