Search for the Best Evidence

Evidence-based Practice


Finding the best research evidence begins with formulating a clinical question in a systematic way. 

Using the PICOT format helps to identify keywords that, when entered successfully and then combined, expedite the location of relevant articles in massive research databases such as MEDLINE or CINAHL.

To begin your search for research evidence, it is important to choose the right terminology.

Medical Subject Headings

Medical Subject Headings (MeSH) is the National Library of Medicine's controlled vocabulary thesaurus used for indexing articles in PubMed. 

Using Medical Subject Headings provides a consistent way to retrieve information where several different terms may be used for the same concept. 

Many terms, especially drug names, are "mapped" to the MeSH.  For example:

               prozac maps you to fluoxetine

               co-enzyme Q10
  maps you to Ubiquinone/analogs and derivatives

               allergy maps you to hypersensitivity

Medical Subject Headings Logo   To connect to the U.S. National Library of Medicine

Tutorial on how to use MeSH

Connecting Terms together with Boolean Operators

Using the PICOT format to come up with search terms then requires that you combine them into a search query.
Boolean Operators allow you to narrow or broaden your search.  Let's say your clinical question concerns the effects of atherosclerosis on heart disease.

Boolean Operators:  AND   OR 

Using the Boolean Operator "OR" will give you the broadest searching capability. 

For example: 

Heart disease OR atherosclerosis will retrieve all articles on heart disease and all articles on atherosclerosis.

Image of diseased heart             Diagram of Artherosclerosis 


Using the Boolean Operator  "AND" will help to narrow your search

For example:

Heart disease AND atherosclerosis will retrieve only those articles with both search terms "Heart Disease" and "atherosclerosis".


Heart and atherosclerosis

 This method narrows the results to articles pertinent to your clinical question. 

Boolean Operators help to set limits on the final search.  If you retrieve studies in languages other than English, you can limit your search to "English" to eliminate articles in foreign languages.  In this case, your search (query statement) would be:

Heart disease AND atherosclerosis AND English

If you are searching for a topic and wish to limit the results to "human subjects", you can add the words "human subjects" to your search query.

Where to look for Evidence-based Clinical Studies and Articles

Databases provided to the public free of charge by the American Government, as well as commercial databases like CINAHL contain a rich supply of articles.  Below you will find links to these fine sources.  Librarians at NVC are available to help you, should you have difficulty locating what you need. -  Clinical Trials is a registry and results database of publically and privately supported clinical studies of human participants conducted around the world. currently lists 143,583 studies with locations in all 50 states and in 184 countries. 

MedlinePlus is the National Institutes of Health's Web site for patients and their families and friends. "Produced by the National Library of Medicine, it brings you information about diseases, conditions, and wellness issues in language you can understand. MedlinePlus offers reliable, up-to-date health information, anytime, anywhere, for free.  You can use MedlinePlus to learn about the latest treatments, look up information on a drug or supplement, find out the meanings of words, or view medical videos or illustrations. You can also get links to the latest medical research on your topic or find out about clinical trials on a disease or condition."

National Guideline Clearinghouse - The NGC is a resource for evidence-based clinical practice guidelines for treatments and interventions for hundreds of diseases and conditions.

PubMed/Medline  -  PubMed contains more than 22 million citations for biomedical literature from Medline, life science journals and online books.  While PubMed does not include the full text of journal articles, it is possible to click the icon in the top right corner of the abstract display to link to the full text, if available from Medline or from the publishers.  Check with an NVC librarian to secure a free copy of an article.

TOXNET is a database on toxicology, hazardous chemicals, environmental health, and toxic releases.  It is brought to you by the United States National Library of Medicine.

Subscription Databases through Napa Valley College Library

The following databases are brought to you by Napa Valley College through a subscription service.  You can access them here or through the library's database page.  If you are searching from home, be sure to go to the library database page for user name and password information.

CINAHL Plus with Full Text  -  This comprehensive research database provides full text for hundreds of nursing and allied health journals indexed in the CINAHL database, and includes a higher number of records, additional journals, records dating back to 1937 and expanded content. Additional materials included in CINAHL Plus with Full Text  include Evidence-Based Care Sheets and Quick Lessons which provide concise overviews of diseases and conditions and outline the most effective treatment options.  

Consumer Health Complete (Ebsco)  - Consumer Health Complete is a comprehensive resource for consumer-oriented health content. It is designed to support patients' information needs and foster an overall understanding of health-related topics. Consumer Health Complete provides content covering all areas of health and wellness from mainstream medicine to the many perspectives of complementary, holistic and integrated medicine. In addition, Consumer Health Complete includes the Clinical Reference System and the Lexi-PAL Drug Guide, which provides access to up-to-date, concise and clinically relevant drug monographs. The database is updated on a weekly basis.

Health Source-Consumer Edition (Ebsco) This resource provides access to nearly 300 full text, consumer health periodicals, and many others. In addition to full text, indexing and abstracts are provided for more than 300 periodicals. Also included in this database is searchable full text for nearly 1,100 health-related pamphlets; 146 health reference books, including books published by the People's Medical Society; 4,500 Clinical Reference Systems reports (in English and Spanish); and Stedman's Medical Dictionary, which provides users with access to terminology of genetics, oncology, pediatrics, pulmonology, emergency medicine, bacteriology, and laboratory medicine. In addition, this database includes Clinical Pharmacology, which provides access to up-to-date, concise and clinically relevant drug monographs for all U.S. prescription drugs, hard-to-find herbal and nutritional supplements, over-the-counter products and new drugs. This full text database covers topics such as AIDS, cancer, diabetes, drugs & alcohol, aging, fitness, nutrition & dietetics, children's health, women's health, etc. Many full text titles are available in native (searchable) PDF, or scanned-in-color. Full text information in this database dates as far back as 1985.
Health Source: Nursing/Academic Edition (Ebsco) - Health Source: Nursing/Academic Edition provides more than 550 scholarly full text journals, including more than 450 peer-reviewed journals focusing on many medical disciplines. Also featured are abstracts and indexing for more than 800 journals. Coverage of nursing and allied health is particularly strong and many more. In addition, this database includes Clinical Pharmacology, which provides access to up-to-date, concise and clinically relevant drug monographs for all U.S. prescription drugs, hard-to-find herbal and nutritional supplements, over-the-counter products and new drugs. The majority of full text titles are available in native (searchable) PDF, or scanned-in-color. Full text information in this database dates as far back as 1975.

MEDLINE (Ebsco) - MEDLINE provides authoritative medical information on medicine, nursing, dentistry, veterinary medicine, the health care system, pre-clinical sciences, and much more. Created by the National Library of Medicine, MEDLINE uses MeSH (Medical Subject Headings) indexing with tree numbers, tree hierarchy and explosion capabilities to search abstracts from over 4,600 current biomedical journals. Included are citations from Index Medicus, International Nursing Index, Index to Dental Literature, PREMEDLINE, AIDSLINE, BIOETHICSLINE, and HealthSTAR.


Images from the History of Medicine provides access to thousands of prints and photographs of the History of Medicine Division (HDM) of the U.S. National Library of Medicine.

Evidenced Based Medicine Information Literacy Modules
Unit 1:  What is Evidence-Based Practice?
Unit 2:  Ask Clinical Questions in PICOT Format
Unit 3:  Search for the Best Evidence
Unit 4:  Critically Appraise the Evidence
Unit 5:  Integrate the Evidence with Clinical Expertise & Patient
             Preferences and Values
Unit 6:  Evaluate the Outcomes of the Practice Decisions or
             Changes based on the Evidence
Unit 7:  Disseminate EBP Results

copyright 2014 Napa Valley College                                      Updated August 18, 2014 
                                                                                              by Nancy McEnery, Reference Librarian-Instructor