ISRCTN: Frequently asked questions

The ISRCTN scheme has been in existence since March 2000, when numbers were initially issued in a pilot phase to trials sponsored by the Medical Research Council in the UK.  The scheme was formally launched in May 2003 as ‘the first online service that provides unique numbers to randomized controlled trials in all areas of healthcare and from all countries around the world’.
Please email the ISRCTN office at info@isrctn.com for any record harvesting questions.
The following FAQs are intended to provide further information about the ISRCTN scheme.

Q. What does ISRCTN mean?
A. ISRCTN stands for International Standard Randomised Controlled Trial Number.  The ISRCTN scheme is a simple numeric system for the unique identification of clinical trials worldwide. In addition to randomised controlled trials, the ISRCTN Register will also accept registration of other forms of studies designed to assess the efficacy of healthcare interventions. 

Q. What is the aim of the ISRCTN scheme?
A. The aim of the ISRCTN scheme is to simplify the identification of trials and provide a unique number that can be used to track all publications and reports resulting from each trial.

Q. Who owns the ISRCTN Register?
A.  The ISRCTN Register is owned by ISRCTN - a not-for-profit organisation.

Q. Does the ISRCTN Register comply with the requirements set out by the International Committee of Medical Journal Editors in their September 2004 and May 2005 editorials?
A.  Yes. The ISRCTN Register complies with all the criteria set out in the ICMJE editorials.

Q. Does the ISRCTN Register comply with the proposed WHO registration data set?
A.  Yes. The ISRCTN Register complies with all the fields proposed in the WHO registration data set.

Q. What is meant by the term 'randomised controlled trial' (RCT)?
A. A clinical study in which two (or more) forms of care are compared, and in which the participants are allocated to one of the forms of care in the study, in an unbiased way, by using the play of chance.
more

Q. What trials are eligible for an ISRCTN?
A. Trials should either be RCTs or studies designed to assess the efficacy of healthcare interventions.

Q. Who is responsible for obtaining an ISRCTN?
A. It is recommended that the trial sponsor applies for an ISRCTN, as trial registration is often regarded as being the responsibility of the sponsor. However it is also possible for trial coordinators and/or investigators to apply. In particular, in the case of self-funded trials, the lead principal investigator (i.e. the individual named on the protocol with overall legal and scientific responsibility for the trial) should apply. It is expected that all trials have a sponsor, and applicants will be asked to fill in sponsor details in the application form. In the case of self-funded trials, the sponsor is likely to be the organisation where the lead principal investigator carries out the research. If the sponsor is not finalised at the time of the application, applicants are advised to enter, for example, ‘Sponsor not defined’.

Q. When should a trial be registered?
A. A trial can be registered at any stage during its development. It is never too late or too early to register a trial. Trialists are encouraged, however, to register before patient enrolment begins.

Q. Should pilot studies be registered?
A. Although not all pilot studies go on to become full trials, we recommend that pilot studies should be registered provided the study is designed to assess the efficacy of a healthcare intervention(s).

Q. What happens when the pilot study becomes the main study?
A. If the pilot study has already received an ISRCTN, there is no need to make a new submission as long as the main study has the same participant(s) and intervention(s). A new ISRCTN is required if the trial will be studying different groups of patients (i.e. not the same participant[s] and intervention[s] as in the pilot study).

Q. How do I decide whether the trial requires more than one ISRCTN?
A. If the trial involves more than one randomisation but is regarded as a single trial by the sponsor, it requires only one number. However, if the trial involves separate randomisations for different types of participant(s), each part can be numbered separately. In this case, an ISRCTN will be assigned for each part, and investigators should ensure that the correct ISRCTN is used for the relevant part of the trial.

Q. How should you use the ISRCTN?
A. The ISRCTN is a randomly generated, 8-digit number, prefixed by the code, ISRCTN, that will uniquely identify your trial within the ISRCTN system. Where practical, this number should be used in all aspects of trial management, documentation and publication. It should be referenced in all new material relating to the trial, used in correspondence and reports (e.g. Data Monitoring Committee reports) and in any academic/journal publications (preferably in the title if this is acceptable to the journal, as this will allow it to be more readily identified through Medline, PubMed, Current Contents, etc.).

If the trial is registered in a specialist trial register, the ISRCTN should be quoted there. This will allow those using registers to identify quickly and reliably any overlap between registers.

The ISRCTN should be retained, even if there are alterations to the protocol, the investigators or the funding body.

Q. How should you cite the ISRCTN?
A. The unique number for each trial has the following form:

ISRCTNXXXXXXXX

Where XXXXXXXX represents the unique number, always prefixed by 'ISRCTN'. Please note that there is no space between the prefix 'ISRCTN' and the number.

Q. What happens if a duplicate ISRCTN is assigned?
A. In the event that a trial has been assigned more than one ISRCTN (for example if it has been registered by two or more separate organisations/individuals), the following rules would be applied:

• Check with the lead principal investigator which number has been most commonly used OR
• Use the ISRCTN number assigned first

Should any change take place, all relevant parties would be informed. ISRCTNs that are taken out of use will not be re-assigned to another trial.

Q. What is the ISRCTN Register?
A. The ISRCTN Register is a database of trials with ISRCTNs. It provides a basic set of data items about each trial supplied by the sponsor or lead principal investigator.

Q. What is the relationship between the ISRCTN Register and Current Controlled Trials Ltd
A.  The ISRCTN Register is owned by ISRCTN - a not-for-profit organisation.  Current Controlled Trials Ltd. administers the scheme on behalf of ISRCTN..

Q. What is the relationship between the metaRegister of Controlled Trials and the ISRCTN Register?
A. The metaRegister and the ISRCTN Register are two separate registers.

Q. What if my trial is sponsored by an organisation that is included in the metaRegister of Controlled Trials?
A. The sponsor or lead principal investigator should check with the register holder directly if an ISRCTN has been or will be requested for their trial. If not, the sponsor or lead principal investigator may contact the ISRCTN office directly.

Q. How do I obtain an ISRCTN?
A. It is possible to apply for an ISRCTN online using the ISRCTN application form. ISRCTNs may also be obtained by contacting the ISRCTN office directly.

Q. What information do I need to provide to obtain an ISRCTN?
A. The list of data items that MUST be supplied is available.

May 2007