Modelos matemáticos para la evaluación económica: los modelos dinámicos basados en ecuaciones diferenciales Mathematical models for economic evaluation: dynamic models based on differential equations

La utilización conjunta de árboles de decisión y modelos epidemiológicos basados en ecuaciones diferenciales es un método apropiado para la evaluación económica de medidas profilácticas ante enfermedades infecciosas. Estos modelos permiten combinar el comportamiento dinámico de la enfermedad con el consumo de recursos sanitarios. Para ilustrar este tipo de modelos se ajusta un sistema dinámico de ecuaciones diferenciales al comportamiento epidémico de la gripe en España, con el fin de proyectar el impacto epidemiológico de la vacunación antigripal. Los resultados del modelo dinámico se implementan en un diagrama con estructura de árbol para medir el consumo de recursos sanitarios y su repercusión en términos monetarios.The joint utilization of both decision trees and epidemiological models based on differential equations is an appropriate method for the economic evaluation of preventative interventions applied to infectious diseases. These models can combine the dynamic pattern of the disease together with health resource consumption. To illustrate this type of model, we adjusted a dynamic system of differential equations to the epidemic behavior of influenza in Spain, with a view to projecting the epidemiologic impact of influenza vaccination. The results of the epidemic model are implemented in a diagram with the structure of a decision tree so that health resource consumption and the economic implications can be calculated

Utilización del cuestionario European Quality of Life-5 Dimensions (EQ-5D) para valorar la variación de la calidad de vida relacionada con la salud debida a la gripe

Objective: To describe self-perceived health status and health-related quality of life (HRQoL) in healthy individuals of working age, to measure changes due to influenza infection, and to evaluate the effect of influenza infection on HRQoL in monetary terms. Method: We performed a descriptive observational study through questionnaires administered to 50 patients of working age infected with the influenza virus during the epidemiologic year 2004-2005 and living in private homes of the city of Logroño (Spain). The patients completed the questionnaires twice: with and without influenza. The dimensions and HRQoL indicators of the European Quality of Life-5 Dimensions (EQ-5D) questionnaire were evaluated. HRQoL utility indices were used to calculate lost quality-adjusted life years (QALYs). Results: On average, the reduction in the HRQoL utility index caused by influenza infection was between 0.37 and 0.65, on a scale from 0 (death) to 1 (perfect health). An influenza epidemic in 100,000 individuals could imply a loss of 137 QALYs, which in monetary terms could represent 2,722,609. Conclusions: The EQ-5D dimension most negatively affected by influenza was «daily activities» while the least affected dimension was «anxiety/depression». Influenza causes substantial losses in HRQoL among the population of working age. The results of the sensitivity analysis of the monetary effects of influenza infection yielded intervals showing a range of more than 5 times the mean value. © 2007 SESPAS

Las bebidas alcohólicas en España: Salud y economía

Desde diversos foros de la salud pública se insiste en las consecuencias negativas para la salud derivadas del consumo de alcohol, así como en otras consecuencias sociales también del mismo signo; sin embargo, en los medios de comunicación observamos cómo se potencia su consumo y cómo una buena parte de la industria y del sector turístico pivota sobre la oferta de estos bienes. Desconocemos si, como en muchas ocasiones, en el término medio está la virtud; lo que desde luego está claro, por los resultados presentados más adelante, es que la virtud no reside en el término en que se sitúa el actual consumo. Seguidamente se describirán la estructura del sector productivo del alcohol, algunas pautas de su consumo y las consecuencias que acarrea, para luego pasar a citar las políticas públicas, haciendo especial hincapié en las de carácter fiscal, y a efectuar una evaluación en cuanto a su capacidad para reducir el consumo. Finalmente, se presentan algunas conclusiones y vías de avance orientadas a fomentar la investigación para conocer mejor los aspectos económicos y de salud pública relacionados con el alcohol, y así diseñar políticas de salud pública más eficace

Dynamic Modelling of Infectious Diseases: An Application to the Economic Evaluation of Influenza Vaccination

Objective: To evaluate the economic efficiency of influenza vaccination using both dynamic and static modelling approaches. Setting: The Spanish National Health System. Design and methods: We modelled the progress of an influenza epidemic in Spain according to the epidemiological pattern of susceptible->infective->resistant, employing a non-linear system of ordinary differential equations that enables the measurement of epidemiological effects of an anti-influenza vaccination. We used a decision tree to represent the repercussion on healthcare resources use and on financial resources. The same analyses were conducted using a static approach, and the results were compared. Healthcare costs were valued in _, year 2005 values. Results: For the base case, the impact of the healthcare intervention (vaccination) was not efficient from the perspective of the healthcare payer when using a static approach (return rate 0.28 per _ invested in vaccination). Nevertheless, it was efficient when employing a dynamic approach (return rate 1.22 per _). Furthermore, a considerable freeing of healthcare resources would have been produced over the entire influenza season. Conclusions: The indirect effect of vaccination on the non-vaccinated individuals (the `herd immunity effect') can be greater than the direct effect on individuals vaccinated. This implies that the herd immunity effect needs to be taken into consideration in the economic evaluations of prophylactic measures employed against infectious diseases.Cost-analysis, Influenza-virus-infections, Influenza-virus-vaccine, Modelling