Is the New York Cardiac Surgery Reporting System model sensitive to changes in case mix?
OBJECTIVE: To assess the validity of using the standardized mortality ratio (SMR), based on the New York State Cardiac Surgery Reporting System (CSRS) prediction model to compare coronary artery bypass grafting (CABG) outcomes between hospitals. DESIGN: The study was designed as a retrospective study based on a database containing all patients undergoing isolated CABG surgery in New York State hospitals in 1996 (n = 20,078). In the first part of this study, a computer simulation was used to assess the impact of case mix variation on the SMR. A computer-intensive algorithm was used to create 5,000 random case mixes from the patients in the CSRS database. The SMR associated with each of the 5,000 case mixes was calculated using a resampling algorithm. The second part of this study was designed to determine whether the identity of quality outliers among all of the 32 hospitals in the CSRS database would change after adjusting for the effects of case mix on the SMR. The SMR associated with
