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Original Investigation
March 19, 2019

Levels of Evidence Supporting American College of Cardiology/American Heart Association and European Society of Cardiology Guidelines, 2008-2018

Author Affiliations
  • 1Division of Cardiology and Duke Clinical Research Institute, Duke University, Durham, North Carolina
  • 2Duke Forge, Duke University School of Medicine, Durham, North Carolina
  • 3Department of Medicine, Stanford University, Stanford, California
  • 4Verily Life Sciences (Alphabet), South San Francisco, California
  • 5Department of Cardiology, Inselspital, University of Bern, Bern, Switzerland
  • 6Division of Cardiology, University of North Carolina School of Medicine, Chapel Hill
JAMA. 2019;321(11):1069-1080. doi:10.1001/jama.2019.1122
Key Points

Question  What proportion of recommendations in current American College of Cardiology/American Heart Association (ACC/AHA) and European Society of Cardiology (ESC) guidelines are supported by evidence from multiple randomized controlled trials (RCTs), and how has this changed over the past 10 years?

Findings  In this systematic review of 51 current guideline documents that included 6329 recommendations, 8.5% of recommendations in ACC/AHA guidelines and 14.3% of recommendations in ESC guidelines were classified as level of evidence A (supported by evidence from multiple RCTs), compared with 11.5% of recommendations in a systematic review of ACC/AHA guidelines conducted in 2009.

Meaning  Among recommendations in major cardiovascular society guidelines from 2008 to 2018, the proportion supported by evidence from RCTs remains small.

Abstract

Importance  Clinical decisions are ideally based on evidence generated from multiple randomized controlled trials (RCTs) evaluating clinical outcomes, but historically, few clinical guideline recommendations have been based entirely on this type of evidence.

Objective  To determine the class and level of evidence (LOE) supporting current major cardiovascular society guideline recommendations, and changes in LOE over time.

Data Sources  Current American College of Cardiology/American Heart Association (ACC/AHA) and European Society of Cardiology (ESC) clinical guideline documents (2008-2018), as identified on cardiovascular society websites, and immediate predecessors to these guideline documents (1999-2014), as referenced in current guideline documents.

Study Selection  Comprehensive guideline documents including recommendations organized by class and LOE.

Data Extraction and Synthesis  The number of recommendations and the distribution of LOE (A [supported by data from multiple RCTs or a single, large RCT], B [supported by data from observational studies or a single RCT], and C [supported by expert opinion only]) were determined for each guideline document.

Main Outcomes and Measures  The proportion of guideline recommendations supported by evidence from multiple RCTs (LOE A).

Results  Across 26 current ACC/AHA guidelines (2930 recommendations; median, 121 recommendations per guideline [25th-75th percentiles, 76-155]), 248 recommendations (8.5%) were classified as LOE A, 1465 (50.0%) as LOE B, and 1217 (41.5%) as LOE C. The median proportion of LOE A recommendations was 7.9% (25th-75th percentiles, 0.9%-15.2%). Across 25 current ESC guideline documents (3399 recommendations; median, 130 recommendations per guideline [25th-75th percentiles, 111-154]), 484 recommendations (14.2%) were classified as LOE A, 1053 (31.0%) as LOE B, and 1862 (54.8%) as LOE C. When comparing current guidelines with prior versions, the proportion of recommendations that were LOE A did not increase in either ACC/AHA (median, 9.0% [current] vs 11.7% [prior]) or ESC guidelines (median, 15.1% [current] vs 17.6% [prior]).

Conclusions and Relevance  Among recommendations in major cardiovascular society guidelines, only a small percentage were supported by evidence from multiple RCTs or a single, large RCT. This pattern does not appear to have meaningfully improved from 2008 to 2018.

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