Skip to Main Content

Evidence-Based Practice PT

Keyword Searching

 Keyword searching:

Running a keyword search returns documents that include or mention the term you searched for. 

For example imagine you ran this search on Parkinson's disease

CINAHL Search Bar Example for the search, parkinson's disease

The search results would include either:

  • Articles that are about Parkinson's disease
  • Articles that mention Parkinson's disease
  • Articles that are that about a separate topic, but occasionally mentions Parkinson's disease

Essentially a keyword search searches for words, not topics, which increases your chances of missing an important article that is about your topic.

One key strategy in making sure you find more precise and relevant articles based on your topic is understanding that most terminology with have alternate spellings and synonyms. Your search will expand if you can find ways to use alternate words to describe your topic. Additional terms for Parkinson's disease we can use include:

  • Parkinson disease
  • Parkinsons disease
  • Parkinsons
  • Parkinsonism
  • People with Parkinson
  • pd

Controlled Vocabulary

Keyword searching can be restrictive on how many results you get when you are conducting a literature search.  Therefore many scholars who need to do a thorough literature search on a topic use controlled vocabulary.  Controlled vocabularies group synonymous words under one main term: a Subject Heading. Conducting a search using Subject headings means researches find articles that are about their topic, rather than just mentioning the topic.

Examples of keywords and subject headings in PubMed and CINAHL

Keyword MeSH (PubMed) CINAHL Headings
heart attack myocardial infarction myocardial infarction
surgery general surgery surgery, operative
hand washing hand disinfection hand washing
physical therapy physical therapy modalities  physical therapy

Boolean Terms

What is Boolean Logic?

Boolean logic defines logical relationships between terms in a search.  The boolean search operators are AND, OR, NOT. Enter these terms in ALL CAPS in the databases because many search engines, although not all, are case sensitive for these concepts.


By using AND in your literature search, you are telling the database to bring back search results in which both search terms occur.

For example, if you are running a searching for "gait training for Parkinson disease" you may want to write it out as "gait training AND Parkinson Disease".  The search engine will recognize that you are looking for both concepts together.

Venn diagram of the boolean concept of AND. example of gait training AND parkinson's disease


By using OR, you are having the database search for either of the items you are looking for.  This broadens your search results.

For example, if you run a search for "gait training AND Parkinson disease" you will potentially miss out on articles that deal with "gait rehabilitation".  However, using OR you can run a search that uses both concepts.  For example, "(gait training OR gait rehabilitation) AND Parkinson disease".  Running a search with OR increases your search results, but also increases your chances of finding more relevant articles

Venn diagram of the boolean concept of OR. example of gait training OR gait rehabilitation

Inclusion and Exclusion Criteria

Your search strategy must describe the appropriate inclusion criteria and exclusion criteria.

The inclusion criteria must be as “inclusive as possible” as it is the first step to select the evidence you want to collect to answer your foreground question. The inclusion criteria MUST clearly relate to the foreground (PICO or related) question and include most of the components of the PICO (or related) question. For instance, the population/problem and the intervention/indicator you want to study. Other inclusion criteria may involve the highest levels of evidence (synthesized and non-synthesized) that you want to include to answer the foreground question. However, remember as you want to start being “inclusive” you might change the level of evidence to be included based on preliminary results. For instance, if you could not find Randomized Controlled Trial you may consider other quasi-experimental study designs.

The exclusion criteria is an active process that is NOT limited to the non-inclusion criteria but rather reflect reasons to exclude at each step of the literature search process. For instance, you may exclude a study because it is not assessing the outcomes of your foreground question, or is not using a comparative group (control group, placebo group, pre-test or another intervention), or it does not assess the population in the setting of interest. It is important to consider that exclusion happens after the inclusion and continues until the final process of selection of the evidence to appraise. In many cases, you exclude even after you have read an article of interest. Try to avoid excluding by “title” of the article as you may miss the opportunity to include important evidence. Remember the exclusion process might happened as early as in the process of reading the abstract or later during the process of screening the article.

Creating an Automatic Search