Persona: Pérez Martín, Jorge
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Pérez Martín
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Publicación OpenMarkov, an Open-Source Tool for Probabilistic Graphical Models(International Joint Conference on Artificial Intelligence, 2019) Arias Calleja, Manuel; Pérez Martín, Jorge; Luque Gallego, Manuel; Díez Vegas, Francisco JavierOpenMarkov is a Java open-source tool for creating and evaluating probabilistic graphical models, including Bayesian networks, influence diagrams, and some Markov models. With more than 100,000 lines of code, it offers some features for interactive learning, explanation of reasoning, and cost-effectiveness analysis, which are not available in any other tool. OpenMarkov has been used at universities, research centers, and large companies in more than 30 countries on four continents. Several models, some of them for real-world medical applications, built with OpenMarkov, are publicly available on Internet.Publicación Análisis de coste-efectividad en OpenMarkov. Aplicación al implante coclear bilateral pediátrico en España(Universidad Nacional de Educación a Distancia (España). Escuela Técnica Superior de Ingeniería Informática. Departamento de Inteligencia Artificial., 2015-10-05) Pérez Martín, JorgeEl uso de implantes cocleares es, a día de hoy la terapia más efectiva para el tratamiento de la sordera severa y profunda. Diferentes estudios han demostrado que el implante coclear unilateral es coste-efectivo en niños y en adultos. Investigaciones recientes indican que el implante coclear bilateral (un implante en cada oído) es coste-efectivo en niños, pero el grado de incertidumbre sigue siendo elevado. El objetivo de este estudio consiste en determinar con la mayor precisión posible si el implante coclear bilateral pediátrico es coste-efectivo. Con este fin se ha construido un modelo gráfico probabilista que representa los sucesos que pueden producirse a lo largo de la vida del usuario, su impacto en la calidad de vida y los costes asociados, distinguiendo los costes que cubre el sistema nacional de sanidad de los que en España asumen los usuarios y sus familias. La construcción y la evaluación del modelo se han realizado con la herramienta de software libre OpenMarkov, desarrollada en Centro de Investigación sobre Sistemas Inteligentes de Ayuda a la Decisión (CISIAD) de la UNED, para lo cual se han añadido nuevas funcionalidades y se han extendido algunas de las ya existentes. Varios estudios han estimado que la disposición a pagar (también conocida como “umbral de coste-efectividad”) implícitamente utilizada por el sistema de sanidad español si sitúa entre entre 30.000 y 35.000 € por año de vida ajustado en calidad (AVAC). Según los resultados de nuestro modelo, la razón de coste-efectividad incremental (RCEI) del implante simultáneo frente al unilateral para niños de un año de edad es de 12.133 €/AVAC, lo cual implica que conviene poner dos implantes todos los que los necesitan. El análisis de sensibilidad confirma esta conclusión, pues para un umbral de 30.000 €/AVAC la probabilidad de que esta intervención sea coste-efectivo alcanza el 98 %. Incluso en el caso de que el sistema nacional de salud asumiera los costes que en nuestro país cubren actualmente las familias,la intervención seguiría siendo coste-efectiva, con una RCEI de 17.263 €/AVAC y una probabilidad del 94 %. La implantación debe hacerse de forma simultánea, es decir, en una sola operación quirúrgica, porque la implantación secuencial tiene la misma efectividad pero mayor coste para el sistema sanitario y para la familia. Nuestro modelo no es capaz de estimar la RCEI para niños mayores de un año porque la efectividad depende de muchos factores, principalmente de la edad actual, cuándo apareció la sordera, cuándo fue diagnosticada y, en su caso, cuándo se realizó el primer implante. Este modelo estará disponible públicamente para que otros investigadores puedan reproducir los resultados y adaptarlo a otros contextos. En particular, sería interesante analizar la RCEI en adultos y en otros países.Publicación Evaluation of Markov models with discontinuities(Society for Medical Decision Making, 2019-02-07) Bermejo, Iñigo; Pérez Martín, Jorge; Díez Vegas, Francisco JavierBackground. Several methods, such as the half-cycle correction and the life-table method, were developed to attenuate the error introduced in Markov models by the discretization of time. Elbasha and Chhatwal have proposed alternative “corrections” based on numerical integration techniques. They present an example whose results suggest that the trapezoidal rule, which is equivalent to the half-cycle correction, is not as