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Doing a Systematic Review

A concise guide to the steps involved in systematic, scopic and related reviews

Your research question

Light bulb in a thought bubbleYour first step is to devise a focused, clear research question which your review will address. Most people use a framework to help them devise this question.

You may wish to do some "trial run" scoping searches of a database to find out how much has been written, and what limits you should apply. Web of Science (Core Collection) is good for this, as it includes articles from most disciplines; it is also available in most institutions, so if you are working with non-Trinity colleagues, they should have access as well.

It's not unusual for the research question to change, if it looks like the amount of results will be too many or too few. For postgraduate level, a few thousand results in Web of Science might be the roughly appropriate amount.

PICO framework for structuring your research

There are several different frameworks you can use to help structure your research and ensure you have clear parameters for your search. The most commonly used one used for health-related reviews is the PICO framework:

  • Population
    This could be the general population, or a specific group defined by: age (e.g. infants, children, adolescents, elderly); socioeconomic status (e.g. low-income, homeless); risk status; location (rural or urban)
  • Intervention
    Refers to the therapy, test, strategy to be investigated (e.g. drug, behavioural change, environmental factors, counselling)
  • Comparator
    A measure you will use to compare results against (e.g. no treatment, alternative treatment/exposure, standard/routine interventions)
  • Outcome
    What outcome is significant to your population or issue? This may be different from the outcome measures used in the studies.
PICO example
Review title The effect of blueberries on cognition and mood: a systematic review of human intervention trials
Population Individuals of all ages, without regard to gender, race or ethnicity. 
Intervention Supplementation with blueberries, relevant blueberry products or extracts from blueberries. This may include freeze-dried blueberries, blueberry concentrate, or blueberry juice.
Comparator Placebo or control groups.
Outcome Changes in cognitive function based on cognitive screening measures (such as Mini mental state examination, Montreal Cognitive Assessment), neuropsychological interview, informant/carer responses to assessment tools or changes in mood. Secondary outcomes include: changes in biochemical levels in biological fluids. Of particular interest are inflammatory markers, cardiovascular disease risk factors, and markers of gastrointestinal health. 

This example is extracted from: PROSPERO 2018 CRD42018100888.

Further information

Alternative frameworks

Another framework may be more suitable depending on your review topic. Here are some other options:

  • PECO – Population | Environment | Comparison | Outcome
    Very similar to PICO but looking at the effect of exposure to something e.g. smoky atmosphere
  • SPICE - Setting | Population | Intervention | Comparison | Evaluation
    Another variant of PICO but this time including the setting (where? in what context?)
  • CIMO - Context | Intervention | Mechanisms | Outcome
    A variant of PICO suitable for management and organisation studies
  • ECLIPSE - Expectation | Client group | Location | Impact | Professionals | SErvice
    Recommended for health policy/management searches
  • SPIDER – Sample | Phenomenon of Interest | Design | Evaluation | Research Type
    Developed to create effective search strategies of qualitative and mixed-methods research - more specific than PICO/PECO
Further information

Creating a protocol

Now you have framed your question, you should develop a protocol - a statement of intent on what you plan to do in the systematic review. You won’t have your findings yet, but you know  what you are (likely) to do... a draft version with some of the details planned out. It isn’t set in stone – what you do can change when you actually do the systematic review; but this is noted in the SR.

Publishing a protocol also deters others from doing exactly the same review, even if you haven’t published yet!

A protocol outlines the study methodology, including:

  • background
  • research question and aims
  • criteria for inclusion and exclusion
  • methods including:
    • search strategy
    • selecting studies for inclusion
    • quality assessment
    • data extraction & analysis
    • synthesis of results
    • dissemination
  • time frame.
Note - if you have started “extraction” of results then it’s moved beyond the protocol stage.
There are various registers and repositories for protocols and SRs – PROSPERO, Cochrane Library, JBI and Campbell Collaboration are the most well-known. If you are looking at a different type of review (scoping, for example), you might consider OSF.