Building on this concept, Ono et al. (1996) used multiplex PCR to assess CDKN2A/B HD in 50 astrocytomas and found a positive correlation between the Ki-67 index and CDKN2A HD (5/20 grade 3 astrocytomas and 6/13 glioblastomas had CDKN2A HD). This evidence concerns the gene CDKN2A and astrocytoma (excluding glioblastoma).