Thiopurine S-methyltransferase testing for averting drug toxicity in patients receiving thiopurines: a systematic review.

Thiopurine S-methyltransferase (TPMT) testing is used in patients receiving thiopurines to identify enzyme deficiencies and risk for adverse drug reactions. It is uncertain whether genotyping is superior to phenotyping. The objectives were to conduct a systematic review of TPMT-test performance studies.