Thiopurine Metabolites in Red Blood Cells
Also known as: THIOMET
Use
Thiopurine drug therapy is used to treat autoimmune diseases, inflammatory bowel disease, acute lymphoblastic leukemia, and to prevent rejection after solid organ transplant. These drugs are metabolized to active 6-thioguanine nucleotides, regulated by TPMT and NUDT15 enzymes. Variants in TPMT and/or NUDT15 genes can lead to accumulation of cytotoxic metabolites, increasing the risk of drug-related toxicity. Measuring thiopurine metabolite concentrations aids in assessing therapeutic and toxic concentrations.
Special Instructions
For enzyme phenotyping before treatment, refer to TPMT RBC (0092066). For pharmacogenetic testing before or during treatment, refer to TPMT and NUDT15 (3001535). Ensure trough collection is done within 1 hour prior to next dose.
Limitations
This test is not FDA-approved but is performed in a CLIA-certified laboratory. It is intended for clinical purposes but has not undergone FDA clearance. The test evaluates the concentrations of specific thiopurine metabolites but may not account for other factors influencing thiopurine toxicity or efficacy.
New York Approved
Methodology
Mass Spectrometry
Biomarkers
LOINC Codes
- 32660-3
- 32654-6
Result Turnaround Time
1-5 days
Related Documents
For more information, please review the documents below
Specimen
Whole Blood
Volume
5 mL
Minimum Volume
2.5 mL
Container
Lavender (EDTA) or pink (K2EDTA)
Patient Preparation
Trough collection (within 1 hour prior to the next dose).
Storage Instructions
Refrigerated.
Causes for Rejection
Gel separator tubes, hemolyzed or lipemic specimens, frozen specimens.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 24 hours |
| Refrigerated | 7 days |
| Frozen | Unacceptable |
Other tests from different labs that may be relevant