DNA index was measured by FACS as described in “DNA index, immunophenotyping, molecular analysis of chromosomal abnormalities” and DNA index of 278 ALL samples were available. Normal diploid cells have a DNA index of 1.0. When DNA index is the same as or greater than 1.16, the leukemia is defined as hyperdiploid ALL by DNA index. Hyperdiploid ALL detected by SNP-chip analysis had more than 50 chromosomes, which were counted manually.

HD indicates hyperdiploid ALL; and non-HD, nonhyperdiploid ALL.