Thiopurine methyltransferase

Alphabetical Test listing

Thiopurine methyltransferase-13556

Test name:

Test number:

13556

Excellian order number:

LAB13556

Abbreviation:

TPMT

Alternate names:

Thiopurine methyltransferase (TPMT), enzyme activity, erythrocytes
TPMT biochemical assay, myelotoxicity

Useful for:

Determination of TPMT levels that may be associated with toxicity of anticancer and anti-inflammatory drugs

Limitations:

For patients having an intrinsic low level of TPMT, recent RBC transfusion can variably increase their assayed enzymatic activity depending on the amount and circulating half-life of the transfused red blood cells.

Specimen type:

Sodium heparin (Na hep) whole blood

Collection container:

Dk green Sodium heparin (Na hep), no gel - 10mL

Volume:

8 mL

Minimum volume:

5 mL

Collection instructions:

Immediately following collection, mix sample thoroughly by gently inverting 8 - 10 times, to prevent clotting

Transport container:

Dk green Sodium heparin (Na hep), no gel - 10mL

Alternate specimen type:

EDTA whole blood

Alternate collection container:

Lavender (EDTA), 10mL

Alternate collection instructions:

Immediately following collection, mix sample thoroughly by gently inverting 8 - 10 times, to prevent clotting

Alternate transport container:

Lavender (EDTA), 10mL

Transport and stability:

Refrigerated (strict) - 14 days

Frozen - NO

Reason for rejection:

Frozen specimen
Gross hemolysis
Clotted specimen

Performing lab:

Esoterix Endocrinology (501792) via LabCorp (510750): R-LC

Days set up:

3x per week

TAT:

10-12 days

Method:

Enzymatic endpoint/liquid chromatography/tandem mass spectrometry (LC/MS-MS)

Reference ranges:

Normal: 15.1 - 26.4 units/mL RBC

Heterozygous for low TPMT variant: 6.3 - 15.0 units/mL RBC

Homozygous for low TPMT variant: <6.3 units/mL RBC

CPT codes:

84433

LOINC code:

Result 21563-2

Date created:

04/11/2019

Revised date:

01/01/2023

Review date:

12/20/2023