The Hazards of Evidence-Based Medicine: Assessing Variations in Care

Assessing quality of care frequently involves using measures of processes of care, such as Medicare's 25 quality metrics.¹ Adherence to these processes is thought to lead to improved outcomes. For example, the Surgical Care Improvement Project was introduced in 2006, with the goal of reducing surgical complications by 25% by 2010.² Based on observational studies demonstrating associations between process and outcomes, experts concluded that adherence to this series of process measures would result in better care. Medicare adopted these and published them on its Hospital Compare Web site¹ as measures of hospital quality. However, for some process measures, studies have shown that adherence to these measures is not necessarily associated with improved outcomes. This has been the case for perioperative antibiotic use and postoperative wound infection³ and for acute myocardial infarction, heart failure, and pneumonia.⁴ More worrisome is that in some cases, adherence to the prescribed process measure may be associated with considerable harm, such as with tight glucose control in critically ill patients.⁵