Net Reclassification Index Statistics Do Not Help Assess New Risk Models
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Updated: Aug 21, 2025

An R-Based Landscape Validation of a Competing Risk Model
Published on: September 16, 2022
1From the Department of Biostatistics, University of Washington School of Public Health, 3980 15th Ave NE, Box 351617, Seattle, WA 98195.
Abstract:
When evaluating a new risk factor for disease (eg, a measurement from imaging studies), many investigators examine its value above and beyond existing biomarkers and risk factors. They compare the performance of an "old" risk model using established predictors and a "new" risk model that adds the new factor. Net reclassification index (NRI) statistics are a family of metrics for comparing two risk models. NRI statistics became popular in some medical fields and have appeared in high-impact journals. This article reviews NRI statistics and describes several issues with them. Problems include unacceptable statistical behavior, incorrect statistical inferences, and lack of interpretability. NRI statistics are unhelpful (at best) and misleading (at worst).
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