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Medical Sciences: Search skills for systematic reviews: Selecting and searching databases

This tutorial will guide you through the steps required to systematically search for your research projects.

To undertake an extensive search and explore your research question fully you should expect to search a number of different databases. Each database covers a different range of sources, content (some are subject specific, others more general) and time frames. The databases you select to search will be influenced by your research question and its focus. You may search interdisciplinary databases such as Web of Science and Scopus, or a subject specific database such as Embase. You can explore all the subject specific resources available to you via the Medical Sciences A - Z Database listing. 

Most databases contain a variety of research material, not just journal articles! Many of these other types of resources (such as book chapters, meeting, poster presentations and conference proceedings) will only provide abstract information (you will not be able to access the full text). You can use the refine / limit option to restrict your results to academic journals if you would like to exclude other types of resources. Use the support material below to learn more about the databases and how to effectively search them. 

Web of Science

Web of Science is a large multidisciplinary research database covering all subject areas.

You can use it to discover the global literature on a wide range of topics.  It is not a full text database, but you can use it to discover published material and follow links through to discover the full text available on other services. For in depth guidance explore the Web of Science learning site, YouTube Videos or the Web of Science LibGuide.

Once you click the Search button, the results page appears:

Use the limiter / filter options to help focus your results to the most relevant materials. Typical database filters include: 

  • Publication date: Limit results to those published in a relevant date range.
  • Source type: Filter results by type; e.g. academic journal, conference paper, report, thesis etc.
  • Publication title: View results from specific publication.
  • Subject: Filter results by associated subject 'tags'.

Medline Ovid, APA PsycInfo and Embase

Ovid is an advanced search platform allowing you to perform sophisticated literature searches. The Ovid platform provides access to a number of different research databases including Medline (Ovid), APA PsycInfo and Embase. 

It is good practice to search each database individually. Searching more than one database at a time will disable the thesaurus feature and is not advisable for comprehensive systematic searching.

Once you have selected the database you wish to search you will see there are a number of different types of search options available, each allows you to perform a different type of search. Using Multi-field or advanced search is recommended for systematic searches. For in depth guidance on searching Ovid explore the Searching Ovid LibGuide.

The Multi-field search option allows you to find keywords or phrases in a particular field such as author, title or abstract as well as combing concepts together to build a more complex search. You can choose the fields to search by using the drop-down menus on the right, and the combination options using the drop-down menus on the left. 

Multi-field search option

Applying limits to your search: 

Limits offer the option to refine your search according to criteria that are difficult to search using keywords – e.g. the type of article, publication date, age group, language of publication, etc. You can select one or more, click Search and your limited search will appear as an additional line in your search history. Click the Additional Limits link to view a selection of all the limits.

Once you have run your search you can apply limits to increase the relevancy of your search results. You can filter your search results using the grey bar on the left side of the screen. For example, you can limit by date or publication type.

Filter by options

Top Tip: Applying limits one at a time, this allows you to see the effect each limit has on the number of results.

Each reference will have a check for this at Exeter button, click on the link to see if the full text is available (not everything is!).

A new window will open to check if full text is available and provide a link if access is available. You may need to click on the document link (some browser pop-ups prevent automatic opening) to be directed to the full text.

SCOPUS

Access to thousands of abstracts for articles, conference papers and book chapters across a range of subject disciplines. Use SCOPUS to link to full-text holdings, find related items and track article citations.

Document search is the default option, searching for your search terms in the article, title, abstracts and keyword fields. You can add additional rows to your search query by using the plus button. Use the limit option to restrict your search results based upon date range, document type or access type. For more information about how to search SCOPUS on the LibGuide or see their range of tutorials.

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Your Search Results

  • Only search one database at a time (even if there is an option to search more)! 
  • Note down which search option you are using e.g. multi-field or advanced search, the search fields / settings can be different and this can impact on your results. 
  • As controlled vocabulary and functionality varies between the databases you may need to modify your search strategy to accommodate this. 
  • Check the databases help section to see the advanced search options available. This will help you to decide which search techniques to use. These do vary between databases!  
  • If phrase searching is too restrictive you may wish to use proximity searching instead. 
  • If you have already found or know about an article or study that perfectly matches your topic, it can be helpful to look at the terms used in their title, abstract or keywords and apply them to your own search strategy. This will help you to locate more articles like it.
  • Citation searching can be a useful way to find additional relevant studies. It involves examining reference of key studies and looking at who has subsequently cited it.

Once you have run a search, you will need to review your results and identify the relevant studies for your research question. This is often referred to as the screening process. It involves: 

  • Using the title and abstract you need to decide which articles  / studies should be included.
  • Decide what is eligible and is to be included and record the reasons why things were excluded.
  • Sometimes you need to see the full text before you can decide if something should be included or not.
  • Decide what you need to find in the full text, if you cannot decide from the title and abstract what should be included. Note reasons for exclusions.
  • You will need to critically appraise the results you have found.
  • Now you need to decide what sort of analysis you would do with the results you have found.

If your search only finds a few references, or most of the references are irrelevant to your research topic, consider the following:

  • Check your spelling: databases will not usually auto-correct, so they will only find what you type.
  • Could you add more search terms? Look for variations in spelling and alternative words.
  • Use a broader search question.
  • Do you need to search more or different databases?
  • Discuss your topic with your supervisor.

 

If you have too many results, you may have to focus your search and make it more specific. Ask yourself:

  • Have you used Boolean operators correctly? For example, have you used AND when you should have used OR?
  • Could you limit it by date range?
  • Could you limit the search by language e.g. English only?
  • Do you need a specific type of paper e.g. systematic review or random control trial? If so is there a filter option available?
  • Are you interested in a specific age group e.g. children or elderly? Some databases such as MedLine have a filter option you can use.

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