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Systematic Review: Formulate the review question

How to carry out a systematic review of the literature.

Formulate the review question

Depending on your subject area, you may find the PICO (Participants, Interventions, Comparisons and Outcomes) model helpful in formulating your question.

  • Participants, Patient Population or Problem– who is the question about, for example gender, age, ethnicity, disease type, co-morbidity of the patient(s)?
  • Intervention, Indicator or Exposure – which test, treatment, drug, procedure are you interested in?
  • Comparisons, comparator, control or context – is there an alternative intervention you want to make a comparison with? What is the context?
  • Outcomes – what you hope to achieve, or avoid? You may not need to answer all of these areas and you may also want to include the setting and the study design.

Alternatives to PICO

You may not find the PICO method applicable, and if this is the case SPICE or SPIDER might be helpful.


  • Setting - this is the context for your question, the where?
  • Perspective - what is the perspective of your stakeholders, or future users of the service or product?
  • Intervention - what action is being taken?
  • Comparison - are there other alternative actions or outcomes?
  • Evaluation - what is the outcome measure?


  • Sample - you sample size may vary, but it can be useful to define at the start of your review
  • Phenomenon of Interest - consider interventions, behaviors and experiences which may be relevant
  • Design - study design can impact on the robustness of research
  • Evaluation - what are the outcome measures? are they anecdotal? is this more relevant?
  • Research type - what research types are relevant?


You should also prepare a protocol. This is a plan of what you are going to do, what you will include and exclude and what methods you will use.
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