It is possible that a subject has > 2 DPYD variants and this DPYD_Diplotype_Phenotype_Table is a representation of possible DPYD genotypes considering the two functionally most impacted (lowest activity value) variants. Based on the CPIC guideline for Dihydropyrimidine Dehydrogenase Genotype and Fluoropyrimidine Dosing: 2017 Update (PMID: 29152729), the DPD phenotype is assigned using a gene activity score (DPYD-AS; based on the DPYD Allele Functionality Table), calculated as the sum of the two DPYD variants with the lowest variant activity value. A translation of Allele Function combinations to Phenotype is available in the "DPYD_phenotypes" file. If two decreased/no function variants are present, each decreased/no function variant is considered to be on a different gene copy when the phase is not known.