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Steps in conducting a systematic review

  • Define the question - a clearly defined question will ensure that your research produces relevant results.
  • Define the protocol, which includes the inclusion/exclusion criteria. This defines the process for selecting studies.
  • Develop the search strategy.
  • Identify any recent or ongoing systematic reviews.
  • Search relevant sources to identify the evidence.
  • Appraise and select suitable studies.
  • Synthesise the data.
  • Document the search process.

The PICO structure can be used to help you put together a search strategy and formulate the question:

      Participants, Patient or Population       

      Intervention(s) (therapy, treatment, etc.)

      Comparision (other intervention or treatment, no treatment, etc.)


In some cases the review question may also include the Study Design (PICOS). This is outlined in the Centre for Reviews and Dissemination, University of York, guide “Systematic reviews: CRD's guidance for undertaking reviews in health care”:

“The review question can be framed in terms of the population, intervention(s), comparator(s) and outcomes of the studies that will be included in the review. These elements of the review question, together with study design, will then be refined in order to determine the specific inclusion criteria that will be used when selecting studies for the review.”

"Not every review question will specify type of study design to be included". See Levels of Evidence page for hierarchy of study design.

It is important when searching for evidence that search terms are referred back to your original PICO question. The process of finding evidence follows these steps: 

1. Identify terms to fit your PICO question. These keywords will be used in searching databases. Check thesaurus terms in the relevant databases to identify other relevant keywords or subject terms to include in your search. Be aware of differences in American and English spelling and terminology. Thesaurus terms may also vary between databases. For health fields, you can use tools such as PubReminer to help you determine the most commonly used keywords in a database

2. Find systematic reviews - it's helpful to find out if a systematic review has been done or is under way. Published reviews also provide a starting point for identifying the studies.

3. Find journal articles - search for published primary studies in databases such as MEDLINE, CINAHL, PsycINFO. Citation searching in Scopus or Web of Science, allows you to follow a research trail forwards, backwards or to related research.

4. Search the Grey Literature, such as conference proceedings, theses, reports and unpublished literature.

5. Appraisal and selection of studies. Structured appraisal helps to select the highest quality of evidence available and minimise bias.  

6. Synthesis of study results. Data from each individual study needs to be collated, combined and summarised. Quantitative systematic reviews use formal statisitical techniques such as meta-analysis to perform this step.

"As well as drawing results together, synthesis should consider the strength of evidence, explore whether any observed effects are consistent across studies, and investigate possible reasons for any inconsistencies" (Centre for Reviews and Dissemination, 2009, section 1.3.5). Systematic reviews: CRD's guidance for undertaking reviews in health care  

The search process needs to be documented in enough detail to ensure that it can be reported correctly in the review and reproduced for verification. Here is a worksheet that may be helpful to use in documenting your progress.

For each database search record:

  • Database searched
  • Database provider (e.g. EBSCO)
  • Search strategy - keywords used and how these were combined in the search
  • Years searched
  • Date search was run
  • Any filters used
  • Number of studies identified

EndNote software can be used to record full bibliographical details for each citation and additional notes relating to the selection and evaluation of that  source.

Yale University Medical School Systematic SearchesFor a more detailed look at the systematic review search process, please see Yale University Medical Library's series of videos which break down each step.

Click the image to go to their site.