The relationship between the C-statistic and the accuracy of program-specific evaluations

Andrew Wey, Nicholas Salkowski, Bertram L. Kasiske, Melissa A. Skeans, Sally K. Gustafson, Ajay K. Israni, Jon J. Snyder

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

The C-statistic of the risk-adjustment model is often used to judge the accuracy of program evaluations. However, the C-statistic depends on the variability in risk for individual transplants and may be inappropriate for determining the accuracy of program evaluations. A simulation study investigated the association of the C-statistic with several metrics of program evaluation accuracy, including categorizing programs into the 5-tier system and identifying programs for regulatory review. The simulation study used data from deceased donor kidney-alone transplants for adult recipients in the program-specific reports released January 2018. A range of C-statistics was generated by changing the variability in risk for individual transplants. The C-statistic had no association with any metric of program evaluation accuracy. Instead, the number of expected events at a program was the most important factor. For example, Spearman's rho, which is the correlation of ranks, was −0.27 and −0.72 between the true program-specific hazard ratios and assigned tiers for programs with, respectively, <3 and >10 expected events. Presence of unadjusted risk factors did not modify the associations, although the accuracy of program evaluations was systematically lower. Therefore, the C-statistic provides no information on the accuracy of program evaluations.

Original languageEnglish (US)
Pages (from-to)407-413
Number of pages7
JournalAmerican Journal of Transplantation
Volume19
Issue number2
DOIs
StatePublished - Feb 2019
Externally publishedYes

Keywords

  • clinical research/practice
  • organ transplantation in general
  • Scientific Registry for Transplant Recipients (SRTR)
  • statistics

ASJC Scopus subject areas

  • Immunology and Allergy
  • Transplantation
  • Pharmacology (medical)

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