A Practical Non-Extraction Direct Liquid Chromatography Method for Determination of Thiopurine S-Methyltransferase Activity in Inflammatory Bowel Disease

Thiopurine drugs remain pivotal therapies for the wide varieties of diseases such as inflammatory bowel disease (IBD). Here, thiopurine S-methyltransferase (TPMT) phenotype, the main metabolizing enzyme of thiopurine-drugs, was studied. This is for the first time that TPMT activity is measured in Iranian IBD patients. We used an improved direct liquid chromatography assay without need for solvent extraction and minimize excess labor handling making it ideal for use in routine referral medical centers. TPMT activity in whole blood was determined by a non-extraction HPLC method. We evaluated 427 individuals including 215 IBD patients and 212 unrelated healthy individuals as control group from Iran's western population. TPMT phenotyping of this study demonstrated no frequency for deficient, 2.8 % for low and 97.2% for normal activity, which is different with results of other studies. There was a significant negative correlation between TPMT activities as calculated based on nmol/grHb/h and the Hb-levels in IBD and control groups (r= -0.54, P