Thiopurine Methyltransferase Activity Profile, Erythrocytes, Mayo, RefLab
Alternate Names
TPMT, Azathioprine toxicity, Imuran toxicity, Mercaptopurine (6-MP) toxicity, Purinethol toxicity, Thioguanine (6-TG) toxicity, Thiopurine resistance
SoftLab Order Code
TPMT3
Epic Order Name
Thiopurine Methyltransferase Activity Profile, Erythrocytes, Mayo, RefLab
Epic Order ID
LAB4407
Laboratory
Reference Lab
Sample Type
Whole Blood
Collection Container
Lavender (EDTA)
Alternative Collection Container
Green top (sodium or lithium heparin)
Collecting Volume
5.0 mL
Minimum Collecting Volume
3.0 mL
Storage or Stability
Refrigerated
Patient Preparation
Thiopurine methyltransferase (TPMT) enzyme activity can be inhibited by several drugs and may contribute to falsely low results. Patients should abstain from the following drugs for at least 48 hours prior to TPMT testing: naproxen (Aleve), ibuprofen (Advil, Motrin), ketoprofen (Orudis), furosemide (Lasix), sulfasalazine (Azulfidine), mesalamine (Asacol), olsalazine (Dipentum), mefenamic acid (Ponstel), trimethoprim (Proloprim), methotrexate, thiazide diuretics, and benzoic acid inhibitors.