Thiopurine S-Methyltransferase Testing Prior to Prescribing Thiopurines

Many experts in inflammatory bowel disease recommend testing thiopurine S-methyltransferase (TPMT) activity before initiating treatment with thiopurines, a recommendation backed by the U.S. Food and Drug Administration. However, there is little evidence on the usefulness of testing.

To investigate whether TPMT testing influences patient management or predicts thiopurine toxicity, and to compare performance of TPMT genotyping with standard enzymatic assaying (phenotyping), researchers conducted a systematic literature review. They found 55 studies that addressed at least one of these research questions.

Regarding the influence of knowledge of TPMT status on patient management, one of two studies, a randomized controlled trial, showed that pati…