ATRX and glioblastoma: Model performance on the external TCGA-GBM dataset was relatively poor for both ATRX (sensitivity = 0.75, specificity = 0.75, MCC = 0.29, AUC = 0.72) and IDH (sensitivity = 0.75, specificity = 0.66, MCC = 0.22, AUC = 0.63).