accurate as Simpson’s 1/3 and 3/8 rules. However, they did not take into consideration the impact of discontinuities. Objective. To propose a method for evaluating Markov models with discontinuities. Design. Applying the trapezoidal rule, we derive a method that consists of adjusting the model by setting the cost at each point of discontinuity to the mean of the left and right limits of the cost function. We then take from the literature a model with a cycle length of 1 year and a discontinuity on the cost function and compare our method with other “corrections” using as the gold standard an equivalent model with a cycle length of 1 day. Results. As expected, for this model, the life-table method is more accurate than assuming that transitions occur at the beginning or the end of cycles. The application of numerical integration techniques without taking into account the discontinuity causes large errors. The model with averaged cost values yields very small errors, especially for the trapezoidal and the 1/3 Simpson rules. Conclusion. In the case of discontinuities, we recommend applying the trapezoidal rule on an averaged model because this method has a mathematical justification, and in our empirical evaluation, it was more accurate than the sophisticated 3/8 Simpson rule.Publicación Markov influence diagrams: a graphical tool for cost-effectiveness analysis(Society for Medical Decision Making, 2017-01-11) Yebra, Mar; Bermejo, Iñigo; Palacios Alonso, Miguel Ángel; Arias Calleja, Manuel; Luque Gallego, Manuel; Pérez Martín, Jorge; Díez Vegas, Francisco JavierMarkov influence diagrams (MIDs) are a new type of probabilistic graphical models that extend influence diagrams in the same way as Markov decision trees extend decision trees. They have been designed to build state-transition models, mainly in medicine, and perform cost-effectiveness analysis. Using a causal graph that may contain several variables per cycle, MIDs can model various features of the patient without multiplying the number of states; in particular, they can represent the history of the patient without using tunnel states. OpenMarkov, an open-source tool, allows the decision analyst to build and evaluate MIDs—including cost-effectiveness analysis and several types of deterministic and probabilistic sensitivity analysis—with a graphical user interface, without writing any code. This way, MIDs can be used to easily build and evaluate complex models whose implementation as spreadsheets or decision trees would be cumbersome or unfeasible in practice. Furthermore, many problems that previously required discrete event simulation can be solved with MIDs, i.e., within the paradigm of state-transition models, in which many health economists feel more comfortable.Publicación Cost-effectiveness of Pediatric Bilateral Cochlear Implantation in Spain(Wiley Online Library, 2017) Artaso, Miguel A.; Díez, Francisco Javier; Pérez Martín, JorgeObjective: To determine the incremental cost-effectiveness of bilateral versus unilateral cochlear implantation for one-year-old children suffering from bilateral sensorineural severe to profound hearing loss from the perspective of the Spanish public health system. Study Design: Cost-utility analysis. Methods: We conducted a general-population survey to estimate the quality of life increase contributed by the second implant. We built a Markov influence diagram and evaluated it for a life-long time horizon with a 3% discount rate in the base case. Results: The incremental cost-effectiveness ratio (ICER) of simultaneous bilateral implantation with respect to unilateral implantation for one-year-old children with severe to profound deafness is €10,323 per quality-adjusted life year (QALY). For sequential bilateral implantation, it rises to €11,733/QALY. Both options are cost-effective for the Spanish health system, whose willingness to pay is estimated at around €30,000/QALY. The probabilistic sensitivity analysis shows that the probability of bilateral implantation being cost-effective reaches 100% for that cost-effectiveness threshold. Conclusions: Bilateral implantation is clearly cost-effective for the population considered. If possible, it should be done simultaneously, i.e., in one surgical operation, because it is as safe and effective as sequential implantation, and saves costs for the system and for users and their families. Sequential implantation is also cost-effective for children who have received the first implant recently, but it is difficult to determine when it ceases to be so because of the lack of detailed data. These results are specific for Spain but the model can easily be adapted to other countries. Level of Evidence: 2C