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How to conduct an effective and valid literature search

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A literature search is a well thought out and organised search for all of the literature published on a topic. A well-structured literature search is the most effective and efficient way to locate sound evidence on the subject you are researching. Evidence may be found in books, journals, government documents and the internet. This article describes the key principles involved in conducting a literature search.

Harvard, L. (2007) How to conduct an effective and valid literature search. This is an extended version of the article published in Nursing Times; 103: 45, 32-33.

Lori Havard BSc, MLS, is subject librarian, School of Health Science and School of Medicine, Swansea University

A literature search is a well thought out and organised search for all of the literature published on a topic. A well-structured literature search is the most effective and efficient way to locate sound evidence on the subject you are researching. Evidence may be found in books, journals, government documents and the internet.

Creating a question

Creating a well-focused question is the first step in a literature search. Having a clear idea of what you are researching will keep you on track with your searching, saving you valuable time. A focused question will give you a better start with your search because it will help you determine appropriate keywords and limitations for your topic.

When forming your question, make sure you are specific about your research topic. Things to consider are:

  • The type of patient;
  • The condition or situation you are researching;
  • The type of intervention or nursing procedure you are investigating.

This is a good time also to determine limitations to your search, such as:

  • How many years you want to go back in the literature; you may want to limit the years to make the search more manageable or clinically up to date, while capturing key information for your research.;
  • Language: are you limiting the search to sources in the English language?
  • Geographical specifity, for example, limited to the UK or EU or to include international literature.

Sources of information

Information can come from many sources, in print or electronically.

Books can be a good start on a topic, giving you general or specific information. Check that the book you are referring to is up to date – generally, this means published within the last five years – especially if you are looking for clinical or drug information.

You can find books on your area of research in an academic or healthcare library. Consult with the librarian to help you find any books that you need.

Journal articles are one of the best sources of information as they can be selected for being current and specific. Additionally, most of the important and ground-breaking research is published in journals. Journal articles are best found using citation databases, such as BNI and CINAHL.

Your search strategy can be used in all databases. Each database has some unique searching features. Your local library may hold sessions on how to search these databases or have guides to help you get started. Many databases have help screens or tutorials to help you familiarise yourself with their searching interface.

There are many types of articles and you need to be aware of the differences:

  • Research articles, including systematic reviews, are the best source of evidence;
  • Review articles give a summary of research articles on a topic;
  • Commentaries and opinion pieces can include interpretations on research or letters to the editor and editorials;
  • Case studies are a type of research that focuses on one person or situation, as opposed to a group of studies.

It is important to look for research in peer-reviewed journals. This means that the articles published have passed through peer critiquing before they are accepted for publication. This ensures that the articles have had some quality control.

Internet sources are an invaluable source of evidence. A lot of research and statistics are published on the internet, especially those sponsored by government, academic and non-for-profit agencies.

Useful information, such as clinical guidance and government policy, is available in full and is free to download.

Be extra careful in evaluating sites, as anyone can put information on the internet. There are good web portals, such as Intute ( which serve as gateways to the Internet. These portals provide links to websites that have been reviewed by subject specialists in healthcare.

The internet is an excellent source to find official publications in full. Sites such as British Official Publications Current Awareness Service / (BOPCAS), The Stationery Office ( and the Department of Health ( provide links to government documents.
The National Library for Health ( gathers guidelines, standards and various sources of evidence, as do NHS sites from home nations, for example, Health of Wales Information Service (HOWIS) ( and Scottish Health on the Web (
Statistics are an important part of research and are widely available on the internet. The Office of National Statistics ( contains a lot of information on health and social conditions in the UK.

Creating a search strategy
A search strategy is a well thought out plan to search for information. It is particularly important when using electronic citation databases, for example, CINAHL, BNI, Medline or ASSIA, as it keeps you focused on your topic and within the boundaries of what you want to search.

Key words and phrases
Your search strategy will take your research question and break it into keywords or phrases. Keywords and phrases are very important to your search. Sometimes it is best to think around a topic as much as possible to identify useful terms.

Many people find it useful to create a chart with the keywords and any synonyms you can think of or similar terms. You can also truncate your words or insert wildcards to expand your search (Box 1).

Box 1. Truncated and wildcard words

Truncate means finding the base of a word to find any words that begin with that base: Nurs* = nurse, nurses, nursing, nursery. Wildcards are symbols you use to replace one or more characters in a word: Wom?n = woman or women.

Some nursing and medical terms are spelt differently in the US and the UK, so it is best to include both spellings for these words.

Box 2 provides an example of a chart used to explore handwashing compliance by nurses.

Box 2. Example of chart for researching handwashing compliance by nurses




Hand wash*


Hand hygiene

Putting terms together

Now that you have your terms along with their synonyms, truncations and wildcards, you can start putting them together.

Boolean logic is the way to put terms together in a search by using AND, OR, NOT.

Narrows your search by making sure that all your terms show up in an article.
Example: handwash* AND complian* AND nurs* would bring back articles that relate to handwashing and compliance and nursing - including all the truncated forms of the words.

Broadens your search by allowing any of the terms to show up in an article; it is also useful for linking together synonyms.
Example: handwash* OR hand wash* OR hand hygiene would bring back articles with handwashing and its synonyms.

If you are using terms and synonyms together in a database or Internet search, you must put these in brackets.
Example: (handwash* OR hand wash* OR hand hygiene) AND (complian* OR non-complian*) AND nurs* .

Narrows your search by eliminating a term from your search.
Example: handwash* NOT alcohol gel would bring back articles on handwashing, but not articles on alcohol gels used in handwashing

Phrase searching will help you if you are looking for a specific phrase or title. You need to put the phrase in quotation marks.
Example: “NHS Code of Practice” .

Critiquing tools

Critiquing a paper or a website is an important skill. Many published papers have gone through a peer review before publication but it is always important for you to do your own critiquing to determine the quality of the article and if it is relevant to your research.

There are various tools to help you critique a paper. One is the Critical Appraisal Skills Programme (CASP) from the Public Health Resources Unit in the NHS.

Below are two checklists that you can download from CASP:

  • Qualitative research - CASP looks at ‘rigour, credibility and relevance’. Appraisal Tool.pdf
  • Quantitative research - CASP looks at the validity of the research, examines the results and if the results can be used locally to answer your research question. A number of tools are provided to critique a variety of quantitative research, such as systematic reviews, randomised controlled trials, cohort studies, case controlled and diagnostic test studies.

There are also checklists for critiquing a website. One is the DISCERN checklist (

Key points

  • A well-designed literature search will include a research question that will provide keywords and phrases to begin creating a search strategy;
  • Your search strategy will include keywords and synonyms, along with any truncation or wildcards. You will also apply limits to your search, such as language or publication years.
  • There are many resources that you can use to search for information, including print and electronic resources. All literature that you retrieve should be critically appraised in order to determine its quality and relevance to your search.
  • Librarians at local public, academic and health libraries can be a valuable source of information and support during your literature search. They can advise you on resources to search and which databases, journals and books you have access to.


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