Database search limits (also called filters) can be used to narrow the range of database records that are found during a search.
Common limits include year(s) of publication, type of study, age or sex of the subjects studied, or limiting the search to text found only in certain parts of the database records such as the title, abstract, or author names.
Different databases may have different limits available and vary in exactly how they are applied to a search.
Limits in PubMed
PubMed presents available limits as a list of "filters" on the left hand side of a search results list:
Using limits in EBM searching
Particularly useful limits to use in EBM searching are those concerned with:
Use this to limit the results to review articles, RCTs, etc.
Use these limits to narrow your results to studies that relate to your patient, e.g. middle-aged female, adolescent male.
For example, our search for information on smoking and headaches in teenagers, we can use the Age limit to narrow our results to papers concerned with adolescents rather than using several terms for teenager.
(smoking OR cigarette*) AND (headache* OR "head pain" OR "head pains" ) AND (teenag* OR adolescen* OR "young adult" OR "young adults" OR "young adulthood")
can now be written as:
(smoking OR cigarette*) AND (headache* OR "head pain" OR "head pains" )
and the limit for the adolescent age group can be applied:
Adolescent: 13-18 years
This should find papers that study subjects in the 13-18 year age group regardless of the terminology used by the author (teenager, adolescent, etc.).
1. Several limits can be applied to a given search, but applying too many may narrow your search too much, perhaps even producing 0 results.
2. Several categories can be applied within in each limit if a single category doesn't apply, e.g. you can choose Adolescent: 13-18 years as well as Young Adult: 19-24 years.
See the link below demonstrating the use of limits in PubMed: