Published Jan 23, 2014

Manchester, United Kingdom - Pharmacogenetic testing opens up the potential to personalize medicine. By using patient’s genetic information, clinicians can target medicines towards those who are most likely to benefit, promising better outcomes. An example of a pharmacogenetic test that has made the transition from research into clinical practice is the thiopurine-methyl transferase (TPMT) test. A small percentage of patients being treated with azathioprine for autoimmune conditions, such as Crohn’s disease and rheumatoid arthritis, are at risk of developing life-threatening adverse drug reactions (ADRs). TPMT genotyping can potentially identify those patients who are at increased risk of serious infection, allowing clinicians to alter treatment accordingly. Previous model-based studies showed TPMT testing to be cost-effective, however, no assessment has been conducted which uses robust evidence from a randomized controlled trial. Researchers from The University of Manchester and The University of Nottingham evaluated the cost-effectiveness of a TPMT genotyping test to inform azathioprine prescribing in autoimmune diseases. They calculated the incremental costs and quality-adjusted-life-years QALYs associated with the test by conducting an economic evaluation alongside a pragmatic randomized controlled trial in the North West of England. Patients in the genotyping-test group used fewer health care resources than those in the no-test group but they also gained slightly fewer QALYs. There was no difference found in the number of ADRs experienced by patients in either trial group. The results showed that TPMT genotyping is potentially cost-saving but a great deal of uncertainty exists on the tests overall utility. The study also highlights the increased methodological complexities involved in conducting a pragmatic trial for a pharmacogenetic test. Lead author Alex Thompson, MSc, a health economist from The Manchester Centre for Health Economics said: “Our analysis should be of interest to policy makers, health care providers and future researchers. Whilst pharmacogenetic testing offers great potential to personalize medicine, decision makers require robust evidence on patient outcomes and resource-use sourced from appropriate randomized controlled trials. Our results provide some evidence on these attributes for TPMT genotyping but a great deal of uncertainty remains. We provide recommendations for future researchers who are planning trial-based evaluations of pharmacogenetic tests.”  The full study, “The Cost-Effectiveness of a Pharmacogenetic Test: A Trial-Based Evaluation of TPMT Genotyping for Azathioprine,” is published in Value in Health.

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