Ranking hospitals on surgical mortality: the importance of reliability adjustment.
OBJECTIVE
We examined the implications of reliability adjustment on hospital mortality with surgery.


METHODS
We used national Medicare data (2003-2006) for three surgical procedures: coronary artery bypass grafting (CABG), abdominal aortic aneurysm (AAA) repair, and pancreatic resection.


METHODS
We conducted an observational study to evaluate the impact of reliability adjustment on hospital mortality rankings. Using hierarchical modeling, we adjusted hospital mortality for reliability using empirical Bayes techniques. We assessed the implication of this adjustment on the apparent variation across hospitals and the ability of historical hospital mortality rates (2003-2004) to forecast future mortality (2005-2006).


RESULTS
The net effect of reliability adjustment was to greatly diminish apparent variation for all three operations. Reliability adjustment was also particularly important for identifying hospitals with the lowest future mortality. Without reliability adjustment, hospitals in the "best" quintile (2003-2004) with pancreatic resection had a mortality of 7.6 percent in 2005-2006; with reliability adjustment, the "best" hospital quintile had a mortality of 2.7 percent in 2005-2006. For AAA repair, reliability adjustment also improved the ability to identify hospitals with lower future mortality. For CABG, the benefits of reliability adjustment were limited to the lowest volume hospitals.


CONCLUSIONS
Reliability adjustment results in more stable estimates of mortality that better forecast future performance. This statistical technique is crucial for helping patients select the best hospitals for specific procedures, particularly uncommon ones, and should be used for public reporting of hospital mortality.
Dimick
Justin B
JB
Department of Surgery, University of Michigan, M-SCORE offices, 211 N Fourth Avenue, Suite 301, Ann Arbor, MI 48104, USA. jdimick@umich.edu
Staiger
Douglas O
DO
Birkmeyer
John D
JD
D017052:Hospital Mortality; D006761:Hospitals / Q000145:classification* / Q000592:standards*; D006801:Humans; D015203:Reproducibility of Results; D013514:Surgical Procedures, Operative / Q000401:mortality* / Q000706:statistics & numerical data*