Thiopurine Methyltransferase (TPMT), RBC

Abbrev Code:TPMT   
Order Code:LAB6987Order Name:Thiopurine Methyltransferase, RBC
Synonyms:Thiopurine Methyltransferase (TPMT) Enzyme Activity Level; 6-Mercaptopurine
Methodology:Enzymatic/Liquid chromatography/Tandem mass spectrometry
CPT Codes: 84433 x1, 84433 x1
Turnaround Time:Specimens are sent to the reference laboratory Mon-Sat; results are reported within 3-5 days.

For tests developed and validated by ARUP (previously referred to as Compliance Statement B, C or D). This test was developed and its performance characteristics determined by ARUP Laboratories. It has not been cleared or approved by the U.S. Food and Drug Administration. This test was performed in a CLIA certified laboratory and is intended for clinical purposes.

Collection Instructions

Specimen:Whole Blood
Optimal Volume:5 mL
Minimum\Peds Volume:3 mL
Container:Purple (EDTA)
Alternate Containers: Green (sodium heparin, no gel)
Collection Instructions:Refrigerate within 3 hours of collection.
Causes for Rejection:Gel separator tube. Specimens collected in sodium fluoride/potassium oxalate (gray) tube. Hemolyzed, frozen or room temperature specimens.

Processing and Shipping

Specimen Processing:Do not process. Whole blood. Store in refrigerator. Do not freeze.
Shipping Instructions:Ship at refrigerated temperature.
Stability:3 hours at room temperature; 6 days refrigerated.
Test Performed at or Referral Lab Lab Sendouts  (ARUP)
Referral Lab number:92066


Reference Range:

Low TPMT Activity

Less than 17.0 U/mL

Intermediate TPMT Activity

17.0-23.9 U/mL

Normal TPMT Activity

24.0-44.0 U/mL

High TMT Activity

Greater than 44.0 U/mL



Use:Phenotype test to assess risk for severe myelosuppression with standard dosing of thiopurine drugs. Can also detect rapid metabolizer phenotype. Must be performed before thiopurine therapy is initiated.

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