Development and Validation of a Discrete Event Simulation Model to Evaluate the Cardiovascular Impact of Population Policies for Obesity.

INTRODUCTION: Our aim was to describe the development and validation of an obesity model representing the cardiovascular risks associated with different body mass index (BMI) categories, through simulation, designed to evaluate the epidemiological and economic impact of population policies for obesity. METHODS: A discrete event simulation model was built in R considering the risk of cardiovascular events (heart failure, stroke, coronary heart disease, and diabetes) associated with BMI categories in the Spanish population. The main parameters included in the model were estimated from Spanish hospital discharge records and the Spanish Health Survey and allowed both first-order and second-order (probabilistic sensitivity analysis) uncertainty to be programmed into the model. The simulation yielded the incidence and prevalence of cardiovascular events as validation outputs. To illustrate the capacity of the model, we estimated the reduction in cardiovascular events and cost-utility (incremental cost/incremental quality-adjusted life-years [QALYs]) of a hypothetical intervention that fully eliminated the cardiovascular risks associated with obesity and overweight. RESULTS: The Validation Status of Health-Economic decision models (AdViSHE) tool was applied. Internal validation plots showed adequate goodness of fit for the Spanish population. External validation was achieved by comparing the simulated and real incidence by age group for stroke, acute myocardial infarction, and heart failure. The intervention reduced the population hazard ratios of stroke, acute myocardial infarction, and heart failure to 0.81, 0.74, and 0.78, respectively, and added 0.74 QALYs to the whole population. CONCLUSIONS: This obesity simulation model evidenced good properties for estimating the long-term epidemiological and economic impact of policies to tackle obesity in Spain. The conceptual model could be implemented for other counties using country-specific input data.

[Cost-effectiveness methods of newborn screening assessment.] / Métodos para la evaluación económica de programas de cribado neonatal.

Newborn screening programs are a fundamental tool for secondary prevention or pre-symptomatic detection of certain conditions. The implementation of a newborn screening program requires an evaluation of effectiveness, safety, cost-effectiveness, feasibility and budget impact. Economic evaluation aims to contribute to the sustainability and solvency of health systems, especially when it comes to informing about financing health interventions with public funds. This funding must be justified on the basis of robust evidence of effectiveness, safety, cost-effectiveness, and acceptability. One of the most important limitations when evaluating the cost-effectiveness of a newborn screening program for hereditary disorders or congenital errors of metabolism is the scarcity of scientific evidence that limits the robustness of the economic analysis. Given the low availability of data, the use of expert opinion as a data source is unavoidable to complete the information. However, two main problems make it difficult to synthesize data obtained from various sources: biases and heterogeneity. Moreover, the measurement of quality-adjusted life years (QALYs) in pediatric populations poses serious methodological challenges. In Spain, although there is some heterogeneity in the supply of newborn screening programs between regions, guidelines are being established based on the best available scientific evidence to achieve the homogenization of newborn screening policies and programs at national level.

Los programas de cribado neonatal son una herramienta fundamental para la prevención secundaria o detección presintomática de determinadas afecciones. La implantación de un programa de cribado neonatal requiere necesariamente de una evaluación de su efectividad, seguridad, coste-efectividad, factibilidad e impacto presupuestario. La evaluación económica pretende contribuir a la sostenibilidad y solvencia de los sistemas sanitarios, especialmente a la hora de informar sobre la posible financiación, con fondos públicos, de intervenciones sanitarias como el cribado poblacional. Esta financiación debe justificarse en base a pruebas robustas de efectividad, seguridad, coste-efectividad y aceptabilidad. Una de las limitaciones más importantes a la hora de evaluar el coste-efectividad de un programa de cribado neonatal de trastornos hereditarios o de errores congénitos del metabolismo es la escasez de evidencia científica que limita la solidez y robustez del análisis de evaluación económica. Dada la baja disponibilidad de datos, el uso de la opinión de expertos como fuente de datos es inevitable para completar la información necesaria. Sin embargo, dos problemas principales dificultan la síntesis de datos obtenidos de varias fuentes: sesgos y heterogeneidad. Por otro lado, la medición de los años de vida ajustados por calidad (AVAC) en poblaciones pediátricas plantea serios desafíos metodológicos en un análisis de evaluación económica. En España, aunque existe cierta heterogeneidad en la oferta de programas de cribado neonatal entre CC.AA., se están estableciendo directrices basadas en la mejor evidencia científica disponible para conseguir la homogeneización de políticas y programas de cribado neonatal a nivel nacional.

