Safe Treatment of IBD Patients with Thiopurines: TPMT Genotyping and Phenotyping

Thiopurine methyltransferase (TPMT) testing is important in the detection of individuals with altered TPMT activity who are at risk for severe hematopoietic toxicity when taking thiopurine medications (6-mercaptopurine, azathioprine, and 6-thioguanine). This webinar will outline the different tests to detect patients who are at risk for thiopurine-related toxicity and the advantages of each test. It is intended to educate clinicians and increase their confidence when treating patients with thiopurine medications.

Learning Objectives

This webinar is intended to educate clinicians and increase their confidence regarding the use of TPMT treatments with patients. The webinar will help you to:

  • Differentiate between TPMT genotyping and phenotyping tests for thiopurine toxicity and determine when to order.
  • Interpret the genotyping, phenotyping, or thiopurine metabolite test results with specific attention to Mayo Clinic’s new three-analyte TPMT phenotype test.
  • Recognize NUDT15 as an additional contributor to thiopurine metabolism and the role of NUDT15 in thiopurine toxicity.
  • Gain confidence in avoiding patient toxicity when ordering thiopurines as a treatment for IBD.

Intended Audience

Clinicians who see IBD patients: gastroenterologists, hepatologists, primary care internal medicine, family medicine, nurse practitioners, physician assistants, laboratory directors, lab supervisors, and laboratory sendout managers.


Ann Moyer, M.D., Ph.D.
Molecular Genetic Pathologist
Mayo Clinic, Rochester, Minnesota

Piero Rinaldo, M.D., Ph.D.
Co-Director, Biochemical Genetics Laboratory
Mayo Clinic, Rochester, Minnesota

Mayo Medical Laboratories is not an applicable manufacturer or applicable group purchasing organization (GPO). GPOs per the Centers for Medicare & Medicaid Services, and this program, do not trigger any reporting requirements pursuant to Open Payments (Sunshine Act) legislation.

Learn more about our testing

MCL Education (@mmledu)

MCL Education

This post was developed by our Education and Technical Publications Team.