CDO1 and cholangiocarcinoma: As absolute quantification of DNA methylation in samples was possible by ddPCR; Vedeld et al. analyzed 344 bile samples containing CCA and other benign biliary diseases by ddPCR, indicating the sensitivity and specificity of combing diagnosis of CDO1, CNRIP1, SEPT9 and VIM promoter methylation were 100% and 90%, respectively [10].