The association between procedural volume and short-term mortality has been repeatedly demonstrated for coronary artery bypass graft (CABG) surgery.1- 3 By virtue of this association it has been proposed that procedural volume, which can be easily measured, be used as a surrogate for quality, which is difficult to define and measure. However, the strength of the association between volume and quality is inconsistent and dependent on many factors including the type of data used (clinical vs administrative4), the method of risk adjustment (none vs hierarchical vs logistic regression5), the age of the patient population, and the location of the population (California vs New York6), to name just a few. Thus, despite its adoption by the Leapfrog Group and others, volume is unlikely to ever serve as an adequate surrogate for quality. The article by Auerbach et al7 attempts to relate CABG volume to length of stay and adherence to quality measures to determine if volume is a surrogate for the value of care. However, these end points are primarily of interest and concern to hospital administrators, third party payers, and health care economists. Thus, relative to the central and dominant interest of the patient, they are second-order outcomes.
Brown DL. Measuring Outcomes of Coronary Artery Bypass SurgeryWhat Is Important and to Whom?. Arch Intern Med. 2010;170(14):1189-1190. doi:10.1001/archinternmed.2010.238