Index terms (also called controlled vocabulary or thesaurus terms) such as Medical Subject Headings (MeSH) in MEDLINE and EMTREE in EMBASE are assigned to records in electronic databases to describe the studies. MEDLINE and EMBASE employ few useful indexing terms for adverse effects; they include DRUG TOXICITY/ and ADVERSE DRUG REACTION SYSTEMS in MEDLINE and DRUG TOXICITY/ and ADVERSE DRUG REACTION/ in EMBASE. However, the most useful way to search for adverse effects is by using subheadings (Golder 2006). Subheadings can be attached to index terms to describe specific aspects, for example ‘side effects’ of drugs, or ‘complications’ of surgery, or they can be used where they are searched for attaching to any index term (floating subheadings). The subheadings used to denote data on adverse effects differ in the major databases MEDLINE and EMBASE, for example:
Aspirin/adverse effects (MEDLINE)
Acetylsalicylic-acid/adverse-drug-reaction (EMBASE)
In the above example, Aspirin is the MeSH term and adverse effects is the subheading; Acetylsalicylic-acid is the EMTREE term and adverse-drug-reaction is the subheading.
Within a database, studies may be (i) indexed under the name of the intervention together with a subheading to denote that adverse effects occurred, for example, Aspirin/adverse effects or Mastectomy/complications; or (ii) the adverse event itself may be indexed, together with the nature of the intervention, for example, Gastrointestinal Hemorrhage/ and Aspirin/ , or Lymphedema/ and Surgery/; or (iii) occasionally, an article may be indexed only under the adverse event, for example, Hemorrhage/chemically-induced.
Thus, no single index or subheading search term can be relied on to identify all data on adverse effects, but a combination of index terms and subheadings is useful in detecting reports of major adverse effects which the indexers are likely to regard as significant (Derry 2001).
Subheadings that can be used with the intervention or with all interventions (floated) and which may prove useful in MEDLINE are:
/adverse effects (NB if this subheading is exploded it will include the subheadings /poisoning and /toxicity)
/poisoning
/toxicity
/contraindications
Subheadings that can be used with the adverse outcome or with all outcomes (floated) and which may prove useful in MEDLINE are:
/chemically induced
/complications
Subheadings that can be used with the intervention or with all interventions (floated) and which may prove useful in EMBASE are:
/adverse drug reaction
/drug toxicity
Subheadings that can be used with the adverse outcome or with all outcomes (floated) and which may prove useful in EMBASE are:
/complication
/side effect