Is CYP2D6 phenotype predictable from CYP2D6 genotype?

In conclusion, CYP2D6 genotyping for the most frequent allelic variants was able to reliably predict CYP2D6 phenotypes in most donors; however, the external factors modifying the phenotypic appearance of CYP2D6 had to be taken into account. Personalized medication strategy should include monitoring of CYP2D6 genotype in a more comprehensive manner and should take external factors into consideration for an appropriate prediction of CYP2D6 metabolizing capacity.