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TPMT Activity : 18831
Test CodeTHIOMR or 18831
Alias/See Also
Thiopurine Methyltransferase, RBC
CPT Codes
84433
Instructions
Blood is collected prior to azathioprine (imuran) or 6-mercaptopurine (6-mp, purinethol) therapy for screening purposes. The draw time is at physician's discretion.
Two separate Lavender (EDTA) tubes.
Two separate Lavender (EDTA) tubes.
Transport Container
Transport 2 tubes (4 mL each) whole blood. (Min: 2 tubes (2 mL each))
Transport Temperature
Refrigerated.
Specimen Stability
Ambient: 48 hours; Refrigerated: 9 days; Frozen: Unacceptable
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Hemolysis. Clotted. Animal specimen. Forensic specimen.
Methodology
Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS)
Setup Schedule
Sunday - Thursday
Report Available
4-6 days (From receipt at performing laboratory)
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.
Reference Range
greater than 12 Normal
4-12 Heterozygote or low metabolizer
less than 4 Homozygote Deficient Range
4-12 Heterozygote or low metabolizer
less than 4 Homozygote Deficient Range
Clinical Significance
Help prevent hepatotoxicity from thiopurine therapy. This test helps identify individuals at increased risk of hepatotoxicity from thiopurine dose escalation. Patients with a TMPT activity of 4-12 nmol 6-MMP/hr/mL RBC (heterozygote/low metabolizer) are at increased risk and may require a lower dose of thiopurine drug.
Performing Laboratory
Quest Diagnostics