Background: The evaluation of adverse effects data is essential in
systematic reviews. However, information on adverse effects can be
retrieved from a wide range of sources that differ from those used in
efficacy. The value of such sources is uncertain. Objectives: To provide an
overview of methodological studies, which have investigated the use of
different sources of information for adverse effects. Methods: To identify
relevant studies, searches undertaken included ten bibliographic databases
(including MEDLINE and EMBASE), handsearching key journals and
conference proceedings, reference checking, contacting experts, and
citation searches. A research study was considered eligible for inclusion if it
assessed the effectiveness of two or more data sources for adverse effects.
Two reviewers extracted data on the difference in retrieval of adverse
effects data according to information source. Results: Eight studies met
the inclusion criteria. All studies included MEDLINE in their list of sources
for comparison. The number of sources included in each study varied
widely from 2 to 24. Five studies included both MEDLINE and EMBASE; all
indicated that searching EMBASE resulted in the retrieval of more relevant
references than MEDLINE. Two studies indicated the potential value of
Derwent Drug File (previously RingDoc) above EMBASE and MEDLINE. Two
out of three studies indicated that MEDLINE and EMBASE retrieved more
relevant references than TOXLINE or contacting manufacturers. Two
valuations included IPA and in both IPA retrieved the lowest number of
relevant records. Generalisability is a major limitation as five of the eight
included studies were conducted over 10 years ago. Many available data
sources remain unevaluated. Methodological considerations with the
studies identified included sponsorship from the databases evaluated,
small numbers of relevant records, and a lack of evaluation of the cost or
impact of searching the sources specified. Conclusions: The included
studies showed some level of agreement on those sources which provide
the largest number of relevant records on adverse effects for a systematic
review. However, none of the studies looked into whether inclusion of
these additional records would have influenced the results of a review.