Detection of IDH1 and TERT promoter mutations with droplet digital PCR in diffuse gliomas

Mutations in isocitrate dehydrogenase (IDH) and telomerase reverse transcriptase promoter (TERTp) exert a far-reaching influence on clinicopathologic diagnosis and prognosis of glioma. Traditional approaches, such as Sanger sequencing and ARMS, lack sensitivity due to tumor heterogeneity and low tumor purity of glioma samples. Therefore, we propose a highly sensitive detection method for IDH1 and TERTp mutations based on ddPCR technology, named IDH1-TERT-mutation ddPCR (IT-ddPCR). We determined the IDH1 and TERTp mutations of 80 patients by Sanger sequencing, ARMS, and IT-ddPCR in parallel. We detected the TERTp mutations of 8 patients with probes by IT-ddPCR and Bio-Rad. IDH1-positive singles were detected in 56 cases by IT-ddPCR. TERTp-positive singles were detected in 50 cases by IT-ddPCR. There was a slight difference in total events, occupancy events, and C228T/C250T droplets between these two different probes. Regression analysis of the TERTp variant frequencies detected by probes of IT-ddPCR and Bio-Rad produced a slope of 1.0425 and a coefficient (R²) of 0.9231. We found that IT-ddPCR showed a higher sensitivity compared with Sanger sequencing and ARMS in the detection of IDH1 and TERTp mutations. There were no significant differences in variant frequencies of TERTp mutations between the two probes of IT-ddPCR and Bio-Rad. Thus, IT-ddPCR can be used to detect low-frequency mutation of IDH1 and TERTp in glioma.