Literature Reviews: Systematic & Narrative: Protocols, PRISMA & PICO

One of the distinguishing features of a systematic review is the predetermined, transparent and replicable approach that is taken to conduct the research.  Systematic reviews are typically a standalone research and need to be conducted with the same rigour as other primary research.

This approach or method is written up in your protocol and is one of the early steps in your review process as it needs to be done before the review.  If you are aiming to publish, you will want to publish your protocol online and it is a good idea to do this for any type of review you are doing that is following a systematic process. 

Your protocol will outline and justify:

• The search question such as your PICO elements
  • Population
  • Intervention
  • Comparison
  • Outcomes
• Inclusion and exclusion criteria e.g.:
  • Study types (e.g. Randomised control trials)
  • Date range
  • Clinical setting or lens
  • Specifics of the population
• Any potential or mitigation of bias
• The databases searched and the search strategy employed.
• How the information will be grouped for analysis

For further information see the sources linked below.

Have a look to see how other people have written a protocol

Before starting out on your review, one of the best things you can do is look at what other people have done.  In terms of looking at other people's protocols try PROSPERO (linked below) and using the JBI database's Publication Type limiter: Systematic Review protocol.

If you can get something related to your topic, great, it will help confirm the best databases to use and potentially give you some other ideas, however, it won't matter if it is on a different topic, it is more about looking at the types of things that are included in a protocol and how to lay it out.

Staff and students also have access to the JBI SUMMARI software as part of our subscription to JBI, this includes a protocol template.  See the relevant box on the Software & AI page for more information.

Inclusion and exclusion criteria are a critical part of the systematic review process. Ideally, these criteria should be clearly defined in your protocol and methods section before beginning your review. Preliminary searching can help refine the most appropriate criteria to use.

Purpose of Inclusion/Exclusion Criteria:

• Enable broad searching initially, followed by focused screening based on the criteria.
• Minimise selection bias by ensuring studies are included based on predefined, objective standards.
• Align with your question framework, typically based on:
  • Population
  • Intervention (or area of interest)
  • Outcomes

Additional common elements to consider in your inclusion/exclusion criteria include:

• Date range
• Geographic location
• Context or setting
• Language
• Types of study design or publication

PRISMA (which stands for Preferred Reporting Items for Systematic Reviews and Meta-Analysis) is a reporting guideline for systematic reviews and meta-analyses. 

Most systematic reviews will include a PRISMA chart and this guides the steps taken within the search process which enhances the transparency of the review.

Here is an example (taken from the PRISMA 2020 downloadable Flow Diagram) 

This work is licensed under CC BY 4.0. To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/

PRISMA charts differ between reviews, have a look at reviews others have done to get an idea of how they can be utilised.  They are often much simpler than the above example.  Here is one that had been generated from the Haddaway et al. (2022) PRISMA Flow Diagram tool.

Haddaway, N. R., Page, M. J., Pritchard, C. C., & McGuinness, L. A. (2022). PRISMA2020: An R package and shiny app for producing PRISMA 2020-compliant flow diagrams, with interactivity for optimised digital transparency and open synthesis. Campbell Systematic Reviews, 18, e1230. https://doi.org/10.1002/cl2.1230

PICO

One of the things you will see mentioned a lot in the world of systematic reviews, is PICO (particularly in health areas).  This is a framework for structuring a research question.  It can help to ensure that you clearly define the research question, it helps you to organise the concepts into a comprehensive search strategy, and assists with the defining of inclusion and exclusion criteria which in turn improves the consistency and transparency of a review.

PICO stands for:

For our hypothetical research question looking at: Effectiveness of social media interventions on the eating behaviours of teenagers, our PICO might look something like:

For this particular question we don't have a comparator as we aren't comparing two interventions - this is not uncommon, so really in this case, we'd be using a PIO structure.  Sometimes the I might stand for area of Interest. There are other variations on PICO for example:

• PICOT: where T stands for timeframe.  
• PICOC: where C stands for context
• PECO: where E stands for Exposure

Many of you will be doing non-clinical reviews and/or reviews on qualitative topics, in which case, PICO might not fit your needs.  Don't worry, there are other frameworks out there to consider, see the box in this guide called "Alternative Question Frameworks" .

Further Reading