The Literature Search
In the previous module, we learned how to construct a well-built clinical question. Using that question, we will move on to the literature search.
Constructing a well-built clinical question can lead directly to a well-built search strategy. Note that you may not use all the pieces of the well-built clinical question in your search strategy. Instead of using the term therapy, we might look for a database limit that can be used to find clinical studies involving therapy, or a publication type to find randomized clinical trials, to get at the concept of treatment. However, you may use outcomes or type of question when you review the articles for applicability to your patient.
Select a resource
The practice of Evidence-Based Practice advocates that clinicians search the primary literature to find answers to their clinical questions. There are literally millions of published reports, journal articles, correspondence and studies available to clinicians. Choosing the best resource to search is an important decision. Large databases such as CINAHL and PubMed/MEDLINE will give you access to the primary literature. Secondary resources such as ACP Journal Club, Essential Evidence, FPIN Clinical Inquiries, and Clinical Evidence, will provide you with an assessment of the original study. These are often called "pre-appraised" or EBP resources. The Cochrane Library provides access to systematic reviews which help summarize the results from a number of studies. While LSCS Libraries does not subscribe to the Cochrane Library, your hospital or physician network may.
To quickly find an answer, we might first look at an appraised resource, such as ACP Journal Club. ACP Journal Club's general purpose is to select from the biomedical literature articles that report original studies and systematic reviews that warrant immediate attention by physicians attempting to keep pace with important advances in internal medicine. These articles are summarized in value-added abstracts and commented on by clinical experts. Studies included in this small database are relevant, newsworthy and critically appraised for study methodology.
PubMed/MEDLINE is a very large database with over 17 million citations. Published by the National Library of Medicine, this database is available freely to the public as PubMed. There are advantages in using the LSCS Libraries' version, Medline.
You can search CINAHL, Medine and other databases at the same time by selecting the "Choose Databases" just above the search box. Check boxes for any database you wish to include in the search. If you include general databases, such as Academic Search Complete, make sure your keyword list includes alternative terms.
If you search MEDLINE, remember that it does not typically include the full-text of the article. Use the "Check LinkSource for More Information" link to see if another LSCS-provided database includes the full-text or if one of the LSCS Libraries makes the article available in print.
You will need your focused question and search strategy for both databases.
Conduct the search in CINAHL:Step 1: Use PICO to formulate the search strategy; start with the Patient problem and complication.
Find the terms for the patient problem: periodontal disease AND diabetes
To make sure you are using the correct terminology in CINAHL, use the CINAHL Headings link. CINAHL Headings follow the same structure as the Medical Subject Headings (MeSH) used in Medline/PubMed and the National Library of Medicine. Additional headings have been added to reflect terminology used by nursing and allied health professionals. provides a tutorial to demonstrate more about how you can construct a search from this link.
PubMed will attempt to map your terms to appropriate Medical Subject Headings (MeSH). MeSH is the standard terminology used by the indexer and helps find articles on the topic, regardless of the exact wording used by the authors.
Step 2. Look at relevant articles to verify CINAHL subject headings
The result list will display an abbreviated reference, including the publication information and the subject headings for each article. Scan for any other terms you might add to your search strategy or use to revise or focus your search.
Step 3. Limit to appropriate study design
CINAHL has added Clinical Queries as a way to limit searches to retrieve scientifically sound and clinically relevant study reports. Searches can be refined using specific search strategies designed to produce results in five research areas:
Three strategies are provided for each area:
You can also choose Clinical Trial and/or Research as a Publication Type. You will have to evaluate articles carefully to see if they fit the criteria for a Randomized Clinical Trial.
Step 4. Review the results
Both methods limit your results to RCTs. If you find a large number of studies, you can search for systematic or literature reviews.
If you would like to learn more about searching PubMed, review the PubMed tutorials at http://www.nlm.nih.gov/bsd/disted/pubmed.html. Remember that PubMed is available free to the public. Links to the full-text article from a free source or to the publisher are usually provided. If there is a fee for the article, ask your college, hospital or public library if they can obtain the article through interlibrary loan.
Revised July 2010 / Adapted February 2011