This section highlights some of the issues to consider when designing search strategies, but does not adequately address the many complexities in this area. It is in particular in this aspect of searching for studies that the skills of a Trials Search Co-ordinator or healthcare librarian are highly recommended. Many of the issues highlighted below relate to both the methodological aspect of the search (such as identifying reports of randomized trials) and the subject of the search. For a search to be robust both aspects require equal attention to be sure that relevant records are not missed.
The eligibility criteria for studies to be included in the review will inform how the search is conducted (see Chapter 5). The eligibility criteria will specify the types of designs, types of participants, types of intervention (experimental and comparator) and, in some cases, the types of outcomes to be addressed. Issues to consider in planning a search include the following:
whether the review is limited to randomized trials or whether other study designs will be included (see also Chapter 13);
the requirement to identify adverse effects data (see also Chapter 14);
the nature of the intervention(s) being assessed;
any geographic considerations such as the need to search the Chinese literature for studies in Chinese herbal medicine;
the time period when any evaluations of these interventions may have taken place; and
whether data from unpublished studies are to be included.