Test Code Billings Clinic: 4836 Prometheus: 3320 TPMT Enzyme
Performing Laboratory
Prometheus Laboratories, Inc.
Useful For
PROMETHEUS® TPMT Enzyme testing provides a quantitative analysis of a patient’s thiopurine methyltransferase (TPMT) enzyme activity level. Because each patient metabolizes thiopurines differently, the efficacy and toxicity of thiopurines can vary widely from patient to patient. Knowledge of the TPMT enzyme phenotype may reduce time of response, allow physicians to individualize dosing, identify patients in whom thiopurine therapy should be avoided and help reduce the risk of leukopenia.
Methodology
High Pressure Liquid Chromatography (HPLC)
Specimen Requirements
- Draw blood in a lavender-top (EDTA) tube(s)
- Send 5 mL of unprocessed EDTA whole blood refrigerated.
- Do not centrifuge.
- Do not freeze.
- Forward unprocessed whole blood promptly.
Reference Values
Normal TPMT Activity:
>21.0 EU/mL
Intermediate TPMT Activity:
6.0-21.0 EU/mL
Low TPMT Activity:
<6.0 EU/mL
Day(s) Test Set Up
Monday through Friday
Test Classification and CPT Coding
82491 - Quantitative HPLC (High Pressure Liquid Chromatography) for 6-methyl-thioguanine
82657 - TPMT (thiopurine S-methyltransferase) enzyme activity in peripheral RBC
This test was developed and its performance characteristics determined by Prometheus Laboratories Inc. It has not been cleared or approved by the U.S. Food and Drug Administration.