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Doing a systematic review

Guidance on the steps involved in doing a systematic review, and ways in which the Library can help.

Creating a protocol

Light bulb in a thought bubbleYour first step is to devise a focused, clear and answerable question which your review will address.

This may be revised as you work through the next step which is to develop a protocol which outlines the study methodology including:

  • background
  • research question and aims
  • criteria for inclusion and exclusion - these specify attributes which selected studies must have, or attributes which will disqualify them. They must be sufficiently clear and detailed to enable you to accurately assess the relevance of each study.
  • methods including:
    • search strategy
    • quality assessment
    • data extraction & analysis
    • synthesis of results
    • dissemination
  • time frame.

Whilst you are in the early stages of choosing and defining your research question try doing some scoping searches, using simple search terms, on a couple of relevant databases. These will help you identify key papers, boost your understanding of the topic, and give you a feel for how many studies have been done. If there are too few results how can your broaden your search? If too many, can you focus in on a specific aspect or population, or apply limits such as study type or publication date?

It is important to discuss your protocol with your supervisor to get their expert opinion on the way you have framed your study.

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

Registering your protocol

If you are doing a systematic review for potential publication then it is a good idea to register it with one of the following sites. This helps ensure you are not duplicating an existing study. Also by registering the protocol prior to starting your research there is a reduced risk of reframing the study to fit the results.

Sites only accepting reviews
Sites accepting any type of study

Both these sites accepts all study designs in any field. Both are free to register. Unlike the previously mentioned sites there is no checking of records.

Further information

The following resources give more information about why it is important to register your review protocol and the sites which are currently available.