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
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 RBC) suggest an increased risk for hepatotoxicity and potentially "thiopurine hypermethylation."