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| A B C D E F G H I J K L M N O P Q R S T U V W X Y Z # |
Thiopurine Metabolites
Test Code91745
CPT Codes
80299
Includes
6-Thioguanine (6-TG) and 6-Methylmercaptopurine (6-MMP)
Preferred Specimen
5 mL whole blood collected in an EDTA (lavender-top) tube
Patient Preparation
A trough specimen is required (within 1 hour prior to the next dose).
Minimum Volume
2.5 mL
Transport Temperature
Refrigerated (cold packs)
Specimen Stability
Room temperature: 24 hours
Refrigerated: 7 days
Frozen: Unacceptable
Refrigerated: 7 days
Frozen: Unacceptable
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Heparin whole blood • Frozen • Hemolysis
Methodology
Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS)
FDA Status
This test was developed and its analytical performance characteristics have been determined by Quest Diagnostics. It has not been cleared or approved by the FDA. This assay has been validated pursuant to the CLIA regulations and is used for clinical purposes.
Setup Schedule
Set up: Tues-Sat; Report available: 3-5 days
Reference Range
| 6-TG | 235-400 pmol/8x10(8) RBC |
| 6-MMP | <5700 pmol/8x10(8) RBC |
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.
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.
