Patients who were candidates for percutaneous coronary intervention (PCI) from 2003-2004 would have received different classifications according to guidelines established in 2001 and 2005.

Clinical practice guidelines (CPG) provide detailed recommendations for the delivery of health services. Evidence found in the existing literature is the basis for new guidelines. Because the evidence base is constantly changing, adherence to CPGs may be a misleading performance measure.

In 2001 and again in 2005, several organizations jointly published guidelines for PCI. The guidelines classify patients based on the likelihood that PCI is the appropriate treatment. For example, Class I procedures are for patients when there is general agreement that the procedure will be effective.

This article presents a study that analyzed changes in PCI classifications between the 2001 and 2005 guidelines. The authors applied the guidelines to actual PCI indications from the 2003-2004 National Coronary Data Registry (NCDR). The aim of the study was to determine if PCI classifications indicated in 2003-2004, reflected changes in the evidence base that occurred after the 2001 guidelines. The authors analyzed the 2005 PCI guidelines to determine what changes had occurred since 2001.

Key Findings:

• There were 284 new references for PCI appearing in the literature between 2001 and 2005.
• PCI in asymptomatic patients was changed from Class I in the 2001 guidelines to Class 2a in 2005.
• The majority of patients with a Class I indication in the 2001 guidelines changed classifications based on the 2005 guidelines.

This study found significant changes to PCI classifications in the 2005 guidelines; these changes suggest that adherence to clinical practice guidelines is not a valid measure of quality of care.