Prognostic significance of preoperative platelet count in patients with gallbladder cancer

Figure 1 Receiver operating characteristic curve analysis to predict the gallbladder cancer stage. Each point on the receiver operating characteristic (ROC) curve corresponds to a value of platelet count (PLT). A diagonal line at 45°, known as the line of chance, would result from a test that allocated subjects randomly. In general, a good cutoff point produces high sensitivity and high specificity, which could be interpreted as selecting the point on the ROC curve with the largest vertical distance from the line of chance. The area under the ROC curve (AUC) indicates the diagnostic power of PLT. An ROC curve for survival prediction was plotted to verify the optimum cutoff point for PLT, which was 178 × 10⁹/L. The AUC for PLT was 79.8% (95%CI: 0.737-0.858), with a sensitivity of 74.6% and a specificity of 72.2% by the Youden index.