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Systematic reviews

A brief overview of systematic reviews and resources to support producing one.

Formulating a clear and concise question

General principles

"A good systematic review is based on a well formulated, answerable question. The question guides the review by defining which studies will be included, what the search strategy to identify the relevant primary studies should be, and which data need to be extracted from each study."

A systematic review question needs to be

  • Clear
  • Focussed
  • Specific

You may find it helpful to use a search framework, such as those listed below, to help you to refine your research question, but it is not mandatory. Similarly, you may not always need to use every aspect of the framework in order to build a workable research question.

Counsell C. Formulating questions and locating primary studies for inclusion in systematic reviews. Ann Intern Med. 1997;127(5):380–387.

PICO framework

To help formulate a focussed research question the PICO tool has been created. PICO is a mnemonic for Population, Intervention, Comparison, and Outcome. These elements have been highlighted to help define the core elements of the question which will be used in the literature search.

The elements of PICO


Who or what is the topic of interest, in the health sciences this may be a disease or a condition, in the social sciences this may be a social group with a particular need.


The intervention is the effect or the change upon the population in question. In the health sciences, this could be a treatment, such as a drug, a procedure, or a preventative activity. Depending on the discipline the intervention could be a social policy, education, ban, or legislation.


The comparison is a comparison to the intervention, so if it were a drug it may be a similar drug in which effectiveness is compared. Sometimes the comparator is a placebo or no comparison.


The outcomes in PICO represent the outcomes of interest for the research question. The outcome measures will vary according to the question but will provide the data against which the effectiveness of the intervention is measured.

Other search frameworks

Not all systematic review questions are well served by the PICO mnemonic and a number of other models have been created, these include:  ECLIPSE (Wildridge & Bell, 2002), SPICE (Booth, 2004), and SPIDER (Cooke, Smith, & Booth, 2012).

ECLIPSE - used to define search terms for health & social care management, services or policies.
E C L I P Se


What innovation, improvement, or information is required?

Client group

What client group is the service aimed at?


Where is the client group or service located?


What are the desired outcomes & how may they be measured?


Who is involved in delivering/improving the service?


What service will this inform?

Wildridge V, Bell L. How CLIP became ECLIPSE: a mnemonic to assist in searching for health policy/ management information. Health Info Libr J. 2002;19(2):113–115.

SPICE - useful when examining a service, intervention, or policy.


What is the context for your question?


Who is the service/product aimed at?

What is the perspective of your stakeholders or future users of the service/product?


What action is being undertaken?


Are there other/alternative actions or outcomes?


What is the result/outcome being measured?

Booth A. Clear and present questions: formulating questions for evidence based practice. Library Hi Tech. 2006;24(3):355-368.

SPIDER - useful when searching for qualitative or mixed methods studies.


Sample size may vary.

Phenomenon of Interest

Consider interventions, behaviours, and experiences that may be relevant.


Study design can impact the robustness of research.


What are the outcome measures?


Research type

What research types are relevant?


Cooke A, Smith D, Booth, A. Beyond PICO: the SPIDER tool for qualitative evidence synthesis. Qual Health Res. 2012;22(10):1435–1443.

Remember: you do not have to use a search framework but it can help you to focus your research question and identify the key concepts and terms that you can use in your search. Similarly, you may not need to use all of the elements in your chosen framework, only the ones that are useful for your individual research question.