The invention belongs to the technical field of
bioinformatics, and particularly relates to a method for detecting abnormal
DNA methylation fragments from
cell free DNA (
cell free DNA, cfDNA) and classifying the abnormal
DNA methylation fragments from the
cell free DNA, and the method comprises the following steps: based on a healthy cfDNA sample and a tumor cfDNA sample, selecting
methylation haplotype regions (
Methylation Haplotype Block, MHB) having
significant difference between the two samples by adopting seven
DNA methylation measurement indexes; on the basis of the selected methylated
haplotype regions with significant differences, constructing total distribution of seven
DNA methylation measurement indexes in the healthy cfDNA sample and the tumor cfDNA sample, and carrying out
differential analysis; seven
DNA methylation measurement indexes are adopted to construct classification models for abnormal
DNA methylation fragments, and the classification models of the seven abnormal DNA methylation fragments are integrated on the basis of
differential analysis results of overall distribution of the seven DNA methylation measurement indexes. According to the application, the abnormal DNA methylation fragments in the
cell free DNA are detected by adopting seven DNA methylation measurement indexes, and the abnormal DNA methylation fragment classification model based on the seven DNA methylation measurement indexes is integrated, so that the improvement of the sensitivity of tumor early screening is facilitated.