Public Health: Creating a Search Strategy in PubMed

What is PubMed?

According to the National Library of Medicine, "PubMed is a service of the US National Library of Medicine® that: Provides free access to MEDLINE®, the NLM® database of indexed citations and abstracts to medical, nursing, dental, veterinary, health care, and preclinical sciences journal articles. Includes additional selected life sciences journals not in MEDLINE."

PubMed vs. Google Scholar

Google Scholar is a great tool for searching across disciplines, but searches often yield many irrelevant results. PubMed is specifically useful for searching within the biomedical sciences. You can also use a controlled vocabulary to produce highly relevant search results.

Controlled Vocabulary

In PubMed, controlled vocabulary terms are referred to as Medical Subject Headings or MeSH terms. MeSH terms allow users to narrow their searches to articles specific to those terms, rather than to articles that simply contain a keyword within the title or abstract. For example, conjunctivitis antibiotics as a keyword search yields 2,856 results, whereas "conjunctivitis"[mesh] AND "Anti-Bacterial Agents"[mesh] yields 1,251.

Keywords to MeSH Terms

Access the MeSH Database (a thesaurus) via the PubMed homepage. Input keywords and select the most appropriate MeSH term. Some keywords happen to be MeSH terms, while others map to something entirely different.

The following is an example of a research question and the process used to construct the search strategy to find literature related to answering it. This is an introductory search that does not use subheadings or discuss the MeSH tree. 

Step 1: Form a research question using the PICO format. PICO stands for Population, Intervention, Control, and Outcome.

• “How do patients with ischemic cardiomyopathy with biventricular pacemakers versus those with defibrillators fare in terms of mortality and ejection fraction?”  
  • P- Ischemic cardiomyopathy
  • I- Biventricular pacemakers
  • C- Defribrillators
  • O- Mortality and ejection fraction

Step 2: Determine which pieces of the research question are most relevant to you search. It is not uncommon to search only by the PI, or PIC components. 

Step 3: Create a concept table. Designate one row per concept, and a column each for MeSH and Keywords. 

Step 4: Brainstorm keywords related to each concept. Between each keyword, insert a capital OR. When you place OR between words, you increase the size of your search. Insert a * to truncate words. For example, patient* will retrieve every permutation of patient (e.g. patient, patients).

Step 5: Use the MeSH Database in PubMed to map keyword to MeSH terms.  Between each MeSH term, insert a capital OR. When you place OR between words. By creating a concept table, you have essentially created a search formula. Each row represents one concept, which will be coupled with the other rows: (Ischemic Cardiomyopathies) AND (Defibrillators) AND (Pacemaker). 

Step 6: In PubMed, use Advanced Search to translate the concept table into a search strategy. Designate one line per concept. Once you have created one line per concept, use the Boolean operator AND to combine each concept. See below. 

Limits

You may filter your search in a variety of ways. You can limit by article type, age, language, publication date, species, sex, and subject. To apply a limit, select the term. Note that limits appearing on the left-hand side will not be activated until selected.

Finding Similar Articles

• Browsing Similar Articles: Click the title of the article. On the right-hand side of the page, select “see all” under the Similar Articles box.
• MeSH: You may also locate similar articles by browsing articles MeSH terms. You may expand your search to include MeSH terms from similar articles.

Finding Full Text

Once you’ve identified an article you’d like to read, click the title of the article. Select either the dark green “Dartmouth Full Text” button or the light green “Get It” button. If Dartmouth licenses the journal in which the article is contained, you’ll be able to read the full text immediately. If Dartmouth does not have access to a particular journal, you may request it through Interlibrary Loan, Dartmouth’s interlibrary loan system. You may also wish to check Google Scholar.