26570 Thiopurine Metabolites, Whole Blood (THIO)

​​Thiopurine, Purinethol, Mercaptopurine, 6-MP, 6MP, 6-Thioguanine, Thioguanine, 6-TGN, 6-TG, 6TGN, 6TG, 6-Methylmercaptopurine, Methylmercaptopurine, 6-MMP, 6-MMPN, 6MMPN, 6MMP, Purine antimetabolites, THIO, TPRBC, Thiopurine Metabolites, 6-Mercaptopurine, FPMET​

​​6-Thioguanine Nucleotides

6-Methylmercaptopurine

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

Specimen must be shipped refrigerated.​

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

Gross or moderate hemolysis, and clotted specimens.

​This test cannot be used to predict optimal starting dose. It is sensitive to hemolysis and transport conditions. This test does not replace monitoring of patients using other laboratory tests (eg, complete blood cell count, liver function tests).

​This test is primarily used to verify compliance, optimize therapy, and identify elevated metabolite concentrations that may result in toxicity after initiation of thiopurine drug therapy for the treatment of inflammatory bowel disease. Recommended time points for monitoring include: 4 weeks after starting treatment to verify patient compliance and look for early risk of toxicity; 12 to 16 weeks after starting therapy when 6-thioguanine nucleotides have reached steady-state; and annually.(1) It may also be ordered in patients who do not respond to therapy as expected or as needed for dose changes, flare-ups, signs of toxicity, or suspicion of noncompliance. The test will measure 6-methylmercaptopurine and 6-thioguanine nucleotides in erythrocytes.

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 

​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."