IDH1 and glioma: However, routine IHC testing for IDH mutation is only sensitive to the common IDH1 mutation,7 whereas Raman spectroscopy measures the downstream biological consequences of the mutation, most likely associated with the intratumor accumulation of 2-hydroxyglutarate, which is common to all glioma-associated IDH1 and IDH2 mutations.50 In our study, the IHC test for the common IDH1-R132H mutation was, as expected, negative in those cases harboring rare IDH1 or IDH2 mutations (Table 3).