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Systematic Review Process: best practices

Definitions, terms & purpose

More than in every other search, Systematic Review requires a " literature for inclusion" search.  This means that it is highly advisable to ensure a well formulated and specific research question as the basis of the process.   If your search question is too broad you will be overwhelmed with results and never be able to sift through all of them. If you haven't searched for similar topics by other authors to see how they have referred to the same concepts and what terminology they have used, then you may miss relevant papers.  If you haven't broken your search question down into separate concepts to have a clear view of the main terms, it will be difficult to search the databases effectively and to appropriately combine your search terms.  

Identify your research question

  1. Define your terminology -> What is the topic of your search, and it's main concepts
  2. Complete a quick search to understand the terminology/keywords/language of your subject -> Use key papers & Indexes/Thesauri used by databases to identify keywords & synonyms
  3. Formulate a clear, well-defined research question of appropriate scope -> Find existing reviews on your topic to understand better key points, identify gaps, and confirm that you are not duplicating the efforts of previous reviews

Think of it as an in-depth attempt to answer a specific, focused question in a systematic way

Use a question framework

You can use a research framework to help structure your research and ensure you have clear parameters for your search.  The PICO (Patient, Intervention, Comparison, Outcome) framework is commonly used to develop focused clinical questions for quantitative systematic reviews.

good PICO will

  • be specific and define terms and outcomes if necessary
  • investigate something new in terms of diagnosis, etiology, therapy, harm, etc.

PICO's elements represent different concepts and will guide you while framing your question: 

P – Patient | Population

Most important characteristics of patients. Examples: Gender, age, and disease or condition

I – Intervention or exposure

Main intervention. Examples: Drug treatment, diagnostic and screening test

C – Comparison or control

Main alternative. Examples: Standard therapy, placebo, no treatment, and a gold standard

O – Outcome

What you are trying to accomplish, improve, measure, affect. Examples: Reduced mortality or morbidity, and improved memory

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 (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)

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

  • E   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


Developing Your Research 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 A is prescribed, then B will happen to patients?

OR assess an intervention:

  • How does A affect B?

OR synthesize the existing evidence

  • What is the nature of A? ​

​​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 and from it your research team will identify 2-5 possible search concepts. These search concepts will later be used in step 5 to build your search strategy.