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Quality of Evidence Statement
HERC relies heavily on high quality evidence and evidence-based guidelines in making prioritization decisions, coverage guidances and other evidence-based reports.
The following source list illustrates how HERC and the Value-based Benefits Subcommittee (VbBS) view various types of evidence.  The existence of evidence in the form of a high-quality study design does not necessarily mean that the overall evidence on that topic will be considered high quality.  For instance, a high quality systematic review might find that the available studies have significant potential for bias and may conclude there is a low strength of evidence or insufficient evidence to support an intervention.
Lower quality evidence may sometimes be considered in situations where higher quality evidence is difficult to obtain (for example, in rare clinical conditions). 
The commission includes other factors into its decision making process, such as harms, treatment alternatives, health equity and the needs of specific subgroups when relevant data exists. 
HERC may consider various factors in evaluating a particular study, including:
·         Potential for bias
·         Clinical significance of outcomes studied
·         Strength and consistency of evidence, not just study quality
·         Study relevance based on population and health system characteristics
·         Conflicts of interests of the authors
The following sources generally produce high quality evidence and are preferred by HERC:
  • Agency for Healthcare Research and Quality (AHRQ)
  • Blue Cross/Blue Shield Center for Clinical Effectiveness
  • Canadian Agency for Drugs and Technologies in Health (CADTH)
  • Cochrane Library (Wiley Online Library)
  • Institute for Clinical and Economic Review (ICER)
  • Medicaid Evidence-based Decisions Project (MED)
  • National Institute for Health and Care Excellence (NICE)
  • Tufts Cost-effectiveness Analysis Registry
  • Veterans Administration Evidence-based Synthesis Program (ESP)
  • Washington State Health Technology Assessment Program
The following types of study designs can be considered high quality and are preferred by HERC:
  • Systematic reviews or metaanalyses of randomized controlled trials
  • Systematic reviews of prospective cohort studies
  • Evidence-based guidelines from trusted sources
The following types of study designs/documents can be considered lower quality and are often reviewed by HERC:
  • Guidelines issued by professional societies and advocacy organizations (e.g. American Heart Association)
  • Coverage decisions by private health plans (e.g. Aetna)
  • Well-conducted, peer-reviewed individual studies (experimental or observational)
The following types of evidence can be considered very low quality and are seldom reviewed by HERC:
  • Case reports, case series
  • Unpublished studies (posters, abstracts, presentations, non-peer reviewed articles)
  • Individual studies that are poorly conducted, do not appear in peer-reviewed journals, are inferior in design or quality to other relevant literature, or duplicate information in other materials under review by the Commission