Searching effectively for the evidence

1. Identifying search terms

Watch the introductory Prezi below.

• Click on Start Prezi
• Click on the fullscreen icon in the bottom right corner of the Prezi window to view full screen

• Navigate through the Prezi by clicking on the arrows at the bottom of the Prezi window, or use the right and left arrows on your keyboard
• The Prezi has audio, so make sure you have sound enabled

Go to the next page to find out more about identifying search terms

1.1. Keywords (part 1)

It's really important to think carefully about keywords before you start searching.  Different authors can use a variety of terms to talk about the same thing, so it's important to identify all the relevant vocabulary.

Have a look at the photo below ...

Think of four words which you would use to describe the picture. 

Put your answers on a post-it and post them on this board and then have a look at some of the other responses.

1.2. Keywords (part 2)

You'll probably notice that there is a large variety in the words people have chosen to describe the picture:

• Specific words e.g. names of specific plants
• Broad descriptions e.g. plants, flowers, garden
• Things that are in the picture, e.g. fence, plant pots
• Words that tell you about the picture e.g. natural, bright

These words are all describing the same picture, and in the same way research on the same topic could be descibed in a number of different ways.  When you do a search, you need to make sure that you find all the relevant evidence by thinking carefully about the terminology that might have been used.  Take dental caries as an example.  Any of the following terminology could have been used:

• caries
• tooth decay
• dental decay
• cavities

If you searched just for caries, you might miss out on research that talks about tooth decay.

1.3. Generating search terms (part 1)

Always break your question down into its key components.  These will normally be determined by your PICO question. 

Imagine the following scenario:

Use this template to create a PICO question and generate some search terms for each component of your question.  Note that it's not always necessary to include all elements of your PICO in your search.

1.4. Generating search terms (part 2)

This is an example of what your search terms might be.

There's no right or wrong answers here and you may have come up with different or better terms.  For example, for the fluoride compnent of your search you may have chosen to include specific fluoride treatments, or you might just want to search for fluoride in general.  Once you actually start searching you might want to change some of your search terms.  For example, if you don't find much concerning primary teeth you might choose to just search for children, or perhaps remove that component from your search all together.

2. Searching techniques

There are a number of techniques that it's worth knowing about in order to get the best out of your search. 

Watch the Prezi below for a brief introduction.

Go to the next page to find out more about useful searching techniques

2.1. Truncation and phrase searching (part 1)

Watch this short cartoon explaining the principles of phrase searching and truncation.

Click on the icon on the bottom right of the Powtoon screen to watch full screen

Have a go at this activity to see how using truncation and phrase searching can make a difference to your search.

2.2. Truncation and phrase searching (part 2)

Here are the answers to the searching activity

You can see that using truncation gives you the largest number of results. Phrase searching narrows down your search, but can also result in missing out on some useful evidence. You'll notice that record 3) was not retrieved by any of the searches, despite being relevant. This is because it uses the term tooth ersosion, rather than dental erosion, and shows how important it is to make sure you identify all possible terminology when searching.

2.3. Subject headings and thesaurus terms (part 1)

Many databases use subject headings or thesaurus terms.  A good example is MeSH (Medical Subject Headings), used in the Medline database. 

The activity below helps to explain how subject headings and thesaurus terms are used.

• Have a look at the example
• Click on the photo to have a go yourself
• Choose appropriate headings from the list on the left that best describe the photos
• Drag your chosen terms into the spaces on each photo

2.4. Subject headings and thesaurus terms (part 2)

In the same way as you assigned terms from a defined list to describe a number of photographs, when an article is added to a database, an expert will read the full text of the article and tag it with the terms from a defined list which best describe the article.

Some of the terms you used to tag the photos were things that you could see in the picture, like trees or cake.  Other terms, like tropics or celebration, are not things that actually appear in the picture, but tell you what the picture is about.  

Whereas keyword searching finds any articles where the search term appears in the title or abstract, searching using subject headings or thesaurus terms will retrieve any articles that are about that particular topic, whether or not that actual term is mentioned in the title or abstract.  

The abstract below is a good example.  Tooth erosion is not mentioned as a term in the title or abstract, but you'll notice that it has been indexed under the term tooth erosion.

In some databases you would need to search for subject headings or thesaurus terms separately, but PubMed makes life easy for you because, if it finds a relevant MeSH term for your keyword, it will automatically search for any articles indexed under that term, as well as any articles that mention the term in the title or abstract. 

I did a simple search for dental erosion.  The search details box shows me that it's not only searched for the term dental erosion in the title and abstract (All Fields), but it has also mapped to the MeSH heading tooth erosion, as well as searching for the term tooth erosion in the title or abstract. 

So this search would retrive any articles that mention either tooth erosion or dental erosion in the title or abstract, or any articles which are considered to be about tooth erosion.

If you search using truncation or phrase searching MeSH mapping will be disabled, so you would need to search the MeSH database separately.  See how to do this in the video below

3. Structuring your search

Once you've searched using all relevant keywords, subjects headings etc., you need to structure your search strategy in order to get out useful and relevant results.

