THIOPURINE METHYLTRANSFERASE, ERYTHROCYTES
- THIOPURINE METHYLTRANSFERASE, ERYTHROCYTES
- Start Date
- Expiration Date
- CPT Codes
- Reference Test
- ATLAS Test Code
Lavender top (EDTA), WHOLE BLOOD
- Transport Info
- Fasting Required?
- Patient Instructions
- Reference Range
High Performance Liquid Chromatography (HPLC)
The TPMT, RBC assay is used as a screen to detect individuals with low (abnormal) TPMT activity that may be at risk for excessive myelosuppression when exposed to standard doses of thiopurines such as azathioprine (Imuran) and 6-mercaptopurine (Purinethol). TPMT is the primary metabolic route for inactivation of thiopurine drugs in the bone marrow. When TPMT activity is low, it is predicted that proportionately more 6-mercaptopurine is converted into the cytotoxic 6-thioguanine nucleotides, which will accumulate in the bone marrow and cause excessive toxicity. The activity of TPMT is measured by the nanomoles of 6-methylmercaptopurine (inactive metabolite) produced per 1 mL of packed red blood cells, (U/mL).