Quantifying the impact of different approaches for handling continuous predictors on the performance of a prognostic model

Collins, Gary, Ogundimu, Emmanuel, Cook, Jonathan, Le Manach, Yannick and Altman, Douglas (2016) Quantifying the impact of different approaches for handling continuous predictors on the performance of a prognostic model. Statistics in Medicine, 35 (23). pp. 4124-4135. ISSN 0277-6715

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Official URL: http://dx.doi.org/10.1002/sim.6986

Abstract

Continuous predictors are routinely encountered when developing a prognostic model. Investigators, who are often non-statisticians, must decide how to handle continuous predictors in their models. Categorising continuous measurements into two or more categories has been widely discredited, yet is still frequently done because of its simplicity, investigator ignorance of the potential impact and of suitable alternatives, or to facilitate model uptake. We examine three broad approaches for handling continuous predictors on the performance of a prognostic model, including various methods of categorising predictors, modelling a linear relationship between the predictor and outcome and modelling a nonlinear relationship using fractional polynomials or restricted cubic splines. We compare the performance (measured by the c-index, calibration and net benefit) of prognostic models built using each approach, evaluating them using separate data from that used to build them. We show that categorising continuous predictors produces models with poor predictive performance and poor clinical usefulness. Categorising continuous predictors is unnecessary, biologically implausible and inefficient and should not be used in prognostic model development.

Item Type: Article
Uncontrolled Keywords: prognostic modelling; continuous predictors; dichotomisation
Subjects: B900 Others in Subjects allied to Medicine
G300 Statistics
Department: Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering
Depositing User: Becky Skoyles
Date Deposited: 24 Jun 2016 08:53
Last Modified: 14 Oct 2017 02:25
URI: http://nrl.northumbria.ac.uk/id/eprint/27171

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