TPMT Testing in Treatment of Inflammatory Bowel Disease [Test in Focus]

Video Overview

Available Tests

When to Order

Algorithm

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Why is TPMT Testing Important?

• Detection of individuals with low thiopurine methyltransferase (TPMT) activity who are at risk for excessive myelosuppression or severe hematopoietic toxicity when taking thiopurine drugs.
• Detection of individuals with hyperactive TPMT activity who have therapeutic resistance to thiopurine drugs and may develop hepatotoxicity if treated with these drugs.

Available Tests and Advantages of Each

• TPNUV — Thiopurine Methyltransferase (TPMT) and Nudix Hydrolase (NUDT15) Genotyping
  Advantages:
  • Can identify patients at risk of toxicity and start them on a reduced dose or alternate therapy
  • Test is not impacted by other medications
  • DNA is stable/specimen is less sensitive to transport conditions
  • Includes NUDT15 (three genetic variants)
• TPMT3 — Thiopurine Methyltransferase (TPMT) Activity Profile, Erythrocytes
  Advantages:
  • Can identify patients at risk of toxicity and start them on a reduced dose or alternate therapy
  • Can also detect hyperactive metabolizer
• THIO — Thiopurine Metabolites, Whole Blood
  Advantages:
  • Can adjust/optimize dose during course of therapy
  • Can monitor impact of additional drugs (i.e. allopurinol) added during course of therapy

When to Order (click to enlarge)

Algorithm (click to view PDF)

Mayo Clinic Laboratories

This post was authored by the Marketing Team at Mayo Clinic Laboratories.