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.
Video Overview
Available Tests and Advantages of Each
- TPNUQ — 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