Published in:
01-12-2015 | Viewpoint
Why the C-statistic is not informative to evaluate early warning scores and what metrics to use
Authors:
Santiago Romero-Brufau, Jeanne M. Huddleston, Gabriel J. Escobar, Mark Liebow
Published in:
Critical Care
|
Issue 1/2015
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Abstract
Metrics typically used to report the performance of an early warning score (EWS), such as the area under the receiver operator characteristic curve or C-statistic, are not useful for pre-implementation analyses. Because physiological deterioration has an extremely low prevalence of 0.02 per patient-day, these metrics can be misleading. We discuss the statistical reasoning behind this statement and present a novel alternative metric more adequate to operationalize an EWS. We suggest that pre-implementation evaluation of EWSs should include at least two metrics: sensitivity; and either the positive predictive value, number needed to evaluate, or estimated rate of alerts. We also argue the importance of reporting each individual cutoff value.