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Clinical practice guidelines for cardiology are steeped more in expert opinion than scientific evidence

Research Activities, August 2009, No. 348

For more than two decades, the American College of Cardiology (ACC) and the American Heart Association (AHA) have published clinical practice guidelines to let clinicians know which treatments their contemporaries believe are best. A recent study by Judith M. Kramer, M.D., M.S., of the Duke Center for Education and Research on Therapeutics (CERT) and colleagues examined ACC/AHA guidelines issued from 1984 to 2008. It found that many guidelines are still based on expert opinion and not on the results of rigorous trials. Although the number of recommendations in the guidelines has increased over time, the majority of current recommendations are based on a lower certainty of evidence, the authors found.

Overall, just 11 percent of recommendations had level A status, while 48 percent were at level C, despite the fact that cardiology has a large research pool to draw upon for recommendations. Level A indicates that the recommendations are based on evidence from multiple randomized trials, whereas level C means that the recommendations are less scientifically rigorous and based on expert opinion, case studies, or standards of care. Even among the 1,305 guideline recommendations that the experts agreed evidence and general agreement existed for a procedure or treatment (class I recommendations), just 245 were given an A level of evidence. In contrast, 481 class I recommendations were given C levels of evidence.

The current system for generating research findings is inadequate for meeting providers' and patients' information needs, caution the authors. They recommend that the medical research community streamline clinical trials to further develop the evidence base and fund research to answer practical clinical questions so that guidelines are not so heavily based on expert opinion.

This study was funded in part by the Agency for Healthcare Research and Quality (HS10548) to the Duke CERT. For more information on the CERTs program, visit

See "Scientific evidence underlying the ACC/AHA clinical practice guidelines," by Pierluigi Tricoci, M.D., M.H.S., Ph.D., Joseph M. Allen, M.A., Dr. Kramer, and others in the February 25, 2009, Journal of the American Medical Association 301(8), pp. 831-841.

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Page last reviewed August 2009
Internet Citation: Clinical practice guidelines for cardiology are steeped more in expert opinion than scientific evidence: Research Activities, August 2009, No. 348. August 2009. Agency for Healthcare Research and Quality, Rockville, MD.