It's always best to search for the terms separately and then combine them togther, that way it's much easier to identify any bits of your search that are perhaps bringing up irrelevant results, or maybe restricting your search too much.  You can then easily add in additional terms, or remove terms from your search as necessary.

Go to the next page to find out more about structuring your search effectively

3.1. Boolean operators (part 1)

In order to structure an effective search you will need to combine terms together using what are known as Boolean operators.

Have a look at this short cartoon, which explains in more detail how to use the Boolean operators AND and OR to structure your search strategy.

Venn diagrams are often used to explain Boolean operators.  Imagine you're looking to buy a new house.

Which diagram would represent the following scenarios?

• It would be great if you can afford a place with a garden and a garage, but if you can't then either would be good.
• The dog needs somewhere to run around safely outside, but it's important that you have somewhere to put the car too.
• You have a car, but you certainly don't have green fingers, so no point spending money on somewhere with a garden.

3.2. Boolean operators (part 2)

Which Venn diagrams did you choose to represent each of the scenarios?  Here are the answers with a bit more explanation about when you'd use each of the operators.

An OR search

• It would be great if you can afford a place with a garden and a garage, but if you can't then either would be good.

Here you want to find any houses that have either a garden, or a garage, or perhaps both.  So, you would search garage OR garden, which is represented in diagram B.

An OR search broadens your search, so you'd use OR when you're combining synonyms or related terms.  For example, if you're looking for anything on dry mouth you could search xerostomia OR dry mouth OR hyposalivation, because you want to look for studies that use any of those terms. 

An AND search

• The dog needs somewhere to run around safely outside, but it's important that you have somewhere to put the car too.

In this case you're not interested in houses that have a garden, but not a garage, or those that have a garage, but not a garden.  You only want to find those that have both a garden and a garage.  So you would search for garage AND garden, as shown in diagram A.

An AND search narrows your search.  You'd use this when you want to combine different components of your search to make sure the results are specific to you research question.  For example, if you were looking for evidence on preventing dry mouth specifically in elderly patients, you could search dry mouth AND elderly, because you want to find studies that talk about both those things.

A NOT search

• You have a car, but you certainly don't have green fingers, so no point spending money on somewhere with a garden.

Here you want to find any houses that have a garage, but you then want to exclude those that have a garden.  You could do a search for garage NOT garden, as shown in diagram C.

A NOT search can be used if you want to exclude something, thereby narrowing your search.  For example if you wanted to find some evidence on risk factors for dry mouth, but were not interested in medication as a cause, you could search dry mouth NOT medication.  Be aware that this would exclude any studies that mention medication in the title or abstract, even though the article might actually talk about lots of other causes that you were interested in.  NOT searches should be used with caution as there is a risk of missing out on useful and relevant evidence.

3.3. Building your search strategy

Let's return to our question on dental erosion.

You want to find anything about primary teeth, so you combine all the terms in the first column with OR, so primary teeth OR primary dentition OR deciduous teeth etc.  This would retrieve results that use any of those terms.  You'd then do the same with the fluoride component, and finally the tooth erosion component. 

Once you've got a set of results for each component of your search you need to narrow it down to find evidence that is specific to your question.  To do this you'd combine the results of each component using AND, in order to retrieve any articles which are about all of the aspects of your question.  So your search in a database would look something like this.

It's never a good idea to mix ORs and ANDs in the same search, because the database will not necessarily combine your terms in the way you need.  It's advisable to do all of your OR searches first and then combine each set of results with AND as in the example above.

4. Refining your search

Watch this Prezi for a short introduction on refining your search.

Go to the next page to find out more about using filters to refine your search

4.1. Filters (part 1)

Filters are a useful way to narrow your search down to make it really specific to your needs.

Try this filters activity to find out more about how filters work.

4.2. Filters (part 2)

Your filtered results would probably have looked something like this

As you can see filters allow us to easily narrow down a search to make it really specific to our needs.  You probably use filters on a regular basis, perhaps if you're shopping online or booking a holiday.  Publication type filters are particularly useful when we're talking about searching for evidence.  You want to be looking for the best type of evidence to answer your question, for example systematic reviews or randomised controlled trials for a therapy question.  You can apply the relevant filters, where available, to easily narrow down your results just to those specific types of study. 

Watch this short video on using the filters in PubMed

4.3. Filters (part 3)

Filters are not always available for all study types.  Here is a video explaining how to narrow a PubMed search to look just for cohort studies

And this one explains how to search for surveys

5. Managing your results

Once you've completed your search there are a number of things you can do with your results

All databases allow you to:

• Create an account where you can save your searches to re-run later
• Set up alerts to inform you of new results
• Email your search results to yourself, save them as a file or print them out
• Add your searches to citation management software like EndNote

Go to the next page to find out more about using citation management software

5.1. Citation management software

There are a number of software packages available to help you collect, store and manage your references.  For an introduction to using citation management software see the library's QMplus course on Referencing Information.

Queen Mary staff have access to the desktop version of EndNote.  IT Services will install the software on a QMUL PC or laptop.  Watch the library's bite-sized videos for an introduction to using EndNote.

6. Summary

You can watch the complete search skills Prezi here

This video shows a complete worked search example of finding the evidence using PubMed