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: ClinicalTrials.gov 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 ClinicalTrials.gov by using the simple search or the advanced search.
The simple search offers 4 different search fields: recruitment status, condition or disease, other terms, and country. All fields are optional.
ClinicalTrials.gov 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.
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.
When using a longer, more complicated search strategy, it is recommended to use the “other terms” field to get the broadest range of results.
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:
The filter options from the advanced search are also available on the results page after running a simple search (see below).
The WHO ICTRP database follows specific rules when constructing a standard search or an advanced 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):
Here is how the search query above would be translated for WHO ICTRP:
The advanced search interface allows you to search specific fields in a clinical trials record. You may leave one or more blank.
You may also apply filters on the advanced search page as well:
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