What is a systematic review?
"A systematic review attempts to collate all empirical evidence that fits pre-specified eligibility criteria to answer a specific research question. It uses explicit, systematic methods that are selected to minimize bias, thus providing reliable findings from which conclusions can be drawn and decisions made... Meta-analysis is the use of statistical methods to summarize and combine the results of independent studies." - Cochrane Collaboration
Writing your protocol
Before carrying out your systematic review, make sure to consult at least one set of guidelines (e.g. PRISMA, Cochrane) to help develop your protocol. Also, it is strongly recommended that you register your review with PROSPERO to help make sure the same search question wasn't or isn't currently being investigated by others.
PRISMA stands for Preferred Reporting Items for Systematic Reviews and Meta-Analyses. It is an evidence-based minimum set of items for reporting in systematic reviews and meta-analyses. The PRISMA Statement consists of a 27-item checklist and a four-phase flow diagram (available as PDF files in the right-hand column).
- Cochrane Handbook for Systematic Reviews of Interventions
The official document that describes in detail the process of preparing and maintaining Cochrane systematic reviews on the effects of healthcare interventions.
- Institute of Medicine: Finding What Works in Health Care
The IOM recommends 21 standards for developing high-quality systematic reviews of comparative effectiveness research. The standards address the entire systematic review process from the initial steps of formulating the topic and building the review team to producing a detailed final report that synthesizes what the evidence shows and where knowledge gaps remain.
Formulating the question
Construct a narrow foreground question using the PICO format (worksheet available in right-hand column). Or, use the following formula as a template:
In patients [include any significant demographics]
with [specify Problem]
does [specify Intervention] or [specify Comparison, if any]
affect [specify Outcome]?
The type of studies you should include in your literature search will depend on the type of question being asked:
|Question Type||Suggested Study Types|
|Diagnosis||RCTs > prospective studies|
|Therapy||RCTs > cohort studies > case-control studies|
|Etiology||RCTs > cohort studies > case-control studies|
|Prognosis||cohort studies > case-control studies|
Initial search considerations
- Decide which databases to search: general biomedical databases (PubMed/MEDLINE, Scopus, ClinicalTrials.gov) and/or subject-specific databases (PsycINFO, ERIC).
- Develop a list of keywords and subject headings for each concept in your question. Search engines are only as smart as you tell them to be! You will have to think of all the synonyms that could be used to describe each concept in your question, because different authors may use different terms for the same condition or population (e.g. heart attack / myocardial infarction / cardiovascular stroke).
- Computers operate using mathematical language, so you will have to combine your search terms in a certain order (using AND, OR, NOT), use quotes around phrases, parentheses around separate concepts, truncation symbols, etc.
Managing your results
- For each database searched, save the exact search strategy used, date of search, and number of results.
- Save the list of results in Excel format (XLS, TXT) and/or the format required for your citation management progam (EndNote, Zotero).
For more information about these programs, check out our Citation Management guide.
Need help searching?
Contact a librarian if you would like some help searching for information on your topic or tracking down the full text of an article. That's why we're here!