| Test Name: |
THIOPURINE METABOLITES |
| Test Code: |
2191942 |
| Alias: |
6-Methylmercaptopurine
6-MMP
6-MP
6-TG
6-Thioguanine
91745
AZA
LAB12027
|
| CPT Code(s): |
80299
|
| Test Includes: |
6-Thioguanine (6-TG) and 6-Methylmercaptopurine (6-MMP) |
| Preferred Specimen: |
5 mL whole blood |
| Container: |
EDTA Lavender |
| Minimum Volume: |
2.5 mL whole blood |
| Collection Instructions: |
Invert tube 5 to 10 times immediately after filling to prevent clotting. |
| Transport Temperature: |
Refrigerated |
| Stability: |
Room temperature: 24 hours
Refrigerated: 7 days
Frozen: Unacceptable |
| Rejection Criteria: |
Hemolysis • Heparin whole blood • Received frozen |
| Limitations: |
This test was developed and its analytical performance characteristics have been determined by Quest Diagnostics. It has not been cleared or approved by FDA. This assay has been validated pursuant to the CLIA regulations and is used for clinical purposes |
| Additional Information: |
A trough specimen is required (within 1 hour prior to next dose) |
| Schedule: |
Set Up: Tuesday – Saturday
Report Available: 4-6 days |
| Method: |
Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS) |
| Performing Lab: |
Quest Diagnostics, Wood Dale > MedFusion #91745 |
| Clinical Significance: |
6-Mercaptopurine (Purinethol) and its imidazolyl derivative, Azathioprine (Imuran), are immunosuppressive drugs. 6-Mercaptopurine (6-MP) is indicated for remission induction and maintenance therapy of acute lymphoblastic leukemia (ALL). Azathioprine is indicated as an adjunct for the prevention of rejection in renal allograft (kidney transplant) patients, for the management of rheumatoid arthritis, and for the management of inflammatory bowel disease.
Azathioprine is cleaved to 6-MP. 6-MP is metabolized via a series of enzymatic steps to 6-thioguanine nucleotides (6-TGNs), to 6-methyl-mercaptopurine (6-MMPNs) by the enzyme thiopurine methyltransferase (TPMT), and to 6-thiouric acid by the enzyme xanthine oxidase (XO). TPMT enzyme activity has large inter-individual variations which affect the efficacy, toxicity and variability of the treatment. Therapeutic drug monitoring of 6-MP metabolites (6-TGNs and 6-MMPNs) in erythrocytes is recommended to assist therapy, particularly in combination with TPMT enzyme activity or mutation analysis. |
| Use: |
Updated: 09/25/2025 |
| Reference Ranges: |
6-TG 235-400 pmol/8x10(8) RBC
6-MMP <5700 pmol/8x10(8) RBC |
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The CPT codes included in this publication are in accordance with Current Procedural Terminology, a publication of the American Medical Association. CPT codes are provided here for the convenience of our clients; however, correct coding often varies from one carrier to another, and HealthLab may bill specific carriers using codes other than those shown. Clients who bill for services should verify the code(s) with the applicable payor to confirm that their use is appropriate in each case.
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| Test Type: |
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