Clinical trials and systematic reviews
These websites provide information about or enable you to search for clinical trials:
- Current Controlled Trials (including ISRCTN.org, mRCT, UK Clinical Trials Gateway) (multinational)
- ClinicalTrials.gov (multinational)
- WHO International Clinical Trials Registry Platform (ICTRP)
ICTRP links to trials registers from Australia & New Zealand, China, Germany, India, Iran, Japan, Netherlands, Sri Lanka and ISRCTN.org
- Trials Central (USA)
- EMEA - European Medicines Agency
- CenterWatch (mainly USA)
- National Cancer Institute (multinational)
- IAVI Database of AIDS Vaccine Candidates in Human Trials
- NIHR Clinical Research Network Portfolio (UK)
Pharmaceutical company registers:
- Eli Lilly and Company Clinical Trial Registry
- Pfizer Clinical Trials
- GlaxoSmithKline Clinical Study Register
- PROSPERO register
This enables you to search for prospectively registered systematic reviews in health and social care
- Cochrane Library
This contains a suite of databases which enable you to search for systematic reviews and clinical trials. The databases inside this resource which will be of particular interest are Cochrane Reviews, Other Reviews and Clinical Trials. What you can expect to find in each of the databases inside the Cochrane Library.
Use this workbook Cochrane Library workbook (PDF) to search the database(s) in more detail
If you have been searching for references in other databases like Medline, you may be able to limit your results to only those that are systematic reviews or clinical trials. See the section on using search filters.
The Centre for Reviews and Dissemination (CRD) offers the following useful definitions*:
A clinical trial with a control group.
The group that acts as a comparator for one or more experimental interventions in a controlled trial. The group without the disease or outcome of interest in a case control study.
Randomised controlled trial
An experiment in which investigators use randomisation to allocate participants into the groups that are being compared. Usually allocation is made at individual level, but sometimes it is done at group level, eg by schools or clinics.
Systematic reviews aim to identify, evaluate and summarise the findings of all relevant individual studies, making the available evidence more accessible to decision-makers. When appropriate, combining the results of several studies gives a more reliable and precise estimate of an intervention's effectiveness than one study alone.
Systematic reviews adhere to a strict scientific design based on explicit, pre-specified and reproducible methods. Because of this, when carried out well, they provide reliable estimates about the effects of interventions so that conclusions are defensible. As well as setting out what we know about a particular intervention, systematic reviews can also demonstrate where knowledge is lacking. This can then be used to guide future research.
*CRD. 2008. Systematic reviews : CRD's guidance for undertaking reviews in health care. York: CRD, University of York