Cindex: Concordance index for right censored survival time data

In SurvMetrics: Predictive Evaluation Metrics in Survival Analysis

Concordance index for right censored survival time data

Description

Concordance index is a rank correlation measures between a variable X and a possibly censored variable Y, with event/censoring indicator. In survival analysis, a pair of patients is called concordant if the risk of the event predicted by a model is lower for the patient who experiences the event at a later timepoint. The concordance probability (C-index) is the frequency of concordant pairs among all pairs of subjects. It can be used to measure and compare the discriminative power of a risk prediction models.

Usage

Cindex(object, predicted, t_star = -1)

Arguments

object	object of class Surv created by Surv function.
predicted	a vector containing the predicted survival time or probability of each observation.
t_star	the timepoint at which the C-index you want to calculate.

Details

Pairs with identical observed times, where one is uncensored and one is censored, are always considered usuable (independent of the value of tiedOutcomeIn), as it can be assumed that the event occurs at a later timepoint for the censored observation.

For uncensored response the result equals the one obtained with the functions rcorr.cens and rcorrcens from the Hmisc package (see examples).

Value

Estimates of the C-index.

Author(s)

Hanpu Zhou [e-mail]

References

Ishwaran, H. , Kogalur, U. B. , Blackstone, E. H. , & Lauer, M. S. . (2008). Random survival forests. Journal of Thoracic Oncology Official Publication of the International Association for the Study of Lung Cancer, 2(12), 841-860.

Kang, L. , Chen, W. , Petrick, N. A. , & Gallas, B. D. . (2015). Comparing two correlated c indices with right-censored survival outcome: a one-shot nonparametric approach. Statistics in Medicine, 34(4).

TA Gerds, MW Kattan, M Schumacher, and C Yu. Estimating a time-dependent concordance index for survival prediction models with covariate dependent censoring. Statistics in Medicine, Ahead of print:to appear, 2013. DOI = 10.1002/sim.5681

Wolbers, M and Koller, MT and Witteman, JCM and Gerds, TA (2013) Concordance for prognostic models with competing risks Research report 13/3. Department of Biostatistics, University of Copenhagen

Andersen, PK (2012) A note on the decomposition of number of life years lost according to causes of death Research report 12/2. Department of Biostatistics, University of Copenhagen

Paul Blanche, Michael W Kattan, and Thomas A Gerds. The c-index is not proper for the evaluation of-year predicted risks. Biostatistics, 20(2): 347–357, 2018.

Examples

library(survival)
time <- c(1, 1, 2, 2, 2, 2, 2, 2)
status <- c(0, 1, 1, 0, 1, 1, 0, 1)
predicted <- c(2, 3, 3, 3, 4, 2, 4, 3)
Cindex(Surv(time, status), predicted)

SurvMetrics documentation built on April 4, 2025, 5:03 a.m.