Fig. 2

ROC curves and optimal core body temperature thresholds in °C for stage discrimination. For every possible threshold temperature, T°, sensitivity was defined as the proportion of patients in the higher stage group with a temperature below T°, and specificity as the proportion of patients in the lower stage group with a temperature equal to or above T°. The temperature that best distinguished between stages was taken as the temperature value that maximised the sum of sensitivity plus specificity. Using the estimated optimal thresholds increased (sensitivity + specificity) from 160 to 161 for the stage 1/2 threshold, from 146 to 147 for the stage 2/3 threshold, and from 131 to 135 for the Stage 3/4 threshold. Actual cut = accepted threshold for current clinical Swiss staging system; optimal cut = optimal threshold i.e. the temperature at which the sum of sensitivity + specificity is maximal; AUC = area under the curve