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Systematic reviews: The question

The review question

  • The question for a systematic review needs to be very clearly defined. What are you trying to achieve and why?
  • A 'fluffy' (unclear) question is difficult to search, screen or extract relevant information on, and is unlikely to succeed.
  • Some prior research is required to ensure the question hasn't already been done, and that it is manageable - not too big and not too small.
  • Although some review questions use a specific framework such as PICO, this isn't essential.

The review question - things to consider

  • Has the question already been answered?
  • What is the purpose of asking this question?
  • What will this question add to the existing literature?
  • Is it helpful to use a question framework such as PICO or SPIDER? 
  • How will concepts in the question be defined? For example:
    • How will adult be defined? What age range is this? 18 to 64? 18 plus? 21 plus?
    • How will diabetes be defined? Does it include type 1, type 2, pre-diabetes?
  • Does the question limit to a particular type of study, such as RCTs?
  • Does the question involve quantitative, qualitative or mixed method publications? 
  • What is in or out of scope? What will the inclusion and exclusion criteria be?
  • Does the question involve a specific timeframe (limiting by date)? If so, why?

The review question - potential frameworks

It is not essential to follow a question framework, but it may be useful. Remember that every concept in a framework is not always replicated in a search strategy, as it can make the search too tight. 

Some question frameworks:

  • PICO - Patient | Intervention | Comparison | Outcome
  • PECO – Population | Environment | Comparison | Outcome
  • SPIDER - Sample | Phenomenon of Interest | Design | Evaluation | Research type
  • SPICE - Setting | Perspective | Intervention | Comparison | Evaluation

Learn more:

The review question - how library staff can help

Library staff can assist with searching for existing review papers. Please note that this is a quick search where strategies are not provided. It is not a structured search for the systematic review itself.

The review question - common pitfalls and how to avoid them

Many systematic reviews don't make it over the finish line. These are some of the reasons we have experienced as co-authors:

Review team cannot agree on details or keeps expanding the question

The problem:

  • Can create a "fluffy" topic that is too wide, badly defined and understood, and which changes.
  • Even slight shifts in the question are likely to require new search strategies and starting over.
  • Consumes a great deal of time as each version of the question is explored.
  • As the review becomes too difficult the team may lose interest in proceeding.

How to avoid:

  • Don't start work on the review proper (including searches) until consensus has been reached. 
  • Make a decision and stick to it.
  • Write and register a protocol. Lock it in!

The question has already been answered before you publish

The problem:

  • Another systematic review on the same topic may be discovered during the searches - either initially or during updates.
  • If there are long delays (especially with screening) another review might be published first.

How to avoid:

  • Carry out an initial scoping search for existing reviews before writing a protocol.
  • Search PROSPERO for an existing protocol.
  • Ensure that the team is committed to screening in a timely way to avoid delays.
  • If another review is discovered towards the end of the process, consider whether there is anything new to add that is likely to be accepted by a journal. All may not be lost!

Guide Author

Helen Wilding, Senior Research Librarian

Carl de Gruchy Library, St Vincent's Hospital Melbourne

Literature Searching, Systematic Reviews, Mental Health liaison 
Thursdays, Fridays & alternate Wednesdays
Helen's profile | Researchgate | Orcid