2.5. Statistical analysis

Baseline patient characteristics were summarized using frequencies and percentages for discrete variables and medians and interquartile ranges (IQR) for continuous variables. VHR was considered to be the reference standard and the performance of the administrative comorbidity and procedure definitions was evaluated by calculating the positive predictive value (PPV), negative predictive value (NPV), sensitivity, specificity, and Cohen Kappa statistic, all with corresponding 95% Wald confidence intervals (CIs). As VHR contains exclusively STEMI patients, only sensitivity was calculated for evaluating the administrative STEMI definition. To assess and compare the discrimination of the 4 sets of administrative comorbidity case definitions, we modeled in-hospital mortality using logistic regression models that included the 7 comorbidities defined by each algorithm as well as age and sex, and reported the corresponding C statistics for each of the 4 models. Patients with missing values for comorbidities in the VHR registry were excluded from each comorbidity specific analysis but included in analyses for which their values were known. All analyses were conducted using SAS v9.4 (SAS Institute, Cary, NC). This study received approval from the University of Alberta Health Research Ethics Board.