Levels of evidence in cardiovascular clinical practice guidelines

Clinical practice guidelines (CPGs) can be helpful in distilling the medical research literature for clinicians; however, the guidelines should acknowledge the variable methodological quality used in clinical research by tempering their recommendations with a 'levels of evidence' scale.

To evaluate the proportion of English-language cardiovascular CPGs that provide the user with recommendations graded according to a defined levels of evidence scale. In addition, to evaluate other key aspects important in the critical appraisal of CPGs.

CPGs for atrial fibrillation, congestive heart failure and myocardial infarction were identified by searching MEDLINE, a reference text of CPGs and the Internet. Each CPG was evaluated using a priori-defined criteria based on the Evidence-Based Medicine Working Group's paper on critical appraisal of CPGs, including use of a reproducible search strategy, method of obtaining consensus, peer review and testing in practice.

A total of 95 CPGs were evaluated. Only 13% graded their recommendations using a defined levels of evidence scale. In addition, few CPGs documented a reproducible search strategy or peer review process, and none had been formally tested in practice.

Reporting the levels of evidence for recommendations is an important component of CPGs, yet this system is not widely used.