<i>TPMT</i> and <i>NUDT15</i> genotyping, TPMT enzyme activity and metabolite determination for thiopurines therapy: a reference laboratory experience

Adding <i>NUDT15</i> to <i>TPMT</i> genotyping, identified additional 3.9% patients to benefit from thiopurine dose modifications. A significant correlation between genetic variants in <i>TPMT</i> and TPMT enzyme levels and between age and enzyme levels was established, while no correlation was identified between sex and enzyme levels nor between <i>TPMT</i> variation and thiopurine metabolites. Providers rely more significantly on genotyping only approach, rather than genotyping and phenotyping.