A literature review is a study which:
There are many types of literature review, but two of the main ones are:
GRADE (Grading of Recommendations, Assessment, Development, and Evaluations) is a transparent framework for developing and presenting summaries of evidence and provides a systematic approach for making clinical practice recommendations.
GRADE assessments of certainty are determined through consideration of five domains:
risk of bias,
inconsistency,
indirectness,
imprecision and
publication bias.
Also called a literature review.
A narrative, or literature, review synthesises primary studies and explores this through description rather than statistics.
A scoping review is a preliminary assessment of the potential size and scope of available research literature. Aims to identify the nature and extent of research evidence (usually including ongoing research).
Scoping reviews provide an understanding of the size and scope of the available literature and can inform whether a full systematic review should be undertaken.
If you're not sure you should conduct a systematic review or a scoping review, this article outlines the differences between these review types and could help your decision making.
Rapid reviews are an assessment of what is already known about a policy or practice issue by using systematic review methods to search and critically appraise existing research.
This methodology utilises several legitimate techniques to shorten the process – careful focus of the research question, using broad or less sophisticated search strategies, conducting a review of reviews, restricting the amount of grey literature, extracting only key variables and performing more simple quality appraisals.
Rapid reviews have an increased risk of potential bias due to their short timeframe. Documenting the methodology and highlighting its limitations is one way to mitigate bias.
A meta-analysis statistically combines the results of quantitative studies to provide a more precise effect on the results. This type of study examines data from multiple studies, on the same subject, to determine trends.
Outcomes from a meta-analysis may include a more precise estimate of the effect of treatment or risk factor for disease, or other outcomes, than any individual study contributing to the combined studies being analysed.
Refers to any combination of methods where one significant component is a literature review (usually systematic review). For example, a mixed methods study might include a systematic review accompanied by interviews or by a stakeholder consultation.
Within a review context, mixed methods studies refers to a combination of review approaches. For example, combining quantitative with qualitative research or outcome with process studies.
Systematic reviews are considered the most reliable evidence sources for several reasons:
Comprehensive and rigorous methodology: Systematic reviews follow a structured and rigorous methodology to identify, select, appraise, and synthesize relevant studies on a specific topic. This systematic approach helps minimize bias and increases the reliability of the findings.
Inclusion of multiple studies: Systematic reviews aim to include all relevant studies available on a specific topic, rather than relying on a single study. By pooling data from multiple studies, systematic reviews can provide a more comprehensive and robust analysis of the evidence.
Transparent and reproducible process: Systematic reviews provide detailed information about their methodology, including search strategies, inclusion and exclusion criteria, and data analysis methods. This transparency allows other researchers to replicate the review process and verify the results, enhancing the credibility and reliability of the findings.
Minimization of bias: Systematic reviews employ specific strategies to minimize bias. These include a comprehensive search for relevant studies, the use of predefined inclusion criteria, assessment of study quality, and statistical methods to combine and analyze data. By minimizing bias, systematic reviews provide a more objective and accurate summary of the available evidence.
Statistical power and precision: By pooling data from multiple studies, systematic reviews increase the statistical power and precision of the findings. This allows for more robust conclusions and generalizability of the results.
Assessment of study quality: Systematic reviews often include an assessment of the quality and risk of bias in individual studies. This evaluation helps identify limitations and potential sources of bias, allowing reviewers to provide a more nuanced interpretation of the evidence.
Updateability: Systematic reviews are periodically updated to incorporate new evidence as it becomes available. This ensures that the review remains current and reflects the most up-to-date knowledge on a particular topic.
While systematic reviews are generally considered a reliable source of evidence, it is still important to critically evaluate the quality and relevance of each review to ensure its applicability to a specific context or question.