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Structured searching for health students (using CINAHL and other databases)

Planning your search

notepad and pencil                

Planning your search

This section of the guide will cover:

  • An introduction to Boolean operators
  • An introduction to PICO/PIO
  • Guidance on planning your search using Boolean operators and PICO/PIO
  • Using PICO/PIO/PEO in a Scenario     

What are Boolean operators?

If you are unsure what Boolean operators are, this video (from LTHTR Blended Learning) covers the basics. 

Video Guide:

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The Using operators in your search tutorial, from The University Manchester, goes through Boolean operators in more detail, with examples and activities to test your knowledge. 

Online Tutorial:

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For more information on how to use Boolean operators in CINAHL see the Searching CINAHL page.


For Evidence Based Practice (EBP) searches, you will often be expected to break down your question into its key concepts using an EBP formula such as PICO, PIO and PEO. If you are unsure what PICO/PIO/PEO is, this written guide explains it in more detail and includes some example questions, question structures and search strategies.

Written Guidance
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The Creating a PICO Scenario tutorial, from The University of York, also explains the PICO formula and has some examples and activities to test your knowledge.

Online Tutorial

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Planning your search using Boolean operators and PICO/PIO

It is important to plan a search strategy before beginning your research. This will help you decide what you want to find and will save you time in the future. The written guidance and video tutorial below explain how to do this in a structured way.

Written Guidance Video Tutorial  
Picture of a note pad and pencil video camera


Using PICO/PIO/PEO in a Scenario

The Scenario

As part of the standard childhood immunisation schedule, Sarah has been asked to bring her 13 month old daughter into her local doctor's surgery for the MMR (Measles, Mumps and Rubella) vaccination. Sarah has carried out some online research about the MMR vaccine and is worried that it can lead to an increased risk of autism. During her consultation with the GP, she asks why her healthy child should be put at risk, especially as “measles is a minor illness." 

Main concepts

After reading the scenario which of the following do you think are the main keywords or concepts? Which are the ones you would choose when searching in an online database? Click the boxes to see what we thought.

Sarah: We did not think this was a key concept. Sarah is the name of the parent in this scenario. Although she is important, her name is not one of the key concepts for a literature search. You would not search usually for people's names as part of your literature search.
13 month old child: We thought this was a key concept. The 13 month old child is the main focus in this scenario.
All vaccines: We did not think this was a key concept. All vaccines would not be a useful term to search for in this scenario as it is not about all immunisations.
Autism: We did think this was a key concept. Autism is central to this scenario as it is the main concern which is being investigated.
Minor Illness: We did not think this was a key concept. Minor illness is not an important part of the search strategy. It is how the parent views measles but is not associated with the problem she would like to research.
Consultation: We did not think this was a key concept. Consultation is mentioned in the scenario but would not be the focus of any further research into the topic being discussed.
All children: We did not think this was a key concept. All children would be too broad for this topic as the focus is on how the vaccine affects a 13 month old child.
MMR vaccine: We did think this was a key concept. The MMR vaccine is one of the main concepts for this search as we want to investigate this particular vaccine.


Having looked at the keywords in the scenario we have decided it is a PIO question. There is a patient/population/problem, intervention and outcome but no comparison.
The MMR vaccine is the intervention.
In this example, there is no comparison, or you could say the comparison is not giving the vaccine.
In this example, the outcome is autism.

The question

So far we have identified the key concepts from the scenario, which framework it fits into and which components fit where. Next we need to put it into a research or clinical question. What do you think you could use for this scenario? See the written guidance and read our example below.

Does having the MMR vaccine increase the risk of developing autism in a 13 month old child?

Using material on this page