A New Risk Index for Predicting Outcomes among Patients Undergoing Carotid Endarterectomy in Large Administrative Data Sets

Background We developed and validated a new index to provide risk adjustment and to predict in-hospital patient mortality and other outcomes in patients undergoing carotid endarterectomy (CEA). Methods The primary endpoint was occurrence of stroke, cardiac complications, or death during hospitalization for CEA derived from the Nationwide Inpatient Sample. Multivariate logistic regression was performed to identify the effect of clinical and demographic factors on occurrence of the primary endpoint. Data from 2005 to 2006 (study period 1) were used to derive risk index score whereas data from 2007 to 2009 (study period 2) were used for validation of the risk index. Results A total of 120,633 patients with mean age in years [ ±SD] of 71.1[ ±9.5] (42.4% women) underwent CEA during the derivation period. The rate of occurrence of composite endpoint during study period 1 was 3.1%. Predictors of the composite endpoint were (odds ratio [OR], P value) as follows: age 70 years or older (1.15,.013 assigned 1 point), atrial fibrillation (3.18, <.0001 assigned 3 points), Congestive Heart Failure (CHF) (1.81, <.0001 assigned 2 points), cigarette smoking (1.64, <.0001 assigned 2 points), symptomatic status (1.87, <.001 assigned 2 points), and chronic renal failure (1.64, <.0001 assigned 2 points). When applied to the validation cohort (n = 71,222), patients with scores 0-1 (OR 1.6, 95% confidence interval [CI] 1.5-1.8), scores 2-3 (OR 4.0, 95% CI 3.8-4.3), scores 4-5 (OR 7.5, 95% CI 6.8-8.2), and scores greater than 5 (OR 10.9, 95% CI 9.8-12.2) had composite rates of endpoint. The receiver operating characteristic curve of the risk index was 68.5% [±SE 0.5%]. Conclusion New risk index will assist in risk adjustment for analyses of outcomes in large administrative data sets for comparative studies involving patients undergoing CEA.