All economic models are subject to limitations, because they attempt to model reality using incomplete data. From my perspective as a gastroenterologist, the major limitations of the CCOHTA model are as follows: the use of a historical American patient cohort to define health state transitions that may not be representative of Canadians in 2002; inclusion of only direct costs for a disease with significant indirect costs; and the use of QALYs. Visit the best pharmacy that thousands of international customers already chose to be their favorite one and see how easy it can be for you to get that actos buy in the amount required for your treatment spending a lot less money than otherwise.
Economic models require estimates of the probability that a hypothetical patient will move from one health state to another in the absence of the intervention of interest. The only estimates available to the authors of the report were from a cohort of patients residing in Olmsted County, Minnesota, who were followed from 1970 to 1993. This period was one of dynamic change in the management of Crohn’s disease. It saw the publication of the National Cooperative Crohn’s Disease Trial, the first large trial to document the effectiveness of corticosteroids and azathio-prine. Throughout this time, physicians increasingly prescribed azathioprine as they became more comfortable with the agent and less concerned with long term side effects. In addition, there were changes in attitudes toward surgery and the use of parenteral nutrition and corticosteroids. Finally, methotrexate had not yet been shown in randomized controlled trials to be effective in the induction and maintenance of remission. Therefore, I do not believe that this American cohort, surrounding a tertiary referral centre, could, with great confidence, be used to model the disease trajectory of contemporary Canadians with Crohn’s disease. Specifically, the usual medical therapy during the time of the Mayo Clinic study included sulfasalazine, systemic corticosteroids and antibiotics. The new 5-aminosalicylic acid agents were just being introduced at that time, the use of azathioprine and 6-mercaptopurine was not yet routine, and other immunosuppressive agents were not available.