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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.