Azathioprine is a useful agent in the management of inflammatory bowel disease (IBD). However, its use is limited by its side-effect profile.
Previously it was shown that marrow toxicity occurs in approximately 3.2% of patients and this is known to be associated with diminished thiopurine methyltransferase enzyme activity resulting from genetic polymorphisms.
Researchers from Glasgow, Scotland carried out a study to evaluate the cost-effectiveness of screening for thiopurine methyltransferase gene polymorphisms prior to initiation of azathioprine therapy.
|Pre-treatment genotyping costs £347 per life-year saved for a 30 year old|
|Alimentary Pharmacology and Therapeutics|
The research group performed a detailed analysis of the literature in order to calculate the expected frequency of leucopenia and its relationship with thiopurine methyltransferase polymorphisms in a model of theoretical IBD patients.
The researchers then assessed the cost of a pre-treatment genotyping strategy, taking account of direct costs and cost per life-year saved.
The team calculated that in 1000 IBD patients treated with azathioprine, 32 will develop myelosuppression and one will die because of this.
In addition, 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.
Dr Winter, speaking on behalf of his colleagues, conlcluded "The use of pre-treatment screening for thiopurine methyltransferase polymorphisms in IBD patients commencing azathioprine therapy represents good value for money."