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University of Washington Health Sciences Library

Systematic Reviews and other evidence synthesis projects

Developing your Question

Developing your research question is one of the most important steps in the evidence synthesis process. At this stage in the process, you and your team have identified a knowledge gap in your field and are aiming to answer a specific question:

  • If X is prescribed, then Y will happen to patients?

OR assess an intervention:

  • How does X affect Y?

OR synthesize the existing evidence

  • What is the nature of X? ​

​​Whatever your aim, formulating a clear, well-defined research question of appropriate scope is key to a successful evidence synthesis.

The research question will be the foundation of your synthesis. From it your research team will identify 2-5 possible search concepts. Later, you will use these search concepts to build your search strategy. 

The nature of your question will help you figure out what type of evidence synthesis to write: Do you have a focused research question with narrow parameters? You may want a systematic review, especially if it fits into the PICO question format. Do you have a broad question that looks at answering larger, more complex, exploratory research questions? You may want a scoping review.
Remember that one type of review is not inherently better: they each serve different purposes. But all will benefit from planning and documenting your process.

Research Question Frameworks

Formulating a research question takes time and your team may go through different versions until settling on the right research question. To help formulate your research question, some research question frameworks are listed below.


The PICO model is probably the most commonly-used framework, especially for clinical research questions:

  • Patient or Population in relation to the Problem
    • What are the characteristics of the patient or population?
    • What is the condition, disease, or situation you are interested in?
  • Intervention or exposure
    • What is the intervention, test, or exposure you want to find out about in relation to the patient/population/problem?
  • Comparison (not always applicable)
    • What is the alternative to the intervention (e.g. placebo, different drug, surgery)?
    • If the alternative is usual care or no intervention, skip Comparison
  • Outcome
    • What are the relevant outcomes (e.g. morbidity, death, complications, quality of life)?

Example: Is gabapentin (intervention), compared to placebo (comparison), effective in decreasing pain symptoms (outcome) in middle aged male amputees suffering phantom limb pain (population)?

Sometimes the model is described as PICO(T), where the T stands for Time or for Type of Study (the study design(s) most appropriate to answer the question).

While PICO is a helpful framework for clinical research questions, it may not be the best choice for other types of research questions, especially outside the health sciences. Here are a few others:

PICo for Qualitative Studies

  • P       Population/Problem
  • I         Phenomenon of Interest
  • Co    Context

Example: What are the experiences (phenomenon of interest) of caregivers providing home based care to patients with Alzheimer's disease(population) in Australia (context)?


  • S    Setting
  • P   Perspective (for whom)
  • I    Intervention/Exposure
  • C   Comparison
  •  Evaluation

Example: What are the benefits (evaluation) of a doula (intervention) for low income mothers (perspective) in the developed world (setting) compared to no support (comparison)?


  • S     Sample
  • PI   Phenomenon of Interest
  • D    Design
  • E     Evaluation
  • R    Study Type

Example: What are the experiences (evaluation) of women (sample) undergoing IVF treatment (phenomenon of interest) as assessed?
Design: questionnaire or survey or interview
Study Type: qualitative or mixed method


There are dozen of different types of these frameworks For a table of other common types, see this guide from the University of Maryland: For a comprehensive but concise overview of the almost 40 different types of research question frameworks, see this review from the British Medical Journal: Rapid review of existing question formulation frameworks

¹Published as supplemental material to Booth A, Noyes J, Flemming K, Moore G, Tunçalp Ö, Shakibazadeh E. Formulating questions to explore complex interventions within qualitative evidence synthesis. BMJ Glob Health. 2019;4(Suppl 1):e001107. Published 2019 Jan 25. doi:10.1136/bmjgh-2018-001107.

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