Clinical performance of the SHOX2 DNA methylation biomarker. Valid measurements were obtained from 523 patients (281 cases, 242 controls). A: SHOX2 DNA methylation values measured in cases (red) and controls (black). Low ΔΔCT indicate a low SHOX2 DNA methylation. A ΔΔCT = 0 refers to a sample showing the same methylation as the calibrator DNA (1%). B: Resulting sensitivity and specificity when using alternative cut-offs for patient stratification. C: Receiver Operating Characteristic (ROC) and the resulting Area Under the Curve (AUC).