A comparison of the amount of isolated cfDNA, the %cfDNA score and the detection of DNA methylation of BCAT1 and/or IKZF1 revealed that colorectal cancer samples positive for BCAT1 and/or IKZF1 DNA methylation had a %cfDNA score of at least 23% and an input amount of at least 12 ng isolated cfDNA (8.5 ng cfDNA with fragment size 50–700 bp, adjusted using the %cfDNA score) for bisulfite conversion and ddPCR (Additional file 2: Table S4). Here, IKZF1 is linked to colorectal cancer.