IDH1 and oligodendroglioma: When combining IDH1-R132H with ATRX loss as diagnostic biomarkers for discriminating between pGBM, oligodendroglioma (WHO grade II/III) and sGBM, astrocytoma (WHO grade II/III), the AUC was 0.7407 (sensitivity 53.33%, specificity 94.815%, Figure 3C).