Systematic Reviews
Where to search
In conducting a systematic review, it is important that you search widely through published and unpublished research, to find all information available on a particular topic.This usually includes searching sources such as:
- Bibliographic databases
- Trials registers
- Reviews and guidelines
- Grey literature
- Hand searching other relevant sources.
Databases
The databases you choose to search will depend on the topic of your systematic review. It is important to search a range of multidisciplinary and subject specific databases.
You can access a wide variety of databases via the Database A-Z linked from the Primo homepage.
There are guides and tutorials on how to use each database here.
You can create personal accounts on most database provider website which will allow you to save searches, mark papers to return to and to set up alerts when new items are added to the database on your research topic.
Trials Registers
Why are the results of trials important to consider?
It is important that all healthcare decisions are informed by all available evidence, thus overcoming publication bias and selective reporting. The data contained in clinical trials that are unpublished or ongoing, can provide important additional clinical evidence.
Development of trial registers
In the past decade mandates around registration of trials has increased their retrievability in trial registers. There is increasing acceptance on behalf of investigators of the importance of registering trials at inception and unwillingness of leading medical journal publishers to publish reports of trials not properly registered. Cochrane Handbook (Part 2, section 6.2.3).
No single resource gives access to all trials, and multiple registers should be searched as broadly as possible. Examples include:
- PROSPERO - Contains over 2000 records of prospectively registered systematic reviews, valuable resource for identifying on-going reviews to help avoid unplanned duplication of reviews.
- WHO International Clinical Trials Registry Platform (ICTRP) - key trials register portal
- Cochrane Central Register of Controlled trials (CENTRAL) - incudes trials published in bibliographic databases such as Medline and Embase, as well as those from other published and unpublished sources
- Clinicaltrials.gov (a service of the U.S. National Institutes of Health)
- ISRCTN Registry - first online service that provided unique numbers to randomized controlled trials in all areas of health care and from all countries around the world.
Further discussion on this topic can be found in the article below:
Grey Literature
It will depend on the purpose and scope of the review whether or not to include grey literature in your search, however, there are a number of reasons why it may be important to include in your review:
- Grey literature can provide further sources of evidence for your review
- It can provide a more rounded view of your field of research with access to different perspectives
- It can help balance publication bias e.g. often negative and neutral research results are not published by conventional means
- It can be a source of raw data
- It can provide more currency to your review through access to the most up-to-date and pre-publication material
For more information see the Using grey literature guide.
Hand Searching
"Handsearching involves a manual page-by-page examination of the entire contents of a journal issue or conference proceedings to identify all eligible reports of trials. In journals, reports of trials may appear in articles, abstracts, news columns, editorial, letters or other text" (Cochrane Handbook, 6.2.2.1)
Why is handsearching important?
For the trials that are reported, they may not be easily identified as trials due to indexing issues associated with some databases
Note: Conference proceedings are important to hand search because individual conference papers are rarely indexed.
For more information, refer to: