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Introduction to systematic reviews

Finding existing systematic reviews

Before you start work on your systematic review, you should check whether there are any existing or ongoing systematic reviews on your topic area. To do this, you can check the below sources of systematic reviews.

It's also a good idea to undertake some preliminary scoping searches, which will help you to identify whether your topic area is suitable and to give you an estimate of the volume of literature that is available.

Defining your question: PICO and other frameworks

An important first step of your systematic review is to define and develop your review question to ensure that your review is sufficiently focused, manageable and relevant to the outcomes that you have identified.

There are various frameworks you can use to define your review question. These provide a structure for the review question and will help you identify the concepts that will ultimately be used when developing your search strategy.


The key one used in the health sciences for clinical questions is PICO (Patient - Intervention - Comparison - Outcome) (Richardson et al., 1995).

P: Patient or Problem: Who is the patient? What are the most important characteristics of the patient? What is the primary problem, disease, or co-existing condition?

I: Intervention: What is the main intervention being considered?

C: Comparison: What is the main comparison intervention?

OOutcome: What are the anticipated measures, improvements, or affects?


Other mnemonics which can be used to frame your search strategy include:

ECLIPSE (Expectation – Client group – Location – Impact ‐ Professionals involved – SErvice). Useful for health management, health policy topics (Wildridge and Bell, 2002)

PEO (Population – Exposure – Outcome). Useful for qualitative research (Moola et al., 2015)

PICOC (Population - Intervention - Comparison - Outcome - Context) (Petticrew and Roberts, 2006)

SPICE (Setting (context) – Perspective– Intervention – Comparison – Evaluation). Useful for qualitative research topics as well as in the social sciences (Booth, 2004)

SPIDER (Sample - Phenonemon of Interest, Design, Evaluation, Research type). Useful for qualitative and mixed methods studies (Cooke et al., 2012)

You don't have to use one of these frameworks but you do need to break your search question down into the relevant concepts in order to frame your search strategy.



Booth, A. (2004) Formulating answerable questions, In: A. Booth and A. Brice (eds.) Evidence based practice for information professionals: a handbook.  London: Facet. 

Cooke, A., Smith, D. and Booth, A. (2012) Beyond PICO: the SPIDER tool for qualitative evidence synthesis, Qualitative Health Research, 22(10) 1435-1443.   

Moola, S., Munn, Z., Sears, K., Sfetcu, R., Currie, M., Lisy, K., Tufanaru, C., Qureshi, R., Mattis, P. and Mu, P. (2015) Conducting systematic reviews of association (etiology): the Joanna Briggs Institute's approach, International Journal of Evidence-Based Healthcare, 13(3) 163–169.  

Petticrew, M. and Roberts, H. (2006) Systematic reviews in the social sciences: a practical guide. Malden: Blackwell Publishing. 

Richardson, W.S., Wilson, M.C., Nishikawa, J. and Hayward, R.S. (1995) The well-built clinical question: a key to evidence-based decisions, ACP Journal Club, 123(2) A12-3.

Wildridge, V. and Bell, L. (2002) How CLIP became ECLIPSE: a mnemonic to assist in searching for health policy/management information, Health Information & Libraries Journal, 19(2) 113-115. 

Video on using the PICO framework by The Centre for Evidence-Based Medicine

This useful video, by Neal Thurley from the Bodleian Health Care Libraries, provides a succinct overview of using the PICO framework with an example search.

Creating your review protocol

You will need to develop a review protocol which is the roadmap for your systematic review. This includes the formulation of a clear research question which the systematic review can then aim to answer and establishing the inclusion and exclusion criteria  Having a clearly defined question and explicit search parameters are fundamental to a successful systematic review. This will enable you to formulate your search strategy and then, once you have run your searches, evaluate and select the studies for inclusion.

An example of inclusion/exclusion criteria:

Inclusion                                                                                               Exclusion

  • Date range, e.g. published 2015 to present                            Date range, e.g. published before 2015
  • National context, e.g. UK only                                                   National context, e.g. non-UK
  • Age group, e.g. children, adolescents, etc.                              Age group, e.g. adults
  • Study type, e.g. Randomised Control Trials (RCTs) only        Study type, e.g. all non-RCT studies

You should provide clear justification for your choices. For example, rather than selecting an arbitrary date for inclusion (such as the last 5 years) you may want to select studies published after there has been a change in national policy or guidance.

See the University of York's Centre for Reviews and Dissemination guidance on the review protocol for further information on this. JBI have also made available this talk by Professor Kay Cooper from The Scottish Centre for Evidence-based Multi-professional Practice at Robert Gordon University on pre-planning and protocol development for systematic reviews: pitfalls to avoid and tips for success:

Registering your systematic review with PROSPERO

PROSPERO is an international database of prospectively registered systematic reviews in health and social care, welfare, public health, education, crime, justice, and international development, where there is a health related outcome.  

Key features from the review protocol are recorded and maintained as a permanent record. PROSPERO aims to provide a comprehensive listing of systematic reviews registered at inception to help avoid duplication and reduce opportunity for reporting bias by enabling comparison of the completed review with what was planned in the protocol.

See the PROSPERO registration form template (PDF link) for useful guidance and the University of York's Guidance notes for registering a systematic review protocol with PROSPERO (PDF link)

However, if you are undertaking a mini-review, a scoping review or a systematic review as part of a training exercise, please do not register your review with PROSPERO.