Clinical trials
Why search for clinical trials?
An important category of grey literature, particularly for clinical research, is clinical trials. While many trials are reported in the published literature and can be located via Cochrane Central Register of Controlled Trials (CENTRAL), others are unpublished or ongoing. Searching registers for ongoing trials and trials with negative results is critical.
Finding out about unpublished studies and including them in a systematic review, when eligible and appropriate, is important for minimising bias. Ongoing trials should be identified and tracked for possible inclusion in reviews on completion.
Registers will not include records for all trials conducted as this is not always a legal obligation, however in many cases registration is required under organisational, funding, legal or publisher requirements.
- Australian Clinical TrialsAustralian Government site providing a range of information and links for researchers, clinicians and participants, including lists of Australian trials registries.
Clinical trial registers
World Health Organization's International Clinical Trials Registry Platform
Includes records from many key registers from around the world, including among others:
- Australian New Zealand Clinical Trials Registry (ANZCTR)
- Clinical Trials.gov (Unites States)
- EU Clinical Trials Register (EU-CTR)
You may find there are advantages to searching individual registers as these will have more sophisticated search functionality and will be more current (some months may have elapsed since the last load of records to ICTRP) .
- WHO International Clinical Trials Registry PlatformProvides access to a central database containing trial registration data sets provided by a variety of registries from around the world (including among others Australia, China, USA, the EU, and Japan). Links out to the full original records. Options to search or to browse by topic/country/region. Search original registries for most up-to-date results
Australian New Zealand Clinical Trials Registry (ANZCTR)
- ANZCTR (Australian New Zealand Clinical Trials Registry)The ANZCTR is a Primary Registry in the World Health Organisation (WHO) Registry Network. It accepts trials for registration from all countries and '...from the full spectrum of therapeutic areas of pharmaceuticals, surgical procedures, preventive measures, lifestyle, devices, treatment and rehabilitation strategies and complementary therapies' - 'About us'
Clinical Trials.gov
- ClinicalTrials.govA registry and results database of publicly and privately supported clinical studies (primarily trials) conducted in the United States and around the world. Maintained by the National Library of Medicine. Records provide summary information including disease/condition, intervention, study design, participant eligibility criteria, contact information and more
European Union Clinical Trials Register
- European Union Clinical Trials Register'The European Union Clinical Trials Register allows you to search for protocol and results information on:
- interventional clinical trials that are conducted in the European Union (EU) and the European Economic Area (EEA);
- clinical trials conducted outside the EU / EEA that are linked to European paediatric-medicine development.' - homepage
- The Cochrane Central Register of Controlled Trials (CENTRAL)Primarily includes reports of randomised trials sourced from MEDLINE and Embase. Records from other sources such as trials registers and conference proceedings may also be present. CENTRAL includes the contents of the CRG Specialized Registers, collections of controlled trials relevant to each Review Group's area of interest and maintained by Cochrane Information Specialists
- ISRCTN registry (part of BioMed Central)A registry of curated records for clinical studies from around the world, the ISRCTN registry makes registration data publicly available in a standard form meeting requirements set out by the World Health Organisation and the International Committee of Medical Journal Editors. The majority of studies are undertaken by sponsors based in the United Kingdom
- CenterWatchOffers services targeted to clinical research professionals and prospective trial participants worldwide, including the iConnect database of clinical trials. Also provides profiles of research centres and industry providers offering a variety of services related to conduct of clinical trials.
- National Cancer Institute (USA) - Clinical Trials Information for Patients and CaregiversIncludes information about NCI-supported clinical trials underway in the United States, Canada and internationally
- Canadian Cancer TrialsA service of the Canadian Partnership Against Cancer, this site includes details of trials underway across Canada. Data meets requirements set out by the World Health Organisation and the International Committee of Medical Journal Editors
- Cancer Research UK - Find a clinical trialThis clinical trials database aims to list all cancer trials and studies recruiting in the United Kingdom
Guidelines and standards
- Cochrane Handbook, part 2, chapter 4.3.3: Trials registers and trial results registers
This section provides details on searching for current and past clinical trials.
'If study registers (such as ClinicalTrials.gov)...were searched, specify the name of each source and any date restrictions that were applied.' - PRISMA 2020 Explanation and Elaboration, p. 5
- Searching clinical trials registers: guide for systematic reviewersHunter et al. (2022). BMJ, 377, e068791. https://doi.org/10.1136/bmj-2021-068791
'...provides 11 steps and several key recommendations on where to search, how to formulate search strategies, efficient screening methods, and reporting searches'
How to search trial registers
A great resource that details which search methods are possible within various trials registers. If you've ever wondered if ClinicalTrials.gov allows for nesting or truncation, this site is for you.
- Finding clinical trials, research registers and research resultsContains links to registers and guides on how to search the registers (website managed by Julie Glanville and Carol Lefebvre).