An effective systematic review "collates all empirical evidence that fits pre-specified eligibility criteria in order to answer a specific research question" (Cochrane Handbook for Systematic Reviews of Interventions) .
The Centre for Reviews and Dissemination at York estimates that a team will take 9-24 months to complete a systematic review. Systematic reviews can be of interventions (i.e. randomised controlled trials) or observations (i.e. case control or cohort studies).
A systematic review should have:
“the quality of a systematic review depends on the quality of the studies appraised. It can be difficult to reach meaningful conclusions from reviews of low-level evidence, and thus, systematic reviews are commonly limited to high-level evidence (Level I or II) studies (RCTs)”.
Wright, R.W., Brand, R.A., Dunn,W. & Spindler, K.P. (2007). How to Write a Systematic Review.
Why are systematic reviews necessary?
Problems with systematic reviews
( Introduction to systematic reviews by Susan Shenkin)
Systematic Reviewlution is a living review of systematic reviews! Here you will see evidence of where systematic reviews are not being done well. Awareness of the problems will enable researchers to conduct better systematic reviews in future.
|
Criteria |
Systematic Reviews |
Literature Reviews |
| Question |
Focused on a single question (often PICO based) |
Not necessarily focused on a single question - may describe an overview |
| Protocol |
A peer reviewed protocol or plan is included |
No protocol included |
| Background |
Summarises the available literature |
Summarises the available literature |
| Objectives |
Clear objectives are identified |
Objectives may or may not be identified |
| Inclusion/Exclusion Criteria |
Criteria stated before the review is conducted |
Criteria not stated |
| Search Strategy |
Comprehensive and systematic (stated in the document) |
Strategy not explicitly stated (not always comprehensive or systematic) |
| Process of Selecting Articles |
Usually clear and explicit |
Not described in a literature review |
| Process of Evaluating Articles |
Comprehensive evaluation of study quality |
Evaluation of study quality may or may not be included |
| Process of Extracting Information |
Usually clear and specific |
Not clear or explicit |
| Results & Data Synthesis |
Clear summaries of studies based on high quality evidence |
Summary based on studies where the quality of the articles may not be specified. May also be influenced by the reviewer's theories, needs and beliefs. |
| Discussion |
Written by an expert or group of experts with a detailed and well grounded knowledge of the issues |
Written by an expert or group of experts with a detailed and well grounded knowledge of the issues |
(from Curtin University Library's Systematic Review guide)