following sections is the evaluation of the clinical efficacies of therapies by RCTs and systematic reviews.

SOURCES OF INFORMATION ON HIGH-QUALITY EVIDENCE

Two main sources of information about published RCTs and systematic reviews are The Cochrane Library and MEDLINE. Critical reviews of reviews and Agency for Healthcare Research and Quality (AHRQ) Evidence Reports summarize the information by using rigorous and objective methods. National Institutes of Health (NIH) Consensus Statements incorporate evidence from RCTs and systematic reviews together with the judgments of a panel of nonadvocate, nongovernmental experts, to reach a decision about the efficacy and safety of a particular treatment.

MEDLINE

MEDLINE, a product of the National Library of Medicine, is an extensive bibliographic database covering all areas of clinical medicine and biomedical research. The bibliographic citations and abstracts indexed in MEDLINE are from more than 4,600 biomedical journals published worldwide, and the database includes information on all randomized trials in MEDLINE-indexed journals, regardless of the methodological quality or clinical relevance. MEDLINE is accessible online and is free of charge to the public, and most of its 12 million citations are available in English, at least as abstracts. The database includes studies published since 1966, the year that MEDLINE began, and is updated on a regular basis (National Library of Medicine, 2002).

In recent years, relevant indexing terms have been introduced on MEDLINE to facilitate queries on trials and systematic reviews related to CAM. MEDLINE introduced the publication type “randomized controlled trial” for specific RCTs in 1991 and the subject subset “systematic review” in 2001. The subject subset “CAM” was introduced in 2001 and includes all records identified through the execution of a complex, highly sensitive search strategy designed to identify all records in the MEDLINE database related to CAM. The introduction of these terms allows interested individuals to make simple queries of MEDLINE to estimate changes in the evidence base for CAM from the results of RCTs and systematic reviews over time. Figure 5-1 charts the tremendous growth in the number of RCTs over the past 20 years, and Figure 5-2 shows that the rate of increase of reviews and meta-analyses is even greater. These increases parallel general trends of growth in trials and meta-analyses over the past twenty years (Lee et al., 2001). Despite these developments, however, limitations of MEDLINE persist: not all studies in MEDLINE are indexed with the appropriate terms



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