TPMT Activity

Also listed as: tp, total protein
Primary unit: Units/mL RBC
LOINC codes: 21563-2
Tests that measure TPMT Activity: Labcorp 1, Quest Diagnostics 1

Ranges

Each lab publishes a reference range for the population groups it tests, usually the middle 95% of results. These intervals describe that population, not an optimal or healthy target. How ranges differ

Quest Diagnostics, TPMT Activity 18831

Population	Interval
>12	Normal metabolizer
4-12	Intermediate metabolizer
<4	Poor metabolizer

Quest Diagnostics test catalog, 18831

Tests

Check the catalog code, specimen, method and preparation for every test that measures TPMT Activity. Select up to five tests to compare them side by side.

Labcorp 1 test

Single-analyte tests

Thiopurine Methyltransferase (TPMT), Enzyme Activity, Erythrocytes 510750
Blood · Fasting not stated · Turnaround 7 - 12 days
Method and collection
Method
Enzymatic endpoint/liquid chromatography/tandem mass spectrometry (LC/MS-MS)
Reference notes
• 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
Labcorp catalog page

Quest Diagnostics 1 test

Single-analyte tests

TPMT Activity 18831
Blood · Fasting not stated · Turnaround Set up: Sun-Thrus (p.m.); Report available: 5-7 days
Method and collection
Method
Chromatography/Mass Spectrometry
Collection
Collect venous blood in 2 separate EDTA (lavender-top) tubes (4 mL in each tube). Ship at 2-8° C (refrigerated) within 24 hours of collection. 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.
Quest Diagnostics catalog page

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Sources

Labcorp test catalog
1 test: codes, specimens, methods, preparation and reference intervals.
Quest Diagnostics test catalog
1 test: codes, specimens, methods, preparation and reference intervals.
LOINC 21563-2
Regenstrief Institute codes that identify the same result across labs.
Search ClinicalTrials.gov for TPMT Activity
Registered studies that measure TPMT Activity, on the U.S. National Library of Medicine registry.

Verify these ranges and sources

We compile this page from named laboratory catalogs, guidelines and studies. Labs calculate reference intervals from the people they test, for one assay method and one population group, so an interval describes that population rather than an optimal target.

Interpret your own results with a licensed clinician, or track your lab history and health goals in Aumnivida.

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