IDH1 and diffuse astrocytoma: PAM analysis of differentially methylated CpGs (Additional file 1: Table S4) on the training (TCGA) set (Additional file 1: Table S1) identified a set of 14 CpGs to distinguish IDH mutant with 1p/19q codeletion (designated as oligodendroglioma) from LGG IDH mutant with intact 1p/19q loci (designated as diffuse astrocytoma) at a threshold value of 9.491 with minimal error (Fig. 5a, Additional file 2: Figure S1B).