In many ways, if customary care and evidence-based research got together and had a baby, it would be the clinical practice guideline. Clinical Practice Guidelines (CPGs) standardize treatment by placing patients with particular diagnoses on a relatively uniform pathway. CPG pathways are found by identifying and standardizing successful customary care practices or through research generated in evidence-based studies.
Unsurprisingly, the two often overlap.
Clinical guidelines with benchmark quality care rooted in science have been shown to improve patient safety. For example, in 1985, anesthesiologists, motivated by increasing malpractice premiums and studies showing that human error was the most frequent cause of patient harm, undertook a thorough examination of their practices. After reviewing claims from 35 different insurers, the specialty of anesthesiology developed practice guidelines specifically aimed at reducing preventable harm to patients. As a result, “the risk of death from anesthesia dropped from 1 in 5000 to about 1 in 250,000.”
While the CPGs are valuable adjuncts, physicians recognize that adherence to guidelines does not make them exempt from scientific uncertainty. CPG recommendations are usually labeled with an explicit grade according to the strength of the underlying science. Recommendations from EBM reviews may be labeled as “Class I – Standards,” “Class II – Guidelines,” and “Class III – Options.” Classifications imply decreasing levels of scientific support. “Class I recommendations are the ‘do’s’; Class III recommendations are the ‘don’ts’; and Class II recommendations are the ‘maybes.’”
Even the “do’s” do not make clinical decisions for physicians; rather, they must be applied to individual patients and clinical situations based on value judgments, both by physicians and their patients. However, strong guidelines change the anchor point for the decision from beliefs about what works to evidence of what works. Armed with such a guideline, the physician and patient must still make treatment decisions, but they are better informed than decisions made without evidence.
In the search to identify a standard of care, CPGs based on EBM are a strong contender. CPGs serve as a rational justification for physician decisions and, with an applicable diagnosis, provide an escape fire solution to individual liability when the patient’s interests are best served through a treatment modality that differs from custom.
 George J. Annas, J.D., M.P.H., “The Patient’s Right to Safety – Improving the Quality of Care through Litigation against Hospitals,” New England Journal of Medicine, May 11, 2006.  Id.  Id.  David M. Eddy, Clinical Decision Making: From Theory to Practice. Designing a Practice Policy. Standards, Guidelines, and Options, 263 JAMA 3077, 3081 (1990).  Sanjaya Kumar and David Nash, “Health Care Myth Busters: Is There a High Degree of Scientific Certainty in Modern Medicine?”, http://www.scientificamerican.com/article/demand-better-health-care-book/.  Chris Taylor, MD, MBA, The Use of Clinical Practice Guidelines in Determining Standard of Care, 35 J. Legal Med. 273, 274 (2014). CPGs and algorithms are associated with a number of challenges. One challenge has to do with the validity or “clinical weight” behind the individual CPG. The National Institutes of Health database of biomedical literature generated 6,793 English-language references for “clinical practice guidelines” published in 2011. This proliferation of CPGs has led to significant variations in scientific validity, reliability, and usability. Because of these variations, “standardization of the standards” has been advocated, and attempts have been made to formalize the development and reporting of CPGs