Distinct patterns of DNAm within CpG classification systems. Probes were grouped into three levels of DNAm based on average ß values within a tissue: hypomethylated (ß values of 0 to ≤0.2, yellow), heterogeneously methylated (ß values of >0.2 to <0.8, light blue) and hypermethylated (ß values of ≥0.8 to 1, dark blue). The percentage of probes in Illumina and HIL-annotated CpG classes was plotted for the three levels of DNAm in blood (n = 4). HIL CpG classes were more characteristic in their DNAm profiles than Illumina-annotated CpG classes. Numbers on top of bars indicate number of probes/class. DNAm, DNA methylation; HIL, high-density CpG island (HC), intermediate-density CpG island (IC) and non-island (LC); ICshore, intermediate-density CpG island shore.