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Test ID THIO Thiopurine Metabolites, Whole Blood

Shipping Instructions

Specimen must be shipped refrigerated.

Specimen Required

Container/Tube: Lavender top (EDTA)

Specimen Volume: 3 mL

Collection Instructions: Send whole blood specimen in original tube. Do not aliquot, centrifuge, or freeze.

Useful For

Aids physicians in dose adjustments, minimizing dose-dependent toxicity, and monitoring compliance of thiopurine drug therapy

Testing Algorithm

A red blood cell (RBC) count is performed followed by determined of thiopurine metabolite values by liquid chromatography-tandem mass spectrometry. Values are utilized to calculate and report a final result (unit of measure: pmol/8 x 10[8] RBC) for 6-thioguanine nucleotides and 6-methylmercaptopurine derivative analyte.


For more information see Ulcerative Colitis and Crohn Disease Therapeutic Drug Monitoring Algorithm.

Method Name

Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)

Reporting Name

Thiopurine Metabolites, B

Specimen Type

Whole Blood EDTA

Specimen Minimum Volume

1.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Whole Blood EDTA Refrigerated (preferred) 8 days
  Ambient  24 hours

Reference Values

6-Thioguanine Nucleotides (6-TGN): 235-450 pmol/8x10(8) red blood cell (RBC)

6-Methylmercaptopurine (6-MMP): Less than or equal to 5700 pmol/8x10(8) RBC

Day(s) Performed

Monday through Friday

Report Available

2 to 4 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
THIO Thiopurine Metabolites, B 82869-9


Result ID Test Result Name Result LOINC Value
49580 6-Thioguanine Nucleotides 32660-3
49581 6-Methylmercaptopurine 32654-6


If not ordering electronically, complete, print, and send Gastroenterology and Hepatology Client Test Request (T728) with the specimen