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Test Code LAB2281 Thiopurine Metabolites, Whole Blood

Additional Codes

THIO


Ordering Guidance


This specimen cannot be shared with testing for tacrolimus, cyclosporine, sirolimus or everolimus. Testing for these must be ordered separately and separate specimens submitted.



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.


Secondary ID

65381

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 determination of thiopurine metabolite values by liquid chromatography tandem mass spectrometry. Values are utilized to calculate and report the final results (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

-TPMT Testing in the Treatment of Inflammatory Bowel Disease Algorithm

Method Name

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

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
Medical University of South Carolina Note:

On-campus collections: Tube to 99 or deliver to University Extension Hospital Room EH318 

Off-campus collections: 
DO NOT SPIN! DO NOT SHARE!
Specimen to be stored/transported Refrigerated

Reject Due To

Gross hemolysis Reject
Moderate hemolysis Reject
Gross lipemia OK
Gross icterus OK
Clotted Reject

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

Interpretation

Target 6-thioguanine concentrations are 235 to 450 pmol/8x10(8) red blood cell (RBC) with lower levels suggesting suboptimal dosing and higher levels associated with increased risk of myelotoxicity and leukopenia. High 6-methylmercaptopurine levels (greater than 5700 pmol/8x10[8] RBC) suggest an increased risk for hepatotoxicity and potentially "thiopurine hypermethylation."

Method Description

Red blood cell count is first performed and then the thiopurine metabolites values are determined by mass spectrometry.(Unpublished Mayo Method)

Day(s) Performed

Monday, Wednesday, Friday

Report Available

2 to 4 days

Specimen Retention Time

14 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

CPT Code Information

80299

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

Forms

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