Constructing an effective combination of search terms for searching electronic databases requires a structured approach. One approach involves breaking down the review question into ‘facets’. Several generic templates exist, e.g. PICOS (Population, Intervention, Comparator, Outcome and Study design), PIRT (Population, Index test, Reference test, Target disorder), SPICE, ECLIPSE, SPIDER, etc. (See Appendices).
The next stage is to identify the search terms in each ‘facet’ which best capture the subject. The group of search terms covering each facet of the review question should include a range of text words (free text to be searched in the title or abstract of studies). Text words and their variants can be identified by reading relevant reviews and primary studies identified during earlier searches or a pre-assessment of the literature. Information on the subject indexing used by databases can be found by consulting the relevant indexing manuals and by noting the manner in which key retrieved articles have been indexed by a given database.
The final search strategy will be developed by an iterative process in which groups of terms are used, perhaps in several permutations, to identify the combination of terms that seems most sensitive in identifying relevant studies. This requires skilled adaptation of search strategies based on knowledge of the subject area, the subject headings and the combination of ‘facets’ which best capture the topic.