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Thiopurine Methyltransferase Activity

Item Value
Available Stat? No
Test code TPMTA
Performed by Quest
Sendout? Yes
Method LC/MS/MS
Collection Instructions NOTE: Two (2) separate lavender top tubes are required for testing. Preferred to have 4 mL in each tube. Minimum sample volumewould be 2 mL in each tube.
Container type Lavender top x2
Amount to Collect 8 ml blood
Sample type EDTA whole blood
Preferred volume 8 mL blood (4 mL in EACH tube)
Min. Volume 4 mL blood (2 mL in EACH tube)
UCSF Rejection Criteria Clotted or hemolyzed samples.
Processing notes Refrigerate samples (Do NOT freeze) and ship refrigerated to China Basin. Quest test order code is #18831
Ref Lab Rejection Criteria Frozen samples. Clotted or hemolyzed samples
Units 6 -MMP/hr/mL RBC
Normal range
Synonyms TMPT enzyme
Stability Room temperature 2 days, refrigerated 6 days.
Additional information Testing is used to prevent hepatotoxicity from thiopurine therapy. This test can 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.
CPT coding 83789-90
LOINC code 21563-2
Last Updated 9/20/2017 9:44:23 AM
Entry Number 1627
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