concordance index
A statistical measure used to evaluate the predictive accuracy of prognostic models in oncology outcomes research.
Full Definition
The concordance index (C-index) is a statistical measure that quantifies the ability of a prognostic model to correctly rank patients according to their risk of experiencing an event such as cancer recurrence or death. Values range from 0.5 (no predictive ability, equivalent to random chance) to 1.0 (perfect prediction). In breast cancer research, concordance indices are frequently used to validate prognostic tools, compare multigene assays, and assess the performance of clinical prediction models. A C-index above 0.7 is generally considered clinically useful, while values above 0.8 indicate strong predictive performance.
Usage
Usage note: Often abbreviated as C-index in statistical literature and research publications.
In Context
- "The 21-gene assay demonstrated a concordance index of 0.72 for predicting distant recurrence." — Validation study report
- "Model performance was assessed using the concordance index for time-to-event outcomes." — Statistical analysis plan