Thiopurine methyltransferase - red cells
Last updated: Tuesday, 30, March, 2004
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5 mL blood in lithium heparin or EDTA tube.
Radiometric enzyme assay.
| Reference Interval|
Check with laboratory. Typically, 0.5-0.9 U/g Hb.
Identification of patients at risk of potentially fatal myelosuppression from usual doses of thiopurines (eg, azathioprine, 6-mercaptopurine, thioguanine).
All patients should be assessed prior to commencement of the drug, not retrospectively to ascertain the cause of an adverse reaction.
Approximately 0.3% of the population has a profound genetic deficiency of thiopurine methyltransferase, the major route for detoxification of thiopurines used in immunosuppression and oncology.
Krynetski EY. Pharmacogenetics 1996; 6: 279-290.