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Evidence Based Medicine

This guide is designed to assist health care professionals and students become effective and efficient users of the medical literature.

Upcoming Revision

The Evidence Based Medicine Guide will be undergoing a major update on Tuesday May 31st. 
We ask for your patience as parts of the guide may be unusable at various times throughout the day.

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EBM Pyramid

MEDLINE is produced by the National Library of Medicine and is the premiere biomedical database. 

  • Coverage: generally 1947 to the present, with some older material.
  • Indexes 5,400+ international biomedical journals.
  • Includes primarily journal articles, reviews, letters, editorials, comments.
  • Does include some books from NCBI's Bookshelf.
  • Abstracts are available for most entries.
  • Different platforms are available from the National Library of Medicine, commercial vendors, and universities.
  • Free MEDLINE access is available through NLM's PubMed.

Medical Subject Headings (MeSH)

MeSH Logo image


MeSH is the National Library of Medicine's controlled vocabulary thesaurus. It consists of sets of terms naming descriptors in a hierarchical structure that permits searching at various levels of specificity.  An advantage of controlled vocabularies, like MeSH, is that a single term has been used to represent a particular concept no matter how it was referred to in the original article.

  • MEDLINE uses MeSH for indexing database articles.
  • 6-15 subject headings are assigned per article, with up to 3 assigned for major emphasis of the article.
  • MeSH is updated annually to reflect current terminology usage.
  • MeSH allows for more precise subject searching. Articles are indexed to the most specific term available.
  • Using MeSH to search MEDLINE allows the searcher to apply subheadings, limits, add major emphasis, and "explode".
  • MEDLINE allows users to expand a category of terms from the MeSH TREES (MeSH terms in a hierarchy from general to specific) to retrieve all of the articles on the general term and all of the specific terms listed underneath. Terms are automatically expanded in PubMed unless you change the default.  For Example:
    Cohort Studies would include:  Longitudinal Studies, Follow-up Studies, and Prospective Studies
    Longitudinal Studies would include: Follow-up Studies and Prospective Studies
  • MeSH definitions, history, and TREES can be found in the MeSH Database at
  • Subheadings are terms which cover general, frequently discussed aspects of a subject (e.g. diagnosis, etiology, surgery, therapy). Subheadings are combined with MeSH terms to indicate a specific focus. (Example: ASPIRIN/adverse effects)
  • Limits are descriptors used for commonly occurring concepts (e.g., human, animal, female, male, infant, child, adult, aged).
  • Publication Type is a modifier available for publication types such as Randomized Controlled Trial, Meta-Analysis, and Review.

** Note: Publication Type [PT] is always singular (Practice Guideline) while MeSH terms are always plural (Practice Guidelines). [PT] indicates the report in the article is a Practice Guideline. An article which has been indexed with the MeSH term Practice Guidelines is an article about this methodology or process. Some searchers, in order to be as comprehensive as possible, will use the strategy: Practice Guideline [PT] OR Practice Guidelines [MeSH].

MeSH tutorials are available from the MeSH web page at

Building and Refining Your MEDLINE Searches

Sample MEDLINE Searches

These sample MEDLINE searches will give you practice using MeSH, applying clinical filters, and putting limits on your search retrieval. Be aware that different MEDLINE search systems have unique functions and commands.

Sample Search on Therapy

What is the evidence for the use of antibiotics for treating otitis media in children?

#1 Otitis Media[MeSH] Explode the MeSH term Otitis Media to include all types. (PubMed explodes automatically).
Drug Therapy [sh] Add the subheading Drug Therapy to focus in on this specific aspect of the subject.
#2 Anti-Bacterial Agents [MeSH] Explode the MeSH term Anti-Bacterial Agents.
#1 AND #2 Combine terms with AND to retrieve articles dealing with both subjects.  (We found over 1,500.)
Randomized Controlled Trial [pt] Using the Limits feature select Randomized Controlled Trial as the Type of Article for clinically relevant studies.
All Child: 0-18 years Limit the search to the specific age group concerned.
English Limit the search to English if you wish to eliminate foreign language articles.  (We now have about 90 citations in our results list.)
Clinical Queries Copy your search into PubMed's Clinical Queries feature and see how many systematic Reviews are found.  Or simply choose Systematic Reviews from the Subsets in the Limits feature.

Sample Search on Diagnosis

Are there any evidence based articles on the differential diagnosis of Alzheimer's Disease?

