TPMT Activity : 18831

Test Code

THIOMR 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.

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

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

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.