Resumen de Economic evaluation in health research: cohort simultation and applications
Nuria Perez Alvarez 
Currently, resources that may be spent in health care are limited so it is necessary to rationalize their consumption and prioritise their allocation to the options with higher health outcome and economic sustainability. It is for that reason that economic analyses are increasingly included in medicine research as an instrument for evaluating different therapeutic strategies. In this thesis, both cost and health outcome are separately and jointly evaluated to compare different therapeutic strategies to treat diseases in different and specific health areas. The challenge was adapting and implementing the methods to reflect the assessed health issue. The analyses require data, and the main sources to obtain them are clinical studies (prospective or retrospective), or simulation models. The use of simulations avoids to experiment directly to the system of interest, these methods imply a smaller time consumption and cost, and any danger can be caused by the experimentation performance. However, the simulated data always is going to be an approximation of real data. Real data of a clinical trial was used in the assessment of the adherence to antiretroviral treatment promotion program in HIV infected patients. A decision tree was used to study the cost per health gain, measured by means of clinical and health related quality of life outcomes. The simulation of a Spanish cohort of postmenopausal women and their possible osteoporotic fractures was done to assess the performance of two treatments for the prevention of vertebral and non-vertebral fractures in terms of cost-effectiveness. Simulation by means of a Markov model required that the disease evolution and the related events were simplified using a finite number of health states and the probabilities of moving from one state to another as the time go on. Markov models were adapted to reflect that the risk of suffering an event can change over time. This analytical model was applied to elucidate whether co-receptors testing is cost-effective to determine patient¿s suitability to benefit from the use of an antiretroviral treatment that includes maraviroc. All HIV strains require binding to CD4 plus at least one of the 2 co-receptors CCR5 or CXCR4 to enter human cells. Some HIV can use both co-receptors, and some individuals have a mixture of strains. Only patients with exclusively CCR5-tropic HIV are considered eligible to use the CCR5 antagonist maraviroc. A budget impact analyses to assess the economic effects of introducing eculizumab for treating the paroxysmal nocturnal hemoglobinuria was performed. Direct and indirect costs of this disease treatment were estimated and reported from the perspective of the health care system and from the societal perspective. Most of the published clinical studies are focused on measuring health in terms of efficacy and/or safety. But, sometimes the health and well-being quantification is not a direct measurement. Here, the calculation of the burden of disease for osteoporotic women who may suffer from fractures done at an individual level was presented in terms of disability adjusted life years (DALYs). Few studies of burden of diseases are available, and even less for Spanish population and performed using individual characteristics. The pharmacoeconomic studies can be useful in the health resources rationalization, and both budget impact analyses and new health measures are complementary tools. The work performed in this thesis constitutes a good example of methods application and adaptation to answer real clinical questions.
