Systematic Reviews & Meta-Analyses: Home

"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

I. Before carrying out your systematic review, search the literature (in PubMed, Scopus, Google Scholar, etc.) for any systematic reviews that have already been published on your topic or related to your topic. The benefits are two-fold:

(1) helps to ensure that the work has not already been done (if it has, you can re-formulate your topic)
(2) provides examples of search strategies used for your topic or for parts of your topic.

NOTE: You should also search for other types of studies on your topic to make sure there is enough literature to conduct a systematic review. For example, for intervention or therapy studies, for which randomized controlled trials are the gold standard in terms of evidence, you want to find at least a few RCT's on your topic to make sure a full systematic review is feasible.

II. It is strongly recommended that you register your review with PROSPERO to help make sure the same search question wasn't / isn't being investigated by others and that no one else will start a systematic review on this topic while you're conducting one.

III. As obvious as it sounds, a systematic review / meta-analysis must be conducted in a systematic manner, and a well-defined and well-constructed protocol will get you started on the right foot! Make sure to consult at least one set of guidelines (e.g. PRISMA, Cochrane) to help develop your protocol:

• PRISMA
  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.

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]?

For example: In patients with type 2 diabetes, does a low-carbohydrate diet or a low-fat diet improve metabolic control and quality of life?

The type of studies you should include in your literature search will depend on the type of question being asked:

• Decide which databases to search: general biomedical databases (PubMed/MEDLINE, Scopus/EMBASE, CINAHL), subject-specific databases (PsycINFO, ERIC), and/or grey literature (ClinicalTrials.gov, Conference Proceedings Index, Dissertations). 
   
• 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). HINT: Use the Concept Table to help construct your list of terms.
   
• 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.

• 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.

Use these forms to better define your own research question and search strategy.