Too many clinical practice guidelines are based on expert opinion, rather than clinical trials and meta-analysis, according to a new report from the National Academy of Sciences’ Institute of Medicine (IOM). Findings published in late September by an expert panel indicate that in some cases half of recommendations in a clinical area are based on “expert opinion, case studies or standards of care” rather than evidence derived from clinical studies. The panel cites research published in 2011 indicating that only 14 percent of recommendations of the Infectious Diseases Society of America were based on more than a single clinical trial, while more than half were found to have been based solely on expert opinion. A similar analysis of recommendations from the American College of Cardiology and the American Heart Association found that most practice guidelines hadn’t been subjected to controlled trials. “The inadequacy of the evidence base for clinical guidelines has consequences for the evidence base for care delivered,” warn the report authors. Best Care at Lower Cost: The Path to Continuously Learning Health Care in America is available at the IOM website at www.iom.edu.