Use of thiopurine testing in the management of inflammatory bowel diseases in clinical practice: A worldwide survey of experts

Background: We performed a worldwide survey to evaluate the extent to which gastroenterologists who are experts in the field of inflammatory bowel diseases (IBDs) are utilizing thiopurine metabolism in practice. Methods: This was a Web-based cross-sectional survey consisting of 12 multiple-choice and open-ended questions. Results: Between December 2009 and April 2010, 175 questionnaires were received. The proportion of practitioners with access and reimbursement for thiopurine S-methyltransferase (TPMT) genotype, TPMT phenotype, 6-thioguanine nucleotides (6-TGN) levels, and 6-methylmercaptopurine ribonucleotides (6-MMP) levels was 48%, 54%, 44%, and 35%, respectively. Before azathioprine initiation, TPMT genotype and phenotype were performed by only 30% and 43% of responders, respectively. In patients on thiopurine therapy, 6-TGN and 6-MMP levels were determined by 54% and 44% of responders, respectively. Only 27% of physicians always wait for TMPT activity/genotype results before initiating azathioprine and 81% do not routinely recheck metabolite levels after dose escalation or reduction. In cases of very high or low TPMT activity, 75% and 74% of practitioners take into account TMPT activity result, respectively. If access to all azathioprine metabolite measurements was available and if all these tests were reimbursed by public health insurance, 47% of responders would use these tests more often in their practice. The availability and reimbursement of TPMT status and azathioprine metabolites strongly influenced experts' attitudes. Conclusions: Thiopurine testing is relatively underutilized by IBD gastroenterologists. The availability and reimbursement of TPMT status and azathioprine metabolites strongly influence the management of IBD patients treated with thiopurines.