A systematic review aims to provide a comprehensive, unbiased synthesis of many relevant studies into a single document using rigorous and transparent methods. A systematic review aims to synthesize and summarize existing knowledge in order to inform policy and practice.
Type of Reviews
A literature review, or narrative review, is an attempt to obtain and synthesise the results and conclusions of key publications on a given topic. Literature reviews often do not answer one specific question like a systematic review does, and they usually bring together a summary of the literature in a qualitative manner. They may be a first step in determining the current state of the literature on a topic.
A literature review may be undertaken in a systematic way in order to be comprehensive, without being a systematic review. It is important to recognise the differences between the two and determine which type of review is best suited to your needs - or whether one of the other reviews detailed here is more applicable.
Scoping reviews are exploratory in nature and are used to systematically search the literature and map the key concepts underpinning a research area as well as to clarify working definitions, and/or the conceptual boundaries of a topic. Scoping reviews may be undertaken as a preliminary exercise prior to the conduct of a systematic review, or as a stand alone review.
Scoping reviews may:
Adapted from: Peters MDJ, Marnie C, Tricco AC, Pollock D, Munn Z, Alexander L, McInerney P, Godfrey CM, Khalil H. Updated methodological guidance for the conduct of scoping reviews. JBI Evidence Synthesis. 2020;18(10):2119-2126. doi:10.11124/jbies-20-0016
Further reading and guidance:
Peters MDJ, Godfrey C, McInerney P, Munn Z, Tricco AC, Khalil, H. Chapter 11: Scoping Reviews (2020 version). In: Aromataris E, Munn Z (Editors). JBI Manual for Evidence Synthesis, JBI, 2020. Available from https://synthesismanual.jbi.global.
Munn Z, Peters MDJ, Stern C, Tufanaru C, McArthur A, Aromataris E. Systematic review or scoping review? Guidance for authors when choosing between a systematic or scoping review approach. BMC Med Res Methodol. 2018;18:143.
Rapid reviews are a form of accelerated systematic review. They are usually undertaken when decision makers have urgent and emerging needs which require evidence produced on a short time frame. Typically, to compensate for the short time frame of a rapid review, methodological rigour may be sacrificed. Cochrane defines rapid reviews as "a form of knowledge synthesis that accelerates the process of conducting a traditional systematic review through streamlining or omitting specific methods to produce evidence for stakeholders in a resource-efficient manner.”
Garritty C, Gartlehner G, Kamel C, King VJ, Nussbaumer-Streit B, Stevens A, Hamel C, Affengruber L. Cochrane Rapid Reviews. Interim Guidance from the Cochrane Rapid Reviews Methods Group. March 2020.
Hamel C, Michaud A, Thuku M, Skidmore B, Stevens A, et al. Defining rapid reviews: a systematic scoping review and thematic analysis of definitions and defining characteristics of rapid reviews. J Clin Epi. 2021;129:74-85. doi: 10.1016/j.jclinepi.2020.09.041
Umbrella reviews are sometimes referred to as a "review of reviews". They are an attempt to identify and appraise, extract and summarise all the evidence from research syntheses related to a topic or question.
Umbrella reviews may:
Umbrella reviews offer the possibility to address a broad scope of issues related to the topic of interest.
Adapted from: Aromataris E, Fernandez R, Godfrey C, Holly C, Khalil H, Tungpunkom P. Chapter 10: Umbrella Reviews. In: Aromataris E, Munn Z (Editors). JBI Manual for Evidence Synthesis. JBI, 2020. Available from https://synthesismanual.jbi.global. https://doi.org/10.46658/JBIMES-20-11
There are many mnemonics available to assist you to formulate a search strategy based on the type of review you are undertaking and the kind of question you are asking. You may like to consider some of techniques below to help you with this process.
|PICO(S)||Population - Intervention - Comparator - Outcome - (Study design)||Reviews of effectiveness|
|PICo||Population - Phenomena of Interest - Context||Qualitative reviews
Expert opinion / Policy
|PEO||Population - Exposure - Outcome||Aetiology and Risk|
|CoCoPop||Condition - Context - Population||Prevalence and Incidence|
|PIRD||Population - Index test - Reference test - Diagnosis of interest||Diagnostic test accuracy|
|PCC||Population - Concept - Context||Scoping reviews|
|PICOC||Population - Intervention - Comparator(s) - Outcome - Context||Costs / Economic evaluation|
|CPIMP||Construct of interest - Population - Type of measurement instrument - Measurement properties||Psychometric|
|PFO||Population - Prognostic Factors - Outcome||Prognostic|
|SPIDER||Sample - Phenomenon of Interest - Design - Evaluation - Research type||Qualitative and mixed methods|
|SPICE||Setting (where?) - Perspective (for whom?) - Intervention (what?) - Comparison (Compared with what? - Evaluation (with what result?)||Qualitative|
|ECLIPSE||Expectation (improvement or information or innovation) - Client group (at whom the service is aimed?) - Location (where is the service located?) - Impact (outcomes) - Professionals (who is involved in providing/improving service?) - Service (for which service are you looking for information?)||Health policy/ Management information|
Use the above mnemonics to construct your research question and break down your search strategy. Remember that equal emphasis may not be put on each part of the mnemonic, and will largely depend on the topic of your systematic review.
|Population||How would I describe a patient/problem/situation similar to mine?|
|Intervention||Which main intervention am I considering?|
|Comparison||What is the main alternative?|
|Outcome||What could this intervention accomplish, measure, improve or affect?|
|Study design||Which study design will best answer my question?|
Have you checked to see if there is an existing systematic review answering your research question? This will help avoid duplication and it will help you construct your search strategy by identifying what search terms and databases were used.
To locate existing systematic reviews you can try:
Your protocol will describe the rationale, hypothesis, and planned methods of the systematic review. It should be prepared before you start and be used as a guide through out the review.
For more information go to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) website.
For guidance on the reporting of Literature Searches in Systematic Reviews go to the PRISMA-S
It is highly recommended that you register or publish your systematic review protocol prior to undertaking the review. This:
For systematic reviews, umbrella reviews and rapid reviews related to health sciences, PROSPERO is a highly respected international review register. For Environmental and Agricultural sciences see the Collaboration for Environmental Evidence.
Please note : PROSPERO does not accept scoping reviews nor has the resources to register reviews done as part of training courses. Other places to register protocols include: