A systematic review is a type of article that uses a systematic and comprehensive review of the literature to answer a single research question. Systematic reviews are common in health fields and are often written to guide practice in cases where there is an abundance of literature, particularly if not all the literature is in agreement.
|Answers a highly specific (usually clinical) question||Summarizes a topic that may be either broad or narrow|
Uses a pre-determined systematic, comprehensive and replicable search strategy.
Often includes searches of grey literature sources to reduce the risk of publication bias affecting the results.
|Searching may be done organically and in a non-prescribed manner.|
|Studies are selected based on a number of clear, pre-determined criteria, including relevance, study type, year or publication, and quality.||No justification for the inclusion of a study or article is required.|
Selection and inclusion criteria
Systematic search strategy
Appraisal of existing research
Synthesis of findings
Role of Librarians in Systematic Reviews
Most books and guidelines on writing systematic reviews recommend the participation of a librarian at the searching stage. This is because the style and depth of searching used in systematic review requires specific training and a thorough understanding of the systematic approach. At UNB Libraries, there are currently two librarians who provide systematic review support (Richelle Witherspoon and Alex Goudreau) and we provide two levels of support in our roles: consultation and systematic & scoping review service.
When acting as a consultant for a systematic review, the librarian:
- Will provide consultation on how to conduct a comprehensive search strategy
- Will suggest how to organize research and keep detailed records of search results and strategies
- Will not be a member of the team nor create the search strategies
- Will train team members on the use of citation management tools
- Will train team members on the use of database platforms
- Will advise on database selection
- Will train team members on obtaining full-text of articles
Systematic Review & Scoping Service
When performing systematic review and scoping services, the librarian:
- Will create, validate, and translate search strategies
- Will export search results to a citation management tool
- Will document search strategies
- Will be part of the team
- Will be included as a coauthor on publication(s)
Note 1: Librarian availability to assist with systematic reviews may vary based on the time of year and the number of reviews being requested. Please be aware that your request may be deferred, and/or you may be referred to another librarian.
Note 2: In general, when the systematic review is being completed as coursework or for a thesis / dissertation, librarians will act only as consultants.
Finding Existing Systematic Reviews
Before starting a new systematic review you must show that there is not already an existing systematic review - or systematic review protocol - on your topic. If there is an existing review, you must be able to justify the need for a new one based on the age of the review, the applicability to your question, and/or the manner in which the previous review was performed.
Check Subject Databases
Do a thorough search of any databases that you consider relevant to your topic. In addition to using keywords to bring up the topic you are interested in, include search terms like "systematic review", "scoping review", "umbrella review", and "meta analysis" to narrow your search down to the article types you are interested in.
Check Systematic Review Providers & Registries
The Cochrane Collaboration is a group that solicits and creates systematic reviews on clinical topics. Their database contains a wide range of resources, but is most well-known for its extensive collection of systematic reviews.
- Cochrane Library The Cochrane Library contains high-quality, independent evidence to inform healthcare decision-making. This database includes the Cochrane Database of Systematic Reviews, the Database of Abstracts of Reviews of Effects, the Cochrane Central Register of Controlled Trials, the Cochrane Database of Methodology Reviews, the The Cochrane Methodology Register, the Health Technology Assessment Database, and the NHS Economic Evaluation Database.
Access to the Cochrane Library in New Brunswick is through a province-wide license made possible by a partnership between UNB and the eight Regional Hospital Authority libraries.
Unlimited simultaneous users.
PROSPERO is a systematic review registry. This means that it is a place where researchers signal their intent to write a systematic review on a given topic. Searching PROSPERO lets you know whether a review on your topic is already in progress and might be completed before yours.
It is also a good idea to register your own review in PROSPERO.
Joanna Briggs Institute
The Joanna Briggs Institute (JBI) is another solicitor / creator of systematic review that focuses specifically on nursing and allied health related topics. To find out if there are any JBI reviews completed or pending on your topic, you must go to two different places:
- JBI's Registered Titles to find out if there is a systematic review that is currently in progress
- CINAHL or PubMed to find out if there is a completed systematic review on your topic
Since it is likely that you have already searched CINAHL or PubMed for systematic reviews when checking your subject specific databases, you probably don't need to do a special search for this. However, if you have a specific need to know if there is a JBI review on a topic, you can do your regular keyword search and then append the following to your search:
CINAHL: JN("JBI database of systematic reviews & implementation reports" OR "JBI library of systematic reviews")
PubMed: ("JBI database system rev implement rep" OR "JBI Libr Syst Rev" OR "JBI Evid Synth")
Appending the above phrase to your search will direct the database to only bring forward JBI reviews and will exclude all other database content.
Components of Systematic Reviews
While the contents of a systematic review vary based on the type of systematic review being done (see SR Types), most good systematic reviews do share a number of core components:
A brief background on the topic that describes its context and importance
The specific question to be addressed by the systematic review. The question often follows the PICO format, but as long as it is both clear and sufficiently detailed, this is not strictly necessary.
The inclusion criteria (which can also be framed as exclusion criteria in some SRs) are the guidelines that reviewers follow when determining whether a specific item will be considered in the systematic review. These criteria are often rigidly adhered to and constitute a promise to the readers by the reviewers that only the items that fit all the criteria were included in the review.
The participants section includes a description of the population(s) of interest in the review.
Phenomenon / Exposure / Intervention
The phenomenon / exposure / intervention usually describes the main issue of interest in the systematic review.
Types of Studies
The types of studies section typically lists the types of research that were considered for inclusion. The specific contents of this section vary widely between the types of systematic reviews and even within types as it is influenced by the amount of research available and by the types of research that have been performed. Additionally, this is the one section where the criteria may be a little more flexible, as it may include a statement like "other types of studies were considered for inclusion if they were deemed to be highly relevant and of good quality."
The methods section includes a detailed description of how the systematic review was carried out. Because systematic reviews are done based on a prescribed set of rules and criteria, most methods sections contain the same types of information.
The search strategy section describes how the search how search terms were generated and how the search protocol was developed, what databases were used, the date that the search was performed, and whether any grey literature sources were searched.
Note that while the search strategy / protocol is often very complex and reflects a similar approach when it is being used in traditional article databases, grey literature searching in systematic reviews does not follow the same criteria. Few grey literature sources are large or sophisticated enough to make the use of advanced searching strategies practical, but are often included in the search strategy as a way to mitigate the effects of publication bias.
The study selection section describes the process by which the two (or more) reviewers selected items for inclusion in the review. It includes such information as the number of reviewers, the appraisal ratings that were considered acceptable and how they were obtained, and how differences of assessment were resolved between reviewers.
The data extraction section (which can go by other names) describes how information from each included article / item was recorded and used. In the case of quantitative SRs, for example, specific information is usually extracted and recorded in table to make comparisons between studies (then arranged in rows) easier.
The results section describes the outcomes of each of the processes implemented in the methods. It provides information about the number of studies included, the appraisals of the studies, and a brief description of the studies.
Study inclusion (and PRISMA diagram)
The study inclusion section details the number of studies that were retrieved, the number of duplicates removed, the number that were considered relevant, the number that passed the appraisal criteria and the total number of studies that were finally considered for review. This information is almost always provided in the form of a short paragraph, and is sometimes also provided in the form of a PRISMA Flow Diagram. There may also be a summary of the most common reasons that articles were excluded from the review.
The methodological quality section provides a summary of the overall appraised quality of the included articles. This typically includes a brief paragraph and a more detailed table that summarizes the appraisals for each article.
Characteristics of included studies
This section provides a quick overview of the specific details of the studies that were included, such as study type, number of participants, and geographical location. It does not typically include mention of the outcomes of the studies.
This section describes the overall findings of the systematic review.
This section discusses the review findings in the context of the literature and in practice.
Appendix - Search strategy or strategies
This section contains a copy of the exact search that was performed in at least one of the databases (some reviews include copies of all the searches performed). It does not include results of those searches, but instead provides insight into the keywords, subject terms, proximity searches, Boolean operators, etc. that were used to retrieve the items for review.
Types of Systematic Reviews
There are many types of systematic reviews, and each differs slightly in its approach to the literature and its ultimate goal.
Below is a list of the most common types of systematic reviews, and JBI has a great series of videos explaining more about the different types.
SR of qualitative evidence
A review of the qualitative evidence on a topic. SRs of qualitative evidence involve analyzing the findings and themes of multiple qualitative studies on a topic (of various types and approaches) and using the extracted information to obtain a wholistic perspective on the phenomenon.
SR of quantitative evidence
A review of the quantitative evidence on a topic. SRs of quantitative evidence focus on using studies (like RCTs) to determine whether an intervention is effective and/or the degree of effectiveness of the intervention.
SR of text and opinions
A review of texts and opinions that is performed only when higher quality evidence is not available. In the absence of qualitative and quantitative studies, this type of SR reviews expert opinions, consensus, and comments from the literature to suggest an answer.
SR of prevalence and incidence
A review of studies and data describing the prevalence or incidence of an issue. SRs of prevalence and incidence describe the geographic, demographic, physiological and social variations pertaining to a particular issue to help inform health practices and resource allocation.
SR of economic evidence
A review of the research describing the economic impact of a specific health issue or type of care. SRs of economic evidence review and synthesize literature to evaluate the cost-benefit of a health issue and a care program related to it.
SR of etiology and risk
A review of studies and data describing the risk factors associated with a particular issue. SRs of etiology and risk describe the factors that increase or decrease the risk of an issue and can be used to inform health policy and resource allocation.
Mixed Methods SR
A review that includes both qualitative and quantitative methods. Mixed methods SRs provide a combination of effectiveness and experiential information on a topic that results in a powerfully wholistic review.
Diagnostic Test Accuracy SR
A review that analyzes the results of studies that test the accuracy of a specific diagnostic test. Diagnostic test accuracy SRs take the results of all available studies on the accuracy of a test and use them to determine that test's overall accuracy as well as any factors that affect / alter it.
A reviews that assesses the existing systematic reviews (or clinical guidelines) on a topic when there is more than one available. Umbrella reviews evaluate the thoroughness and quality of the procedures implemented in the systematic reviews they consider and synthesize the findings to arrive at a single conclusion.
A review that addresses the literature on a topic in its entirety. Scoping reviews tend to consider slightly broader questions than other SRs and assess all the literature available on a topic; they tend to be performed on topics that are emerging or not heavily researched.
Sample Systematic Reviews
Mohseni, M., Azami-Aghdash, S., Sheyklo, S. G., Moosavi, A., Nakhaee, M., Pournaghi-Azar, F., & Rezapour, A.
International Journal of Community Based Nursing & Midwifery
Husk K., Lovell R., Cooper C., Stahl‐Timmins W., & Garside R.
Cochrane Database of Systematic Reviews
Gomes, L., Horta, K., Gonçalves, J., & Santos-Pinto, A.
European Journal of Orthodontics
Nabavi, F. H., Vanaki, Z., & Mohammadi, E.
Western Journal of Nursing Research
Lapkin, S., Levett-Jones, T., Bellchambers, H., & Fernandez, R.
Clinical Simulation in Nursing
Systematic Searching Video Series
This section includes links to a video series that walks you through the process of developing a systematic search step by step. These videos focus solely on the search development and execution portion of the knowledge synthesis process. Videos should be watched in order, and each video has a task that should be completed before the next video is watched.
*** It may be worthwhile to watch video 16 early in your searching process, as it offers tips that will be useful throughout. ***
SR Bootcamp Videos
This section includes links to videos about how to complete a systematic review. These videos are recordings from the spring / summer of 2019 "Systematic Reviews Bootcamp" that was offered by UNB Libraries and cover the entire process of performing a systematic review.