What is a Systematic Review?
A systematic review attempts to identify, appraise and synthesize all the empirical evidence that meets pre-specified eligibility criteria to answer a given research question. Researchers conducting systematic reviews use explicit methods aimed at minimizing bias, in order to produce more reliable findings that can be used to inform decision making.
What is a Meta-Analysis?
If the results of the individual studies are combined to produce an overall statistic, this is usually called a meta-analysis. Many Cochrane Reviews measure benefits and harms by collecting data from more than one trial, and combining them to generate an average result. This aims to provide a more precise estimate of the effects of an intervention and to reduce uncertainty.
Definitions provided by About Cochrane Reviews.
Characteristics of reviews to consider:
|Question||Broad in scope||Exploratory||Well-defined and focused||Well-defined and focused||Well-defined and focused|
|Search||Not specified; potentially biased||Completeness of searching determined by time constraints||Completeness of searching determined by time constraints||May or may not be included in publication||Exhaustive, comprehensive, and reproducible|
|Appraisal||None||None||Time-limited assessment||May or may not include||Yes, important part of review|
|Synthesis||Narrative||Typically tabular with some narrative||Typically narrative and tabular||Typically narrative with tabular accompaniment||Typically narrative and tabular|
|Team||No||Yes||Yes||May or may not have a team||Yes|
|Meta-analysis of results||No||No||No||No||Sometimes|
|Time||<3 months||4-12 months||<4 months||8-12 months||12-18 months|
Adapted from Grant, M. J., & Booth, A. (2009). A typology of reviews: an analysis of 14 review types and associated methodologies. Health Information & Libraries Journal, 26(2), 91-108.
Timeline for a Cochrane Review
1 - 2 Preparation of protocol
3 - 8 Searches for published & unpublished studies
2 - 3 Pilot test of eligibility criteria
3 - 8 Inclusion assessments
3 Pilot test of 'Risk of Bias' assessment
3 - 10 Validity assessments
3 Pilot test of data collection
3 - 10 Data collection
3 - 10 Data entry
5 - 11 Follow up of missing information
8 - 10 Analysis
1 - 11 Preparation of review report
12 - Keeping the review up to date