Levels of evidence supporting drug, device, and other recommendations in the American Heart Association/American College of Cardiology guidelines.

Clinical guideline documents reflect the evidence supporting clinical practice, but few recommendations in cardiovascular guidelines are supported by evidence from randomized controlled trials (RCTs), the highest level of evidence. Incentives for generating evidence from RCTs differ by topic of guideline recommendation, and it is uncertain whether evidence supporting guideline recommendations differs based on the topic of the recommendation. METHODS We abstracted recommendation statements from current ACC/AHA guideline documents (2008-2019). Two reviewers independently characterized each statement into categories based on its primary topic: pharmaceutical, device, non-invasive or minimally invasive therapeutic procedure, surgery, diagnostic invasive procedure or non-invasive imaging, laboratory, care strategies, health services or policy, history/physical examination, lifestyle or counseling. We determined the number and proportion of recommendations in each category characterized as level of evidence (LOE) A (supported by multiple RCTs), B (supported by a single RCT or observational data), and C (supported by expert opinion or limited data). RESULTS Of 2934 recommendations from 29 clinical guideline documents, 784 (26.7%) were primarily about pharmaceuticals, 503 (17.1%) diagnostic invasive procedure or non-invasive imaging, 366 (12.5%) devices, 349 (11.9%) care strategies, 274 (9.3%) surgery, 216 (7.4%) therapeutic procedures, 162 (5.5%) lifestyle interventions or counseling, 160 (5.5%) health services, care delivery, or policy, 83 (2.8%) laboratory, and 37 (1.3%) elements of the history and physical. Across all recommendations, 257 (8.8%) were characterized as LOE A, with considerable variability by topic. 25.9% of lifestyle/counseling recommendations, 16.9% of lab recommendations, and 14.7% of drug recommendations were classified as LOE A, but