Systematic Reviews and Evidence Based Practice: Systematic review

• Systematic Reviews address a specific clinical question, following an explicit and rigorous methodology.
• They evaluate and summarise findings of all relevant individual studies, and if appropriate, combine the results of several quantitative studies to provide more reliable results (meta-synthesis/meta-analysis). Searching is exhaustive and continuous over a period of 12-18 months.

• Meta-analysis is the use of statistical methods to summarise the results of independent studies- Meta-analyses will always be accompanied by a systematic review, but a systematic review may not always have a meta-analysis. Meta-analyses aims for exhaustive searching. May use funnel plot to assess completeness.

• Systematic Reviews are considered the ‘gold standard’ of reviews because the review is based on explicit, prespecified and reproducible methods used to systematically search all sources of evidence and critically appraise, summarise and synthesise research findings to address a highly focused clinical question.

• They use explicit criteria to include / exclude studies and apply established standards to critically appraise study quality.

• Due to its formal nature, it occupies prime importance in evidence-based health care information, using explicit methods to deal with research questions in order to identify reliable and quality data on a particular topic, thus reducing chances for bias. This type of review is sometimes considered an original article, replicable by any other researcher due to its demanding protocol.

• Not all topics have sufficient research evidence to allow a meta-analysis to be conducted.  In that case, an integrative review is an appropriate strategy.

A systematic literature review is a type of research technique designed to answer a focused research question . It is conducted in an unbiased, reproducible and reliable way to provide evidence for practice and policy-making and to identify gaps in research. Authors should conduct a methodical and comprehensive literature synthesis focused on a well-formulated research question, usually that fits a PICO template. Its aim is to identify and synthesize all of the research on a particular topic. Every step of the review, including the search, must be documented for reproducibility. 

Should you do a systematic Review?

• Is there enough literature on the topic to justify a review? Systematic reviews are designed to extract the evidence from many studies to provide an analytical understanding of an intervention etc.. Is there a body of evidence available to analyze, or does more primary research need to be done?
• Do you have a clearly defined clinical question with established inclusion and exclusion criteria? Systematic review questions should be specific and clearly defined. Questions that fit the PICO (problem/patient, intervention, comparison, outcome) format are usually well-suited for the systematic review methodology
• Do you have the statistical resources to analyze and pool data? What type of data is required?
• Do you have the time to commit to properly conduct a systematic review?
• If your project does not meet the above criteria, there are many more options for conducting a synthesis of the literature.

Ulster University staff and students can access Cochrane Interactive Learning. A series of eleven online learning modules covering areas such as, searching, selecting, analysing and writing systematic reviews.

Module 1 of the Cochrane Interactive Learning resource provides an introduction to conducting a systematic review and details the PICO.

What's in a name? The difference between a Systematic Review and a Literature Review, and why it matters

by Lynn Kysh, MLIS, University of Southern California - Norris Medical Library