A comparison of clinical outcomes from carotid artery stenting among US hospitals

Abstract

Background: The Centers for Medicare and Medicaid Services require hospitals performing carotid artery stenting (CAS) to recertify the quality of their programs every 2 years, but currently this involves no explicit comparisons of postprocedure mortality across hospitals. Hence, the current recertification process may fail to identify hospitals that are performing poorly in relation to peer institutions. Our objective was to compare risk-standardized procedural outcomes across US hospitals that performed CAS and to identify hospitals with statistically high postprocedure mortality rates.

Methods and results: We conducted a retrospective cohort study of Medicare beneficiaries who underwent CAS from July 2009 to June 2011 at 927 US hospitals. Thirty-day risk-standardized mortality rates were calculated using the Hospital Compare statistical method, a well-validated hierarchical generalized linear model that included both patient-level and hospital-level predictors. Claims were examined from 22 708 patients undergoing CAS, with a crude 30-day mortality rate of 2.0%. Risk-standardized 30-day mortality rates after CAS varied from 1.1% to 5.1% (P<0.001 for the difference). Thirteen hospitals had risk-standardized mortality rates that were statistically (P<0.05) higher than the national mean. Conversely, 5 hospitals had risk-standardized mortality rates that were statistically (P<0.05) lower than the national mean.

Conclusions: We used administrative claims to identify several CAS hospitals with excessively high 30-day mortality after carotid stenting. When combined with information currently used by Medicare for CAS recertification, such as clinical registry data and program reports, clinical outcomes comparisons could enhance Medicare's ability to identify hospitals that are questionable candidates for recertification.

Keywords: Medicare; outcome assessment (health care).

Figure 1. Distribution of Crude and Risk-Standardized Mortality Rates after CAS Among U.S. Hospitals

The figure includes box-plots, with the lower and upper boundaries of the box indicating the 25^th and 75^th percentiles of the data, and the median indicated by the line subdividing the box. The “whiskers” encompass all other observations except those that are 1.5 times the interquartile range above or below the box boundaries. These individual values are signified by dots. The left boxplot indicates the distribution of U.S. hospital crude CAS 30-day mortality rates. The right boxplot indicates the distribution of U.S. hospital risk-standardized CAS 30-day mortality rates. The blue horizontal line indicates the national mean 30-day CAS mortality rate.

Figure 2. Risk-Standardized Mortality Rates Among Hospitals (n=13) with Rates Significantly Above the National Mean

Each hospital’s risk-standardized mortality rate is indicated by the black dot, with the 95% confidence interval for the mortality rate denoted by the error bars. The data are arranged from left to right in ascending order of each hospital’s risk-standardized mortality rate. The red horizontal line indicates the national mean 30-day CAS mortality rate.