Litteratursøk

Abstract

In this article we describe the basic principles on how to perform systematic searches for research literature. A well-conducted literature search is based on a clearly formulated question, expressing what one is looking for. Questions regarding effects of interventions can be structured with the aid of PICO, stating the population, intervention and outcomes of interest. The first step is to identify English search terms that describe the different PICO categories. It is important to search for all relevant synonyms and spellings in order to identify as many relevant studies as possible. One may also search for standardized subject headings that are used to describe the content of the publications. Search terms are then combined with the Boolean operators AND and OR. In order to end up with a reasonable amount of references, one can limit the search to specific publication years, age groups and relevant study designs. To ease the process of scanning through the search hits, it is advisable to export the search results into reference management software, such as Reference Manager or Endnote. Many databases also allow saving the searches for use at a later stage. Sometimes it might be necessary to use supplementary search methods, such as searching trials registers, scanning through reference lists of relevant publications, conducting citation searches, and contacting content experts to identify further relevant studies. The search process, including the selected sources and search terms, should be documented and reported. Even though advanced systematic searches often are performed by librarians, everyone can learn how to search for literature. It is a "learning by doing" process, and we recommend contacting a librarian for further guidance and help.