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Clinical Trials: Search Tips

Search Tips

Searching a clinical trials database can be challenging. Some databases have better search capabilities than others, and many have different requirements for building a proper search. Here we’ll explain how to construct effective searches for two core clinical trials resources: and the World Health Organization’s International Clinical Trials Registry Platform (WHO ICTRP). If you are using a different clinical trials database, look for a help guide on their website or ask a librarian for assistance.

You can search by using the simple search or the advanced search.

Simple Search

The simple search offers 4 different search fields: recruitment status, condition or disease, other terms, and country. All fields are optional. recommends using the “condition or disease” field to enter in keywords, such as diabetes. As you type your keywords, a list of recommended terms are shown. If you would like to narrow your results, you may enter in addition terms in the “other terms” field, such as a drug name.

NOTE: One thing to keep in mind is that searches in the “condition or disease” field tends to bring back fewer results than in the “other terms” field.

If you would like to bring results back that contain a certain phrase, use quotation marks to tell the database to retrieve results with the terms in that order.

  • For example: "pain management"


Searches can also utilize AND, OR, and NOT to connect terms together to build a more comprehensive search strategy. When using AND and OR in your search strategy, make sure to separate the terms connected with OR from AND by using parenthesis.

  • For example: (cancer OR neoplasms) AND immunotherapy


When using a longer, more complicated search strategy, it is recommended to use the “other terms” field to get the broadest range of results.

Advanced Search

The advanced search includes the same search fields as the simple search, but also allows users to select filters to apply to their results right away. Here are some example filters available from the advanced search page:

  • Recruitment status: filter studies by their recruitment status (recruiting, suspended, completed, etc.)
  • Eligibility criteria: can narrow results to sex and age groups
  • Targeted search: can use search terms to find specific interventions, study sponsors, study ID, and more
  • Additional criteria: can limit results by clinical trial phase, funder type, and study start date, among others

The filter options from the advanced search are also available on the results page after running a simple search (see below).




WHO ICTRP Search Rules

The WHO ICTRP database follows specific rules when constructing a standard search or an advanced search:

  • Do not enclose phrases in double quotes (e.g., “pain management”). Two or more words in consecutive order will be searched as a phrase.
  • Searches automatically include synonyms.
  • Use the asterisk (*) to truncate search terms (e.g., walk* will return walk, walks, walking, walked…)
    • Truncation disables automatic synonym searching.
  • Can combine terms with AND, OR, and NOT (boolean operators).
    • Do not use parenthesis to separate boolean operators. Booleans are applied in the following order of operations: NOT, AND, OR.

Standard Search



The standard search allows you to enter one or more terms. You also have the option to turn off automatic synonym searching and limit your results to specific clinical trial phases.

Based upon WHO ICTRP’s search rules (see above), your search query will look differently from searches conducted in other major databases. Here is what a typical search might look like in PubMed when combining terms with different boolean operators (AND, OR, NOT):

  • (cancer OR neoplasms) AND immunotherapy


Here is how the search query above would be translated for WHO ICTRP:

  • cancer AND immunotherapy OR neoplasms AND immunotherapy

Advanced Search



The advanced search interface allows you to search specific fields in a clinical trials record. You may leave one or more blank.

  • Title (title of study)
  • Condition (disease or problem studied)
  • Intervention (treatment or action studied)


You may also apply filters on the advanced search page as well:

  • Recruitment status
  • Sponsor
  • Secondary ID (trial registration number or other type of identification number)
  • Country
  • Date
  • Phases

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