Assessment of a university of California, Los Angeles 4-variable risk score for advanced heart failure

Background: The 4-variable risk score from University of California, Los Angeles (UCLA) demonstrated superior discrimination in advanced heart failure, compared to established risk scores. However, the model has not been externally validated, and its suitability as a selection tool for heart transplantation (HT) and left ventricular assist device (LVAD) is unknown. Methods and Results: We calculated the UCLA risk score (based on B-type natriuretic peptide, peak VO₂, New York Heart Association class, and use of angiotensin-converting enzyme inhibitor or angiotensin receptor blocker) in 180 patients referred for HT. The outcome was survival free from urgent transplantation or LVAD. The model-predicted survival was compared to Kaplan- Meier's estimated survival at 1, 2, and 3 years. Model discrimination and calibration were assessed. During a mean follow-up of 2.1 years, 37 (21%) events occurred. One-, 2-and 3-year observed event-free survival was 88%, 81%, and 75%, and the observed/predicted ratio was 0.97, 0.96, and 0.97, respectively. Time-dependent receiver operating characteristic curve analyses demonstrated good discrimination overall (1-year area under curve, 0.801; 2-year, 0.774; 3-year, 0.837), but discrimination between the 2 highest risk groups was poor. The difference between observed and predicted survival ranged from -14 to +17 percentage points, suggesting poor model calibration. Fairly similar results were found when the analyses were repeated in 715 patients after multivariate imputation of missing data. Conclusions: The UCLA 4-variable risk model calibration was inconsistent and high-risk discrimination was poor in an external validation cohort. Further model assessment is warranted before widespread use.