Genetic Testing for Thiopurines
At UF Health, clinicians order a TPMT genetic test through the UF Health Precision Medicine Program and UF Health Pathology Laboratories to help determine the right medicine and the right dose to treat adult and pediatric patients with certain types of bowel or joint disorders, such as Crohn’s disease, or to treat pediatric patients with acute lymphoblastic leukemia.
The thiopurines are a family of three medications: azathioprine (Imuran®), mercaptopurine (Purinethol®, 6-MP), and thioguanine (Tabloid®). For thiopurines to work, a protein in the body called TPMT has to help process the medications. This protein works faster or slower depending on a patient’s genetics. If the protein works slower, there may be a higher chance of developing side effects. The U.S. Food and Drug Administration includes a precaution about these genetic factors in thiopurine drug labels.
A TPMT genetic test is usually ordered before starting a thiopurine medication. Additional blood tests may be ordered throughout therapy to monitor drug levels in a patient’s blood cells.
The UF Health Precision Medicine Program collaborated with three clinical services at UF Health to integrate this test as a routine part of inpatient care in February 2014 and outpatient care in June 2014. Clinical leads for the collaboration are: William Slayton, M.D., Kenny Higgins, P.A., and Tara McCabe, Pharm.D., in pediatric hematology and oncology; Christopher Jolley, M.D., and Joan English, P.A., in pediatric gastroenterology; and Sarah Glover, D.O., and Rick Davis, P.A., in adult gastroenterology.