Electronic searching for trial reports in some databases may not retrieve all relevant available studies. Reports may either be missing from the database or may not have been indexed adequately due to lack of detail in titles and abstracts. Some reports are only ever published as abstracts in conference proceedings books.

Handsearching is the task of searching through medical journals (these days both hard copy and electronic copy) or conference abstract books for reports of controlled trials which are not indexed in the major electronic databases like MEDLINE and Embase. For complete identification of reports of trials, electronic searching may need to be supplemented by conducting page by page (either by use of the paper copy or electronic version) searches of a variety of sources including journals and supplements, conference proceedings and abstracts, correspondence, internet sources.