#1 Alzheimer Disease [majr] Limit the MeSH term to Major focus.
#2 Sensitivity and Specificity [MeSH] Explode the MeSH term to include more specific terms such as Predictive Value of Tests.
#3 Differential Diagnosis [MeSH] Differential Diagnosis is a useful MeSH term with closely related diseases.
#1 AND #2 AND #3 Combine terms with AND.
Clinical Trials [PT] Limit using Clinical Trial as Type of Article.

Sample Search on Prognosis

What is the prognosis for a successful pregnancy in a young woman with Systemic Lupus Erythamatosus?

#1 Lupus Erythematosus, Systemic [majr] Limit the MeSH term to Major Focus.
#2 Pregnancy [MeSH] OR Pregnancy Outcome [MeSH] OR related terms.
#3 Cohort Studies [MeSH] Select Cohort Studies for a Prognosis Search.
#4 Prognosis [MeSH] The MeSH term Prognosis is effective in this search.
(#1 AND #2) AND (#3 OR #4) Combine search history terms with AND and OR. "Nest" combined terms with parentheses.
Published in the Last: 3 years Limit the search to recent articles.

Sample Search on Clinical Prediction Guides

Are there any evidence based practice guidelines on the use of mammography in screening for breast cancer?

#1 Breast Neoplasms [majr] EXPLODE the MeSH term Breast Neoplasms and Limit to Major Focus.
#2 Mammography [majr] EXPLODE the MeSH term Mammography and Limit to Major Focus.
#1 AND #2 Combine terms with AND to retrieve articles dealing with both concepts.
Practice Guideline[pt] OR Guideline[pt] OR Consensus Development Conference[pt] Limit the search to these publication types to find published evidence/consensus on this practice.
Change Databases and Rerun Search Check other databases such as The Cochrane Library or the National Guideline Clearinghouse ( to find published guidelines.

Sample Search on Etiology

Does hormone replacement therapy increase the risk for pulmonary embolism in postmenopausal women?

#1 Pulmonary Embolism [majr] Limit the MeSH term to Major Focus.
etiology [sh] OR epidemiology [sh] Attach subheadings useful in etiology questions.
#2 Hormone Replacement Therapy [MeSH] Explode Hormone Replacement Therapy, which includes Estrogen Replacement Therapy.
#1 AND #2 AND combines these concepts.


PubMed Logo

Useful Terms for EBM MEDLINE Searching

Medical Subject Headings:

  • Clinical Trials
  • Confidence Intervals
  • Cost-Benefit Analysis
  • Decision Making
  • Decision Trees
  • Diagnosis
  • Guidelines
  • Odds Ratio
  • Outcome Assessment
  • Practice Guidelines
  • Predictive Value of Tests
  • Probability
  • Prospective Studies
  • Sensitivity and Specificity
  • Survival Analysis
  • Treatment Outcome

Publication Types:

  • Clinical Trial
  • Consensus Development Report
  • Controlled Clinical Trial
  • Guideline
  • Meta-Analysis
  • Multicenter Study
  • Practice Guideline
  • Randomized Controlled Trial
  • Review


  • adverse effects
  • diagnosis
  • drug therapy
  • etiology
  • mortality
  • prevention and control
  • therapeutic use
  • therapy

Getting Too Much With Your PubMed Search?

Try these techniques for limiting your results:

  • Use AND with another concept
  • Limit to English
  • Limit by Age, Sex, Human
  • Limit to Publication Type (for example: Randomized Controlled Trial or Review)
  • Use Subheadings (for example: Diagnosis or Therapy)
  • Use a more specific term (Femoral Neck Fractures instead of Hip Fractures)
  • Restrict to Major MeSH Topic
  • Choose "Do not include MeSH terms found below this term in the MeSH hierarchy"
  • Use Text Word in Title
  • Limit to Subsets (e.g., Core Clinical Journals)

Not Getting Enough With Your PubMed Search?

Try these techniques for increasing your results:

  • Use OR with synonymous/related concepts
  • Include all languages (English abstracts are often available)
  • Remove all Limits
  • Do not restrict to Publication Types
  • Choose All Subheadings
  • Use a broader term (Eye Diseases instead of Retinal Diseases)
  • Do not Restrict to Major MeSH Topic
  • Do not choose "Do not include MeSH terms found below this term in the MeSH hierarchy"
  • Truncate text words (recommend*)
  • Use the "See Related" feature in PubMed

Contact Us

This guide has been created by the University of Illinois at Chicago's Library of the Health Sciences at Peoria. 
Please feel free to contact us with any questions at