Richtlinie: Labormedizinische diagnostik bei der therapie mit TPMT (thiopurin-s-methyltransferase)-abhängigen pharmaka

Thiopurines (azathioprine, 6-mercaptopurine, 6-thioguanine) are widely used as immunosuppressive agents in a variety of diseases. Patients completely deficient in thiopurine S-methyltransferase (TPMT) activity regularly exhibit serious toxicity, mainly hematological cytopenias. For this reason, complete TPMT-deficiency must be excluded prior to thiopurine treatment. This can be achieved either by measuring TPMT-activity in erythrocytes (TPMT-phenotyping) or by genotyping TPMT alleles. Observing the applicable limitations, both methods can be used alternatively. Complex diagnostic findings obtained with one method, however, have to be verified by the alternative method, respectively (genotyping/phenotyping).