What to know
- A systematic review attempts to collect and analyze all evidence that answers a specific question.
- Learn about what is involved with conducting a systematic review of the literature for evidence-based public health and how the library supports the process.
How can the library help?
Several CDC librarians have special training in conducting literature searches for systematic reviews. Literature searches for systematic reviews can take a few weeks to several months from planning to delivery.
Fill out a search request form or contact the Stephen B. Thacker CDC Library by email (cdclibrary@cdc.gov) or telephone (404-639-1717).
What is a systematic review?
A systematic review attempts to collect and analyze all evidence that answers a specific question. The question must be clearly defined and have inclusion and exclusion criteria. A broad and thorough search of the literature is performed and a critical analysis of the search results is reported and ultimately provides a current evidence-based answer to the specific question.
What does it take to do a systematic review?
Time: According to Cochrane, it takes 18 months on average to complete a Systematic Review.
The average systematic review from beginning to end requires 18 months of work. "...to find out about a healthcare intervention it is worth searching research literature thoroughly to see if the answer is already known. This may require considerable work over many months..." (Cochrane Collaboration)
Review Team: Team Members at minimum:
- Content expert
- 2 reviewers
- 1 tie breaker
- 1 statistician (meta-analysis)
- 1 economist if conducting an economic analysis
- *1 librarian (expert searcher) trained in systematic reviews
"Expert searchers are an important part of the systematic review team, crucial throughout the review process—from the development of the proposal and research question to publication." (McGowan & Sampson, 2005)
*Ask your librarian to write a methods section regarding the search methods and to give them co-authorship. You may also want to consider providing a copy of one or all of the search strategies used in an appendix.
The Question to Be Answered: A clearly defined and specific question or questions with inclusion and exclusion criteria.
Written Protocol: Outline the study method, rationale, key questions, inclusion and exclusion criteria, literature searches, data abstraction and data management, analysis of quality of the individual studies, synthesis of data, and grading of the evidience for each key question.
Literature Searches: Search for any systematic reviews that may already answer the key question(s). Next, choose appropriate databases and conduct very broad, comprehensive searches. Search strategies must be documented so that they can be duplicated. The librarian is integral to this step of the process. Before your librarian creates a search strategy and starts searching in earnest you should write a detailed PICO question, determine the inclusion and exclusion criteria for your study, run a preliminary search, and have 2–4 articles that already fit the criteria for your review.
What is searched depends on the topic of the review but should include
- At least 3 standard medical databases like PubMed/Medline, CINAHL, Embase, etc.
- At least 2 grey literature resources like Clinicaltrials.gov, COS Conference Papers Index, Grey Literature Report, etc.
Citation Management: EndNote is a bibliographic management tools that assist researchers in managing citations. The Stephen B. Thacker CDC Library oversees the site license for EndNote.
To request installation: The library provides EndNote to CDC staff under a site-wide license. Please use the ITSO Software Request Tool (SRT) and submit a request for the latest version (or upgraded version) of EndNote. Please be sure to include the computer name for the workstation where you would like to have the software installed.
EndNote Training: CDC Library offers training on EndNote on a regular basis—both a basic and advanced course. To view the course descriptions and upcoming training dates, please visit the CDC Library training page.
For assistance with EndNote software, please contact endnote@cdc.gov
Vendor Support and Services: EndNote – Support and Services (Thomson Reuters) EndNote – Tutorials and Live Online Classes (Thomson Reuters)
Getting Articles:
Articles can be obtained using DocExpress or by searching the electronic journals at the Stephen B. Thacker CDC Library.
Literature searching for a systematic review
The goal of a systematic review search is to maximize recall and precision while keeping results manageable. Recall (sensitivity) is defined as the number of relevant reports identified divided by the total number of relevant reports in existence. Precision (specificity) is defined as the number of relevant reports identified divided by the total number of reports identified.
Issues to consider when creating a systematic review search:
- All concepts are included in the strategy
- All appropriate subject headings are used
- Appropriate use of explosion
- Appropriate use of subheadings and floating subheadings
- Use of natural language (text words) in addition to controlled vocabulary terms
- Use of appropriate synonyms, acronyms, etc.
- Truncation and spelling variation as appropriate
- Appropriate use of limits such as language, years, etc.
- Field searching, publication type, author, etc.
- Boolean operators used appropriately
- Line errors: when searches are combined using line numbers, be sure the numbers refer to the searches intended
- Check indexing of relevant articles
- Search strategy adapted as needed for multiple databases
Search instructions and checklists
- Cochrane Handbook: Searching for Studies See Part 2, Chapter 6
Leenaars M., et al. (2011). Laboratory Animals, 46(1): 24-31. PMID: 22037056.
Tips
Look for systematic reviews that have already been published
- To ensure that the work has not already been done.
- To provides examples of search strategies for your topic.
Look in PROSPERO for registered systematic reviews.
Search Cochrane and CRD-York for systematic reviews.
Search filter for finding systematic reviews in PubMed
Disclaimer
Materials listed in these guides are selected to provide awareness of quality public health literature and resources. A material’s inclusion does not necessarily represent the views of the U.S. Department of Health and Human Services (HHS), the Public Health Service (PHS), or the Centers for Disease Control and Prevention (CDC), nor does it imply endorsement of the material’s methods or findings. HHS, PHS, and CDC assume no responsibility for the factual accuracy of the items presented. The selection, omission, or content of items does not imply any endorsement or other position taken by HHS, PHS, and CDC. Opinion, findings, and conclusions expressed by the original authors of items included in these materials, or persons quoted therein, are strictly their own and are in no way meant to represent the opinion or views of HHS, PHS, or CDC. References to publications, news sources, and non-CDC Websites are provided solely for informational purposes and do not imply endorsement by HHS, PHS, or CDC.