IDH1 and glioblastoma: Our study confirms that the T2/FLAIR-mismatch sign is a highly specific but relatively insensitive imaging biomarker for identifying IDH-mutant (1p/19q non-codeleted) lower-grade gliomas from standard anatomical MRI with a high interrater agreement.5,6,10,11 In contrast to previous studies, however, we did not only focus on lower-grade gliomas but also investigated the applicability of the T2/FLAIR mismatch in an unselected cohort of patients with glioma that includes both lower-grade glioma and glioblastoma cases.