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Scoping Review
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Systematic Review
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Evidence Synthesis
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Meta-Analysis
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Realist Review
Rapid Review
Systematic Review
Systematic Reviews (SRs) focus on systematically summarising evidence on a specific question, typically through quantitative means, and aim to provide a clear, objective answer based on the best available evidence. They are necessary when there are no existing SRs and the evidence base is either overwhelming, contradictory or both.
Check Cochrane https://www.cochranelibrary.com/ and PROSPERO https://www.crd.york.ac.uk/PROSPERO/ databases for any existing and proposed SRs respectively. It is a requirement of NIHR funding that proposed systematic reviews are pre-registered in the PROSPERO database.
Purpose:
- To Synthesise Evidence: The primary aim is to systematically collect, evaluate, and synthesise research evidence on a specific research question or topic.
- To Provide Comprehensive Answers: To offer a comprehensive and objective summary of the existing evidence, often to inform practice, policy, or further research.
Characteristics:
- Structured Methodology: Follows a predefined, rigorous methodology, including a systematic search strategy, inclusion and exclusion criteria, and standardised data extraction procedures.
- Comprehensive Search: Involves a thorough search of multiple databases and sources to identify all relevant studies, minimising the risk of missing important evidence.
- Quality Assessment: Includes an assessment of the quality and risk of bias of included studies, often using standardised tools.
- Data Synthesis: May include statistical techniques like meta-analysis to combine quantitative data from different studies to produce pooled estimates of effect.
- Transparency and Reproducibility: The process is transparent, with detailed reporting of methods and findings to ensure reproducibility. Adheres to guidelines such as PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses).
- Focus: Typically focused on answering specific clinical or research questions with quantitative data, though qualitative data can also be included.
Timescale:
- 6 to 12 months: Systematic reviews usually take between 6 to 12 months to complete, although the duration can extend depending on the complexity of the topic, the volume of literature, and the resources available. The Cochrane guidance suggests that literature searching be only as comprehensive as time and resources allow.
Qualitative Systematic Review (Qualitative Evidence Synthesis)
Qualitative systematic reviews have similar aims to the quantitative systematic review but additionally has the following purpose and characteristics
Purpose:
- To synthesise qualitative research to provide insights into phenomena, experiences, processes, attitudes or beliefs.
- To develop or refine theories by identifying patterns, themes, and relationships within the qualitative evidence
- To inform practice, policy-making, and further research by providing a nuanced understanding of how and why certain outcomes occur.
Characteristics:
- Involves extracting qualitative data (e.g., themes, concepts) and synthesising it through methods like thematic synthesis, meta-ethnography, or narrative synthesis.
- Focus on subjective experiences, emphasising understanding the meanings, perspectives and experiences of participants as reported in the original qualitative studies.
- Includes a rigorous appraisal of the quality and credibility of the included studies, often using specific criteria tailored to qualitative research.
- Pays close attention to the context in which the original studies were conducted, ensuring that the synthesis reflects the diversity and richness of the qualitative data.