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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

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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




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