Fig. 1
From: Why the C-statistic is not informative to evaluate early warning scores and what metrics to use
PPV as a function of prevalence for two sample scores (EWS): score A (blue), with a sensitivity of 99Â % and a specificity of 99Â %; and score B (red), with a sensitivity of 99Â % and a specificity of 96Â %. a Full range of possible PPV and prevalence, from 0 to 1. b Region of prevalence <0.1, adding a line to show an example prevalence of 0.02 (corresponding to an estimate of the rate of physiological deterioration of inpatients). A decrease of only 3Â % in specificity can mean a 50Â % decrease in PPV: from 0.33 to 0.66