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Systematic Review

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"A systematic review attempts to identify, appraise and synthesize all the empirical evidence that meets pre-specified eligibility criteria to answer a specific research question. Researchers conducting systematic reviews use explicit, systematic methods that are selected with a view aimed at minimizing bias, to produce more reliable findings to inform decision making".

In contrast to the traditional literature review, systematic literature reviews use a more rigorous and precise approach to reviewing the literature in a specific subject area.

Why are systematic reviews important?

  • They deliver a clear and comprehensive overview of available evidence on a given area.
  • They help identify research gaps in our current understanding of a field.
  • They can highlight methodological concerns in research that can be used to improve future work in the area.
  • They can be used to identify questions for which the available evidence provides clear answers and consequently further research is not needed.

What's included in Systematic Reviews:

  1. Address one specific issue
  2. Have a specific goal or objective
  3. Define the criteria for what studies or other material will be included and excluded
  4. Have an established process for identifying and gathering information to be reviewed
  5. Evaluate the validity of the material being reviewed
  6. Include a process for peer review, or review by people in the same field of expertise
  7. Present a clear summary of findings that can be reviewed and replicated by others
  8. Have a summary that is written by experts who are well-versed in the field under review


What are systematic reviews? Prepared by the Cochrane Consumers and Communication Group


The Pieces

Researchers conducting a systematic review need to follow fixed yet flexible and iterative processes that describe necessary steps required to produce a rigorous synthesis of the literature.

You should document at the time all of the steps that you take to complete your review, as this allows your methodology to be compiled accurately.

It is vital to define your question and determine if any other systematic review has previously been conducted on this question. To reduce bias in a systematic review, it is vital to develop a review plan or protocol.

Steps include:

  1. Planning a systematic review
  2. Identifying studies and sources
  3. Evaluating and appraising results
  4. Collecting and combining data
  5. Explaining the synthesis
  6. Summarizing the findings

Source: Foster, M.J. and Jewell, S.T. (eds.), 2017. Assembling the pieces of a systematic review: a guide for librarians. 


Before starting, it’s important to ensure that your research question has not already been successfully answered in a recent review, and that no reviews on the topic are planned or in progress. Reviews in progress (or prospective systematic reviews) may be referred to as protocols. A protocol clearly documents what the reviewers intend to do in their systematic review.

Protocols are used to pre-establish objectives and methods for your systematic review. They should be established prior to the formal literature search to help decrease bias. Registering protocols is recommended to avoid duplication of effort. Once you've developed your protocol, register it!

PROSPERO is the International prospective register of systematic reviews in health and social care, welfare, public health, education, crime, justice, and international development. (Cochrane protocols are automatically uploaded to Prospero).

Strategies & PRISMA

Systematic reviews should be transparent and replicable, you are required to document each step as you progress. There is no one way to do this! Possibilities include using Excel or Word, keeping a journal, and creating personal database accounts for saving searches as you proceed.

Data collected should be accurate, complete, and in a format that allows for future updates and data sharing. We recommend using bibliographic software like EndNote Online.

As with any data collection and reporting process, it's worthwhile keeping in mind basic data management principles:

  • Back up work regularly in multiple locations.
  • Use filenames and systems that timecode your entries and updates, to avoid different collaborators working on different versions. Try using an electronic laboratory notebook (ELN).
  • Data planning and Data storage are crucial elements in your planning process
  • Consider making your data open. Open access data may be a requirement for some systematic review organisations or publications. Find out more about open access data from our guide.

See: Research Data Management for more information. 


Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) is an evidence-based minimum set of items for reporting in systematic reviews and meta-analyses. PRISMA focuses on the reporting of reviews evaluating randomized trials, but can also be used as a basis for reporting systematic reviews of other types of research.


Checkout the PRISMA resources: 

Where & how to search

There is no set number of resources to search; you need to ensure that the search is expansive and comprehensive and include published and (in most cases) unpublished sources. Best practice is to search more than one resource. Systematic reviews in health and medicine will often search 3-5 databases, and searching more is not unusual.

Start with identifying the key databases covering your subject area by taking a look at the databases on the appropriate subject guide, or by going directly to our Databases A-Z. Your Subject Librarian can also advise on the best ones to search.

Search Smart is a free online guide to researchers best search options

Developing a search strategy is the process of converting your research question into a format that the database can interpret. Databases work by matching the search terms that you enter to the titles, abstracts, and subject headings in the records of items in the database. To locate the relevant literature, you need to use the same terms that are used in relevant sources.

For each identified concept in your research question, make a list of relevant keywords and subject headings. Once you have identified your key concepts, identify the words most likely to have been used in the published literature on this topic. It is important to develop a comprehensive range of terms for each discrete concept entailing a combination of subject headings and a wide range of keywords/phrases for each concept. It’s crucial to develop clear inclusion and exclusion criteria.

Create and test your search strategy in a primary database, then move on to running the search in other databases you've selected for your review.

For each identified concept in your research question, make a list of relevant keywords and subject headings.See Search Tips & Advanced Search Strategies.


Cochrane Handbook for Systematic Reviews of Interventions

The official guide that describes in detail the process of preparing and maintaining Cochrane systematic reviews on the effects of healthcare interventions. By Higgins JPT, Thomas J, Chandler J, Cumpston M, Li T, Page MJ, Welch VA (editors). Cochrane, 2023.


JBI Manual for Evidence Synthesis

JBI is an international evidence-based healthcare research organisation. This manual is a comprehensive guide to conducting JBI systematic reviews. It describes in detail the process of planning, undertaking and writing up a systematic review using JBI methods.

Risk of bias checklists & tools

Systematic Review vs. Literature Review

It is common to confuse systematic and literature reviews as both are used to provide a summary of the existing literature or research in a specific area.



Table from: Robinson, P. and Lowe, J., 2015. Literature reviews vs systematic reviews. Australian and New Zealand journal of public health39(2), pp.103-103.


Other types of reviews

For information on other types of reviews see: A typology of reviews: an analysis of 14 review types and associated methodologies. Health Information & Libraries Journal, 26: 91-108. doi:10.1111/j.1471-1842.2009.00848.x

Tutorials & training


Cochrane Training

Learning resources relevant to systematic reviews and evidence-based medicine.

Learn how to search systematically for information that you might need for research, for a literature review, publication, or report.

Training & Support

Your subject librarian is available to consult with researchers and offer training to:

  • Develop or refine review topics
  • Identify existing systematic reviews on a topic
  • Recommend appropriate databases
  • Review and develop search strategies to ensure all relevant studies are identified 
  • Advise on a citation management software
  • Advise on options for locating the full text of articles

External training: Evidence Synthesis Ireland (ESI) Training & Webinars