Clinics and Departments

Laboratory Services

Lab Dept:


Test Name:


General Information

Lab Order Codes:



Prometheus TPMT Genetics; Thiopurine S-methyltransferase Genetics

CPT Codes:

81401 – Molecular pathology, Level 2

Test Includes:

A qualitative evaluation, to determine a patient’s ability to produce thiopurine methyltransferase enzyme. Classifies patients into one of three genotypes; normal (wild type), heterozygous or homozygous recessive.


Test Indications:

Because each patient metabolizes thiopurines differently, the efficacy and toxicity of thiopurines can vary widely from patient to patient. Knowledge of the TPMT genotype may; reduce time to response, allow physicians to individualize dosing, identify patients in whom thiopurine therapy should be avoided and help reduce risk of leukopenia.

Lab Testing Sections:

Chemistry - Sendouts

Referred to:

Prometheus Therapeutics and Diagnostics (Prometheus Test: 3300)

Phone Numbers:

MIN Lab: 612-813-6280

STP Lab: 651-220-6550

Test Availability:

Daily, 24 hours

Turnaround Time:

1 – 3 days

Special Instructions:



Specimen Type:

Whole blood


Lavender top (EDTA) tube

Draw Volume:

5 mL blood

Processed Volume:

Same as Draw Volume


Routine venipuncture

Special Processing:

Lab Staff: Do Not Centrifuge. Store specimen at ambient temps before shipping. Stable for 8 days at ambient temperatures and 30 days at 2-8 degrees centrigrade.

Use the following procedure with the Coolant Equipped Transportation Kit:

1. Freeze flat the cold pack included in the kit.
2. Only one specimen may be shipped for each cold pack.
3. Use an EDTA vacutainer tube, inverted 2-3 times to mix.
4. Label whole blood specimen with pt name, collect date, date of birth, MR number and lab accession number.
5. Place specimen in zip lock bag along with dry mop.
6. Place tube in tube compartment.
7. Place frozen cold pack in large compartment.
8. Fold and insert the Prometheus copy of the requisition into the remaining compartment.
9. Close the kit, place into the Airborne Biological Specimen Bag and seal. 10. Fill in your return address and adhere the label to the specified location on the Airborne bag.
11. Call Airborne Express at 1-800-247-2676 for pickup.

Patient Preparation:


Sample Rejection:

Mislabeled or unlabeled specimens


Reference Range:

TPMT*1/TPMT*1 – Alleles present are associated with Normal Enzyme Activity

Critical Values:





Isolation/Extraction of nucleic acid, Amplification of nucleic acid for three different DNA sequences, Nucleic acid probe


Prometheus March 2011


3/14/2011: CPT update for testing from Prometheus
11/26/2013: CPT update

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