Validation of the French Index for the Prediction of Waitlist Mortality in a New Cohort of Candidates

Abstract

We derived and validated from the cohort of patients registered on the national registry CRISTAL, between January 2010 and December 2014, the Candidate Risk Score (CRS), predicting waitlist mortality. The CRS, converted into the Cardiac Risk Index (CRI), ranging from 0 to 40, includes 4 variables, venoarterial extracorporeal membrane oxygenator (VA-ECMO) use, plasma concentrations of natriuretic peptides (NP), glomerular filtration rate (GFR) and total serum bilirubin level. This study aimed to validate the CRI within the cohort of candidates listed on the CRISTAL registry between January 2018 and March 2019. All patients, aged 16 years or older, registered on the national registry CRISTAL, for heart transplantation, between January 2018 and March 2019, without score exception, (N=617) were included. The main outcome was 3-month waitlist mortality or delisting for worsening medical condition. Survival curves were estimated using Kaplan Meier method. Three-month survival curves stratified by CRI category were compared with the log rank test. The CRI calibration was assessed by calculating the correlation between the observed and predicted 3-month mortality by CRI decile. The slope of the calibration straight line was calculated. The CRI showed a good discriminative capacity with 3-month survival ranging from 34.8% [17.7%-52.6%] and 63.4% [43.0%-78.2%] in the highest (35-40) and second highest (30-34) CRI categories to 97.7% [93.1%-99.3%] and 93.4% [84.7%-97.2%] in the lowest (0-14) and second lowest (15-20) CRI categories(Figure). The correlation between predicted and observed 3-month waitlist mortality was excellent (r=0.90) and the slope of the calibration straight line was 0.93. This study validates the use of the CRI as a predictor of waitlist mortality in adult candidates. Currently the CRI is the cornerstone of the French heart allocation system.