Raman spectroscopy for the identification of isocitrate dehydrogenase (IDH) mutated glioblastomas.
Determining IDH status of glioblastomas is critical for histological diagnosis and clinical decision-making. Raman spectroscopy probes the unique molecular vibrations of a sample to accurately characterise its molecular composition. We investigate the feasibility of using Raman spectroscopy to differentiate between IDH1 positive and negative tumours.
Spectroscopic analysis of neuropathological samples.
40 glioblastoma formalin fixed samples classified into either IDH1þ or IDH1- using standard immunohistochemistry IDH1(R132H) stain. 3 additional samples with rare IDH1 mutations (R132G) were also used. Methods: Spectral maps of 1mm2 were acquired from two areas on each sample using a Raman microscope configured with a 785nm excitation laser source. Acquisition time less than 60 minutes per map.
72 spectral maps (145,800 spectra) from 36 samples (18 IDHþ and 18 IDH-) were included in the analysis. 4 hypocellular samples were excluded. Principal component analysis (PCA) demonstrated good separation of the IDH1þ and IDH1- groups. A PCAlinear discriminant analysis classification model demonstrated 97% sensitivity and 90% specificity for predicting the presence of an IDH1 mutation. We also demonstrated similar accuracy when classifying rare IDH1 mutations into the IDH þ group.
Raman spectroscopy can accurately and rapidly distinguish IDH1 mutated glioblastomas from their IDH1 negative counterparts. Further work is currently being undertaken on fresh, intraoperative, tumour samples.
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