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Evidence-Based Practice: Step 2: Acquire

This guide contains resources and guidance to help students learning about evidence-based practice.

Step 2: Acquire


Your next step is to find the evidence. This page will show you how to develop a search strategy to find the most relevant and highest quality information to answer your question.


Identifying keywords and subject headings

In all health databases, you can search in two ways - by using keywords or by using subject headings. A comprehensive search strategy will use both to ensure you are not missing any evidence.

Click on the tabs below to see the definitions and differences.

Keywords are terms or phrases which describe your concept.

When you enter a term, the database brings back all articles which contain that term in the record.

This means you only get what you ask for - for example if you type in 'observation' the database will only bring back articles which mention 'observation'; it won't know that you are also interested in articles which mention 'monitoring'.

As you are aiming to find ALL evidence on your topic, this means you need to think about synonyms (also known as alternative terms) for your concepts.

To come up with a shortlist of synonyms to use for each of your concepts, run some preliminary searches in PubMed or Google Scholar to see the terminology used in different articles.

Subject Headings are standardised labels the database applies to articles to group them by topic. Searching using a subject heading means you are searching by topic.

Most health databases will have a way of suggesting subject headings to you when you type in your terms - however, you can also locate them in advance.

The video below shows you how Medical Subject Headings (MeSH) works. MeSH are thesaurus of subject headings used in Medline and PubMed.

Organising your search concepts

Once you have all your search terms, try organising them into a table like the one below.

This is where mnemonics can be very useful as they help you separate these keywords and subject headings into your key concepts.





school children hand washing hand sanitiser common cold
child* hand wash* hand sanitizer cold
adolescent* washing with soap antibacterial gel viral infection
    alcohol gel


Subject Headings

Hand Disinfection

  Common Cold

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Have a look at this syntax guide to learn about all the searching shortcuts available in databases like truncation (*) and adjacency searching.



nurses caring for people with diabetes
nursing staff caregiving diabetic patients
nurs* care diabetes
Subject Headings
nurses patient care diabetes mellitus
  nursing care  

Using boolean operators

Once we have all our keywords and subject headings identified, we need to consider how we combine them. To do this, we use boolean operators.

Watch the video below to learn more about boolean operators.

Here's a quick summary of how you should combine your terms in a PICO table.

Using your search in a database

Now you are ready to start searching in some databases, have a look at these short tutorials below to get you started.


Filters (also known as limits) help focus your results. They are available in all health databases and they allow you to narrow your results using specific parameters.

Filters are very useful tools to help limit your results, however, you should only apply filters sparingly. It is very easy to apply too many and end up with zero results. Common filters to include are:

  • Publication type e.g. Randomised controlled trials
  • Language e.g. English
  • Publication date e.g. last 10 years, 2011-current

The videos below cover how to apply filters in each database.

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Some health databases will have a type of filter available called "Clinical Queries" - these are pre-made search filters that help locate a range of study types and evidence that can best answer a category of clinical question.

Examples of clinical question categories include: therapy, prognosis, diagnosis, or qualitative.

Have a look below to get an idea of what database is right for you! 

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Medline is a large medicine and health database, with extensive US coverage. 

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PubMed contains everything in Medline and covers additional topics around the life sciences, chemistry and general. The search interface is very user-friendly.

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Embase is a large medicine database with focus on drugs, medical devices and health topics. It covers a number of European journals.

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CINAHL provides authoritative coverage of the literature related to a wide variety of nursing and allied health topics.