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Table 3 Performance of classification tree, original SAPS II, and recalibrated SAPS II in all patients in the independent validation set (n = 2,289)

From: Identification of high-risk subgroups in very elderly intensive care unit patients

  Classification tree SAPS II Recalibrated SAPS II
ROC-AUC ± SD 0.77 ± 0.01 0.77 ± 0.01 0.77 ± 0.01
Brier score 0.16 0.16 0.16
Threshold PPV    
   0.5 0.69 (0.64–0.73) 0.68 (0.64–0.72) 0.71 (0.67–0.76)
Died (n) 329 340 305
Predicted to die (n) 480 502 427
   0.7 0.85 (0.8–0.89) 0.78 (0.73–0.82) 0.81 (0.76–0.86)
Died (n) 196 241 176
Predicted to die (n) 230 309 215
   0.8 0.88 (0.83–0.91) 0.83 (0.77–0.87) 0.88 (0.81–0.92)
Died (n) 184 168 119
Predicted to die (n) 210 203 136
  1. Confidence intervals (CIs) of differences between PPVs (asterisk indicates statistical significance at the 0.05 level) are as follows. For classification tree versus SAPS II, the CIs for cutoffs of 0.5, 0.7, and 0.8 are -0.032 to 0.047, 0.023 to 0.121*, and -0.006 to 0.104, respectively. For classification tree versus recalibrated SAPS II, the CIs for cutoffs of 0.5, 0.7, and 0.8 are -0.07 to 0.011, -0.027 to 0.086, and -0.057 to 0.055, respectively. For recalibrated SAPS II versus SAPS II, the CIs for cutoffs of 0.5, 0.7, and 0.8 are 0.056 to 0.016*, 0.072 to 0.004*, and 0.087 to 0.003*, respectively. PPV, positive predictive value; ROC-AUC, area under the receiver operating characteristic curve; SAPS II, Simplified Acute Physiology Score II; SD, standard deviation.
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