An examination of clinical practice guidelines issued by the American College of Cardiology (ACC) and the American Heart Association (AHA) for treating cardiovascular (CV) disease has revealed that current recommendations are largely based on lower levels of evidence or expert opinion, according to a study this week in the Journal of the American Medical Association.

For more than 20 years, the ACC and the AHA have released clinical practice guidelines to provide recommendations on care of patients with CV disease.

Whether the increase in publication of studies concerning cardiovascular disease has resulted in guideline recommendations with more certainty and supporting evidence is not known.

Pierluigi Tricoci, MD, PhD, of Duke University in Durham, N.C., and colleagues examined the changes in recommendations in ACC/AHA CV guidelines and evaluated the adequacy of evidence behind current guideline recommendations. The analysis included data from ACC/AHA practice guidelines issued from 1984 to September 2008. The researchers examined 53 guidelines on 22 topics, including a total of 7,196 recommendations.

Considering only the current guidelines with at least one revision, the total number of recommendations has increased 48 percent from the first guideline to the current version. Overall, the guidelines shifted to more class II recommendations and fewer class III recommendations, while the use of class I recommendations remained fairly constant over time.

The investigators reported that the 16 current guidelines reporting levels of evidence, comprising a total of 2,711 recommendations, classify 314 recommendations as level of evidence A (median of 11 percent), and 1,246 with level of evidence C (median of 48 percent).

Among all 1,305 class I recommendations of guidelines reporting level of evidence, only 245 have level of evidence A (median, 19 percent), with 481 (median, 36 percent) having a level of evidence C, according to the authors. Level of evidence significantly varies across categories of guidelines (disease, intervention or diagnostic) and across individual guidelines.

"Our finding that a large proportion of recommendations in ACC/AHA guidelines are based on lower levels of evidence or expert opinion highlights deficiencies in the sources of definitive data available for the generation of cardiovascular guidelines," the authors wrote.

"To remedy this problem, the medical research community needs to streamline clinical trials, focus on areas of deficient evidence, and expand funding for clinical research. In addition, the process of developing guidelines needs to be improved with information about the impact that recommendations based on lower levels of evidence has on clinical practice. Finally, clinicians need to exercise caution when considering recommendations not supported by solid evidence," they concluded.

In an accompanying editorial, Terrence M. Shaneyfelt, MD, and Robert M. Centor, MD, of the University of Alabama School of Medicine in Birmingham, wrote that if clinical practice guidelines are going to continue to exist, they need to undergo major changes.

"However, it seems unlikely that substantial change will occur because many guideline developers seem set in their ways," Shaneyfelt and Centor wrote. "If all that can be produced are biased, minimally applicable consensus statements, perhaps guidelines should be avoided completely. Unless there is evidence of appropriate changes in the guideline process, clinicians and policy makers must reject calls for adherence to guidelines. Physicians would be better off making clinical decisions based on valid primary data."

In response to this study, both ACC and AHA have responded. “There are gaps in the evidence base for patient care, gaps that could be eliminated if more clinical research were funded, especially comparative effectiveness research that specifically compares one kind of diagnostic procedure or treatment with another,” said W. Douglas Weaver, MD, ACC president. “Improving our evidence base can lead to even greater improvements in treatment and in saving lives.”

“Can we do better? Certainly, actually in several ways,” said Tim Gardner, MD, AHA president. “We can do a better job of communicating those best practices to providers and ensuring they are used when they are the right treatment for the patient. And we can continue to advocate for adequate funding and other improvements in our clinical research infrastructure. We can continue to make an important difference.”