Case complexity scores in congenital heart surgery: A comparative study of the Aristotle Basic Complexity score and the Risk Adjustment in Congenital Heart Surgery (RACHS-1) system

Observed (gray) and predicted (black) probability of in-hospital death over calendar year of operation. A, For ABC levels (score range), 1 (1.5-5.9), 2 (6-7.9), 3 (8-9.9), and 4 (10-15). B, For RACHS-1 categories 1, 2, 3, 4, and 5/6.

The predictive value of robust logistic models of ABC, RACHS-1, and both scores combined. Unadjusted models, models adjusted for the calendar year of operation, and models adjusted for calendar year of operation and the child’s age at operation are presented. The predictive value is represented by the model LR and adequacy index (% likelihood ratio χ² attributable to the nested model, which does include both ABC and RACHS-1; see Methods). P values shown are of an LR χ² test for nested models with 4 degrees of freedom.

The number of patients (Frequency) assigned to intervals of predicted risk by ABC, RACHS-1, or both with extreme (ie, very low [<1%] and very high [>15%]) scores predicted in-hospital mortality. Models with more frequent extreme predictions are more clinically useful. The cutoffs of 1% and 15% were approximately the 5th and 95th percentiles of predicted risk of in-hospital death.

Cumulative incidence plots of death before discharge versus discharge alive over time from the day of operation (time 0). A, For ABC levels (score range), 1 (1.5-5.9), 2 (6-7.9), 3 (8-9.9), and 4 (10-15). B, For RACHS-1 categories 1, 2, 3, 4, and 5/6. The time point (x-axis point) corresponding to a cumulative incidence (y-axis point) of 0.5 on the dashed curve represents the mean time to discharge from hospital.