RACHS-ANZ: A Modified Risk Adjustment in Congenital Heart Surgery Model for Outcome Surveillance in Australia and New Zealand

Abstract

Background: Outcomes for pediatric cardiac surgery are commonly reported from international databases compiled from voluntary data submissions. Surgical outcomes for all children in a country or region are less commonly reported. We aimed to describe the bi-national population-based outcome for children undergoing cardiac surgery in Australia and New Zealand and determine whether the Risk Adjustment for Congenital Heart Surgery (RACHS) classification could be used to create a model that accurately predicts in-hospital mortality in this population. Methods and Results: The study was conducted in all children's hospitals performing cardiac surgery in Australia and New Zealand between January 2007 and December 2015. The performance of the original RACHS-1 model was assessed and compared with an alternative RACHS-ANZ (Australia and New Zealand) model, developed balancing discrimination with parsimonious variable selection. A total of 14 324 hospital admissions were analyzed. The overall hospital mortality was 2.3%, ranging from 0.5% for RACHS category 1 procedures, to 17.0% for RACHS category 5 or 6 procedures. The original RACHS-1 model was poorly calibrated with death overpredicted (1161 deaths predicted, 289 deaths observed). The RACHS-ANZ model had better performance in this population with excellent discrimination (Az-ROC of 0.830) and acceptable Hosmer and Lemeshow goodness-of-fit (P=0.216). Conclusions: The original RACHS-1 model overpredicts mortality in children undergoing heart surgery in the current era. The RACHS-ANZ model requires only 3 risk variables in addition to the RACHS procedure category, can be applied to a wider range of patients than RACHS-1, and is suitable to use to monitor regional pediatric cardiac surgery outcomes.