Most major cardiovascular society guidelines are not based on the highest level of evidence, new research shows.
The percentage of U.S. or European guidelines supported by evidence from multiple randomized controlled trials (RCTs) or a single large RCT (level of evidence A) did not increase between 2008 and 2018, Dr. Renato D. Lopes of Duke Clinical Research Institute in Durham, North Carolina, and colleagues found.
Cardiology illustration. Source: Getty
"The large majority of patient care recommendations were based on nonrandomized evidence, even class I ("should do") and class III ("should not do") recommendations," they note in a report in JAMA, published online March 19.
"These results demonstrate that efforts over the past decade to simplify and facilitate clinical trials have not yet translated into an evidence base better supported by RCTs," they add.
Dr. Lopes and colleagues reviewed American College Cardiology/American Heart Association (ACC/AHA) and European Society of Cardiology (ESC) clinical guideline documents for 2008-2018.
The 26 ACC/AHA guidelines included a total of 2,930 recommendations, 248 of which were level of evidence (LOE) A (8.5%). Half were LOE B (supported by data from observational studies or a single RCT), and 41.5% were LOE C (based on expert opinion only).
The 25 ESC guidelines included 3,399 recommendations, with 14.2% classified as LOE A, 31.0% LOE B and 54.8% LOE C.
"The lack of RCT evidence supporting most recommendations in the guidelines was compounded by variability among subspecialties within cardiovascular medicine; some subspecialty guidelines contained almost no LOE A recommendations," Dr. Lopes and his colleagues note.
"Although the ESC and ACC/AHA guidelines use similar evidence to generate recommendations, a greater proportion of recommendations overall in the ESC guidelines were classified as LOE A, highlighting differences in the way that these professional societies interpret data and make guideline recommendations, and/or hesitancy of guideline writing committees to categorize as LOE A recommendations based on evidence from RCTs that enrolled patients entirely in other regions of the world," they add.
Dr. Robert O. Bonow, who co-authored an editorial accompanying the study, told Reuters Health by phone, "We're never going to have enough randomized controlled trials to cover every aspect of what we do."
"Many times we just don't have those clinical trials because clinical trials are expensive and they're few and far between and many times they are funded by an industry sponsor," added Dr. Bonow, of Northwestern University Feinberg School of Medicine in Chicago. "The lack of strong evidence for many things we do does not mean necessarily we can't make strong recommendations about what we think are the best pathways for diagnosis and treatment, because we do have lots of literature, lots of data."
Dr. Lopes was not available for an interview by press time.
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