[Searching for primary studies for inclusion in systematic reviews].

Searching for relevant literature is an important process when carrying out a systematic review. Although general-purpose literature databases such as MEDLINE contain a huge number of articles, only a small fraction of these report evidence applicable to a systematic review. Development of an optimal search strategy giving priority to minimizing the number of important articles not retrieved is thus desirable. The retrieval of relevant studies cited in literature databases can be substantially enhanced by selected combinations of indexing terms and textwords. In order to improve the likelihood of retrieving studies relevant to a specific clinical question, precise database search skills are required: creation of an explicit, well formulated question using PI (E) CO, and development of a list of optimal indexing terms such as MeSH and textwords. However, even a search strategy yielding maximum sensitivity could omit some relevant articles. Consequently, hand-searching for articles in key or unindexed journals is still necessary to identify all relevant studies.