Definition of race and outcomes. The race variable used in this study was derived from the HCUP database and included four groups: White, Black, Hispanic, and Asian/Pacific Islander. Information on race and ethnicity was provided by the state-level databases and was combined by the HCUP into a single race variable, giving ethnicity precedence over race. For example, if a patient was of Black racial group and Hispanic ethnicity, then he/she was classified as a member of the “Hispanic” racial group. This classification was used in previous analyses using HCUP data79. The outcome variable was the rates of being sent home among patients who visited the ED and had a primary discharge code for AMI and unstable angina. To identify patients who had a discharge diagnosis of AMI, we used the ICD-9 codes of 410.0 through 410.9 as the primary discharge code for years 2008, 2011, and 2014, and ICD-10 codes of I21.0-I21.02, I21, I21.1- I21.4, I21.11, I21.21, I21.29, I24.8, I21A, I21.A1, and I21.A9 for years 2016 and 2017. For identification of unstable angina, we used the primary ICD-9 discharge codes of 411.1, 411.8 and 411.89 for years 2008, 2011, and 2014 and ICD-10 discharge codes of I25.110, I12.00, and I12.0 for years 2016 and 2017.
