Appendix E contains a detailed summary of expert guidance on this chapter’s topics.


When healthcare decision makers turn to SRs to learn the potential benefits and harms of alternative health care therapies, it is with the expectation that the SR will provide a complete picture of all that is known about an intervention. Research is relevant to individual decision making, whether it reveals benefits, harms, or lack of effectiveness of a health intervention. Thus, the overarching objective of the SR search for evidence is to identify all the studies (and all the relevant data from the studies) that may pertain to the research question and analytic framework. The task is a challenging one. Hundreds of thousands of research articles are indexed in bibliographic databases each year. Yet despite the enormous volume of published research, a substantial proportion of effectiveness data are never published or are not easy to access. For example, approximately 50 percent of studies appearing as conference abstracts are never fully published (Scherer et al., 2007), and some studies are not even reported as conference abstracts. Even when there are published reports of effectiveness studies, the studies often report only a subset of the relevant data. Furthermore, it is well documented that the data reported may not represent all the findings on an intervention’s effectiveness because of pervasive reporting bias in the biomedical literature. Moreover, crucial information from the studies is often difficult to locate because it is kept in researchers’ files, government agency records, or manufacturers’ proprietary records.

The following overview further describes the context for the SR search process: the nature of the reporting bias in the biomedical literature; key sources of information on comparative effectiveness; and expert guidance on how to plan and conduct the search. The committee’s related standards are presented at the end of the section.

Planning the Search

The search strategy should be an integral component of the research protocol1 that specifies procedures for finding the evidence directly relevant to the SR. Items described in the protocol include,


See Chapter 2 for the committee’s recommended standards for establishing the research protocol.

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