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Dietary Supplements: A Framework for Evaluating Safety
tutes of Health (NIH) (AHRQ, 2000a, 2000b). The Southern California EPC/RAND completed an evidence-based report on S-adenosyl-L-methionine (SAMe) in 2002 for NCCAM (AHRQ, 2002b), and an evidence-based report on ephedra, released in February 2003, for NIH’s Office of Dietary Supplements and NCCAM (AHRQ, 2003a).
The EPC reports are based on a systematic analysis of the relevant scientific data (AHRQ, 2002c). The analyses are based on a weighting and ranking methodology and are dependent on judgments based on well-defined criteria. The reports are designed to differentiate the types and strength of evidence (AHRQ, 2002c). Due to the exhaustive nature of the reports, they are resource intensive.
The first step of an AHRQ review is to identify relevant citations following an exhaustive search of the literature in a variety of electronic databases. Additional citations are identified from bibliographies, manufacturers, and technical experts. Both English and non-English references are included in the search. In general, only published full articles are used, but additional unpublished information provided by authors of published studies may also be included (AHRQ, 2000a, 2000b).
Independent reviewers on the EPC staff read the titles and abstracts of all the identified citations and exclude those citations that do not meet defined selection criteria on types of participants, interventions, control groups, outcomes, and study designs. To assess adverse clinical events, all types of human studies are used (e.g., randomized controlled trials, prospective trials, and case-control and cohort studies). Data are abstracted from the literature and analyzed by independent reviewers with clinical and methodological expertise. The analysis includes an assessment of the internal validity and quality of the studies. The data analysis includes generation of evidence tables, graphical summaries, statistical tests, and meta-analyses. The results and conclusions of the analysis are summarized in an evidence report that contains conclusions on the current knowledge on the efficacy and adverse effects of the substance and provides recommendations for future research (AHRQ, 2000a, 2000b).
Nominations for clinical topics to be reviewed by an EPC are solicited through notices in the Federal Register. Topics must meet specific selection criteria including, “high incidence or prevalence in the general population and in special populations … ; significance for the needs of Medicare, Medicaid, and other federal health programs; high cost associated with a condition, procedure, treatment, or technology, whether due to the number of people needing care, high unit cost of care, or high indirect costs; controversy or uncertainty about the effectiveness or relative effectiveness of available clinical strategies or technologies and availability of scientific data to support the systematic review and analysis of the topic” (AHRQ, 2002a). Based on this process, the dietary supplements milk thistle, ephedra, garlic,