Test Name
THIOPURINE METHYLTRANSFERASE (TPMT) ACTIVITY
Aliases
TPMT PHENOTYP; TPMT ACTIVITY; TPMT DEFICIENCY; 6-MERCAPTOPURINE (6-MP; PURINETHOL) TOXICITY; AZATHIOPRINE (IMURAN) TOXICITY.
Abbreviations
TPMT
Test Classification
INDIVIDUAL
Department
SPECIAL CHEMISTRY
Sub Department
-
TAT Category
ELAPSED (CONTINUOUS) TIME
Estimated TAT
7
TAT Units
DAYS
Test Requirements
2ml EDTA plasma or heparin plasma. EDTA or heparin with aliquoting of plasma into a separation vial.
Clinical Utility
To detect thiopurine methyltransferase deficiency prior to initiation of treatment with thiopurine drugs e.g. azathioprine, 6-mercaptopurine (6-MP), 6-thioguanine (6-TG) etc. TPMT deficiency predisposes to myelotoxicity (bone marrow toxicity) from standard doses of thiopurine drugs. Increased TPMT activity may be associated with resistance to thiopurine drugs & increased risk of hepatotoxicity.
Last Review
26th Feb 2026