Background: Physician adherence to guidelines is often poor, but the reasons have not been completely studied. We investigated whether physician adherence to guidelines for percutaneous transluminal coronary angioplasty (PTCA) and coronary artery bypass grafting (CABG) varied by source, development methods, or the extent of their evidence-base.
Methods and results: We assessed adherence to guidelines developed by the American College of Cardiology/American Heart Association (ACC/AHA) for PTCA (1988 and 1993) and for CABG (1990) and guidelines developed by RAND for PTCA and CABG in 1990. We randomly sampled patients on Medicare who were undergoing coronary angiography in 5 states in 1991 and 1992, extracting clinical and laboratory data from medical records and using computer programs to classify the appropriateness of each procedure. A total of 543 PTCA and 676 CABG procedures were studied. By use of the 1988 ACC/AHA guidelines, 30% of PTCAs were rated class III (inappropriate), whereas 24% were class III by use of the 1993 guidelines. Only 1.5% of CABG procedures were class III with ACC/AHA guidelines. By use of RAND guidelines, 12% of PTCA and 9% of CABG procedures were classified as inappropriate.
Conclusions: Adherence to guidelines is higher when the recommendations are supported by evidence from randomized clinical trials (CABG). The credibility of the source and familiarity with the guidelines do not ensure compliance. When evidence is lacking, as with PTCA at the time of this study, guideline recommendations may lag behind appropriate changes in clinical practice. More frequent revisions coupled with on-line access have the potential to make guidelines more useful.