Cost‐effectiveness of thiopurine methyltransferase genotype screening in patients about to commence azathioprine therapy for treatment of inflammatory bowel disease

• Published in: Alimentary pharmacology & therapeutics Vol. 20; no. 6; pp. 593 - 599
• Main Authors: Winter, J., Walker, A., Shapiro, D., Gaffney, D., Spooner, R. J., Mills, P. R.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 15.09.2004; Blackwell
• Subjects: Adult; Azathioprine - economics; Azathioprine - therapeutic use; Biological and medical sciences; Cost of Illness; Cost Savings; Cost-Benefit Analysis; Digestive system; Gastroenterology. Liver. Pancreas. Abdomen; Genetic Testing - economics; Genetic Testing - methods; Genotype; Heterozygote; Homozygote; Humans; Immunosuppressive Agents - economics; Immunosuppressive Agents - therapeutic use; Inflammatory Bowel Diseases - drug therapy; Inflammatory Bowel Diseases - economics; Inflammatory Bowel Diseases - genetics; Medical sciences; Methyltransferases - genetics; Middle Aged; Pharmacology. Drug treatments; Polymorphism, Genetic - genetics; Human; Enzyme; Transferases; Genotype; Inflammatory disease; Treatment; Methyltransferases; Health economy; Thiopurine S-methyltransferase; Immunosuppressive agent; Azathioprine; Public health; Cost efficiency analysis
• ISSN: 0269-2813; 1365-2036
• DOI: 10.1111/j.1365-2036.2004.02124.x

Summary Background : Azathioprine is a useful agent in the management of inflammatory bowel disease. Its use is limited by its side‐effect profile. Marrow toxicity occurs in approximately 3.2% of patients and is known to be associated with diminished thiopurine methyltransferase enzyme activity resulting from genetic polymorphisms. Aim : To evaluate the cost‐effectiveness of screening for thiopurine methyltransferase gene polymorphisms prior to initiation of azathioprine therapy. Methods : Analysis of the literature was undertaken to calculate the expected frequency of leucopenia and its relationship with thiopurine methyltransferase polymorphisms in a model of theoretical inflammatory bowel disease patients. Decision analysis was then applied to assess the cost of a pre‐treatment genotyping strategy, taking account of direct costs and cost per life‐year saved. Results : In 1000 inflammatory bowel disease patients treated with azathioprine, 32 will develop myelosuppression and one will die because of this. Of those who develop myelosuppression during azathioprine therapy, 32% are attributable to lower thiopurine methyltransferase activity. Pre‐treatment genotyping costs £347 per life‐year saved for a 30 year old and £817 per life‐year saved for a 60 year old. This compares favourably with other health care technologies. Conclusion : The use of pre‐treatment screening for thiopurine methyltransferase polymorphisms in inflammatory bowel disease patients commencing azathioprine therapy represents good value for money.