World Health Organization site
Skip Navigation Links
Home
Advanced Search
List ByExpand List By
Search Tips
UTNExpand UTN
ICTRP websiteExpand ICTRP website
Contact us
Search Tips (Please choose) 

Standard Search Tips page

Summary
  • The standard search looks for terms (words or phrases) in Title, Primary sponsor, Health Condition(s), Intervention(s), Countries of recruitment, Main ID, Secondary ID(s)
  • The standard search also looks for partial matches of Main ID (eg 17647 finds records with Main IDs such as ISRCTN01764719, NCT00517647 etc)
  • Search results are ordered by date of registration, but other orders can be chosen
  • A phrase is two or more words in succession (eg breast cancer). Do not enclose a phrase in double-quotes
  • The standard search is sensitive, finding as many records as possible
  • The standard search automatically includes synonyms for terms
  • The standard search is not case-sensitive
  • Use the asterisk (*) as a wild card for truncation (bacter* finds words such as bacterial, bacteraemia, bacteriological)
  • Combine term searches using Boolean operators:
  • OR: find any of the terms
  • AND: find all the terms
  • NOT: find the first term without the second term
Note:
  • Truncation disables synonym searching
  • Do not use truncation in the middle of a word or phrase (eg liv* cancer will not return any hits)
  • Do not use parentheses when mixing Boolean operators. Booleans are applied automatically in the following order: NOT, AND, OR.


Full description and examples

The standard search finds trial records containing particular terms (words or phrases) in any of the following fields:
  • Title (both public and scientific)
  • Primary sponsor
  • Health Condition(s) or Problem(s) studied
  • Intervention(s)
  • Countries of recruitment
  • Main ID
  • Secondary ID(s)

The standard search is sensitive, finding as many relevant records as possible. For a more targeted (specific) search you may want to use the Advanced Search

Main ID search
The standard search finds partial matches of a trial's Main ID. For example, searching for 17647 finds records with Main IDs such as ISRCTN01764719, NCT00517647 etc.

Sorting results
The default order of search results is by descending date of registration. You can change the sorting to a different field by clicking on its heading in the results table:


Clicking on the same heading again reverses the order of sorting.

Synonyms
The standard search looks for trial records containing synonyms of search words or phrases using the UMLS metathesaurus

Punctuation
The standard search strips out the following characters from your search terms: ( ) [ ] " $

Phrases
To search for a phrase simply enter the words together in the search box. You do not need to enclose them in quotation marks. So, to search for the phrase diabetic retinopathy simply enter

           diabetic retinopathy

Truncation
The standard search treats an asterisk (*) at the end of a string of letters as a wild card and looks for any word beginning with the letters already entered. So, a search for:

           bacter*

finds records with any of the words bacterial, bacteraemia, bacteriological.

Note: Truncation disables synonym searching! This means it may reduce search sensitivity. For example, a search for liver cance* may result in less hits than a search for liver cancer (which also searches for synonyms).

Truncation in phrases
It is best to avoid truncation in phrases. The search engine does not return any hits if truncation is applied to words at the beginning of a phrase. For example:

           liv* cancer

does not return any hits, but

           liver cancer

does return hits, as does

           liver cance*

Truncation of the last word in a phrase is treated as truncation of all words in the phrase, so a search for

           liv cance*

finds records containing the phrase liver cancer.

This also works for phrases composed of more than two words, so a search for

           prim bil cirrhos*

finds records containing the phrase primary biliary cirrhosis.

Combining words or phrases
Use Boolean operators to combine search terms (either words or phrases):
Operator Result Examples
OR records containing any of the search terms asthma OR eczema
finds records containing either the word asthma (or any of its synonyms) or the word eczema (or any of its synonyms), or both

asthma OR breast feeding
finds records containing either the word asthma (or any of its synonyms) or the phrase breast feeding (or any of its synonyms), or both.
AND records containing all of the search terms asthma AND eczema
only finds records that contain both the word asthma (or any of its synonyms) and the word eczema (or any of its synonyms).
NOT records containing the first term but not the second term asthma NOT eczema
only finds records containing the word asthma (or any of its synonyms) but which don't also contain the word eczema (or any of its synonyms).

Parentheses and order of precedence when using Boolean operators
The standard search is designed to be sensitive. Any number of terms can be linked using Boolean operators. However, some combination of ANDs, ORs and NOTs can lead to ambiguity. Care must be taken when constructing such a search.

Parentheses can not be used to determine the order of precedence. Boolean operators are evaluated according to the following order of precedence:
  1. NOT
  2. AND
  3. OR


Examples

Example 1

A search for:

           blood AND nutrition OR pressure

is equivalent to

           (blood AND nutrition) OR pressure

ie finds records with both blood and nutrition first and that result is combined using OR with records containing pressure. The logic also applies to synonyms of those words.




Example 2

A search for:

           blood NOT pressure OR nutrition
 

is equivalent to

           (blood NOT pressure) OR nutrition


    


To search for records with blood which don't have either pressure or nutrition — equivalent to blood NOT (pressure OR nutrition) — enter the search as:

           blood NOT pressure AND blood NOT nutrition




Example 3

A search for:

           blood NOT pressure AND nutrition

is equivalent to

           (blood NOT pressure) AND nutrition





To search for records with blood and pressure or nutrition but not both — equivalent to blood NOT (pressure AND nutrition) — enter the search as:

           blood NOT pressure OR blood NOT nutrition




For Crawlers only
Weekly updated links to all the trials.  Click here

Disclaimer: Trials posted on this search portal are not endorsed by WHO, but are provided as a service to our users. In no event shall the World Health Organization be liable for any damages arising from the use of the information linked to in this section. None of the information obtained through use of the search portal should in any way be used in clinical care without consulting a physician or licensed health professional. WHO is not responsible for the accuracy, completeness and/or use made of the content displayed for any trial record.
Copyright - World Health Organization - Version 3.2 - Version history