On the Estimation of the Cost-Effectiveness Threshold: Why, What, How?

BACKGROUND: Many health care systems claim to incorporate the cost-effectiveness criterion in their investment decisions. Information on the system's willingness to pay per effectiveness unit, normally measured as quality-adjusted life-years (QALYs), however, is not available in most countries. This is partly because of the controversy that remains around the use of a cost-effectiveness threshold, about what the threshold ought to represent, and about the appropriate methodology to arrive at a threshold value. OBJECTIVES: The aim of this article was to identify and critically appraise the conceptual perspectives and methodologies used to date to estimate the cost-effectiveness threshold. METHODS: We provided an in-depth discussion of different conceptual views and undertook a systematic review of empirical analyses. Identified studies were categorized into the two main conceptual perspectives that argue that the threshold should reflect 1) the value that society places on a QALY and 2) the opportunity cost of investment to the system given budget constraints. RESULTS: These studies showed different underpinning assumptions, strengths, and limitations, which are highlighted and discussed. Furthermore, this review allowed us to compare the cost-effectiveness threshold estimates derived from different types of studies. We found that thresholds based on society's valuation of a QALY are generally larger than thresholds resulting from estimating the opportunity cost to the health care system. CONCLUSIONS: This implies that some interventions with positive social net benefits, as informed by individuals' preferences, might not be an appropriate use of resources under fixed budget constraints.

Projecting Burden of Dementia in Spain, 2010-2050: Impact of Modifying Risk Factors.

Risk and protective factors such as obesity, hypercholesterolemia, physical activity, and hypertension can play a role in the development of dementia. Our objective was to measure the effect of modification of risk and protective factors on the prevalence and economic burden of dementia in the aging Spanish population during 2010-2050. A discrete event simulation model including risk and protective factors according to CAIDE (Cardiovascular Risk Factors, Aging and Incidence of Dementia) Risk Score was built to represent the natural history of dementia. Prevalence of dementia was calculated from 2010 to 2050 according to different scenarios of risk factor prevalence to assess the annual social and health care costs of dementia. The model also supplied hazard ratios for dementia. Aging will increase between 49% and 16% each decade in the number of subjects with dementia. The number of working-age individuals per person with dementia will decrease to a quarter by 2050. An intervention leading to a 20% change in risk and protective factors would reduce dementia by 9% , prevent over 100,000 cases, and save nearly 4,900 million euros in 2050. Switching individuals from a group with a specific risk factor to one without it nearly halved the risk of the development of dementia. Dementia prevalence will grow unmanageable if effective prevention strategies are not developed. Interventions aiming to reduce modifiable risk factor prevalence represent valid and effective alternatives to reduce dementia burden. However, further research is needed to identify causal relationships between dementia and risk factors.

Cost-Effectiveness Analysis of a National Newborn Screening Program for Biotinidase Deficiency.

BACKGROUND AND OBJECTIVES: There are conflicting views as to whether testing for biotinidase deficiency (BD) ought to be incorporated into universal newborn screening (NBS) programs. The aim of this study was to evaluate the cost-effectiveness of adding BD to the panel of conditions currently screened under the national NBS program in Spain. METHODS: We used information from the regional NBS program for BD that has been in place in the Spanish region of Galicia since 1987. These data, along with other sources, were used to develop a cost-effectiveness decision model that compared lifetime costs and health outcomes of a national birth cohort of newborns with and without an early detection program. The analysis took the perspective of the Spanish National Health Service. Effectiveness was measured in terms of quality-adjusted life years (QALYs). We undertook extensive sensitivity analyses around the main model assumptions, including a probabilistic sensitivity analysis. RESULTS: In the base case analysis, NBS for BD led to higher QALYs and higher health care costs, with an estimated incremental cost per QALY gained of $24,677. Lower costs per QALY gained were found when conservative assumptions were relaxed, yielding cost savings in some scenarios. The probability that BD screening was cost-effective was estimated to be >70% in the base case at a standard threshold value. CONCLUSIONS: This study indicates that NBS for BD is likely to be a cost-effective use of resources.

Cost-effectiveness of the use of biomarkers in cerebrospinal fluid for Alzheimer's disease.

BACKGROUND: The use of cerebrospinal fluid (CSF) biomarkers could facilitate early detection of Alzheimer's disease (AD) in patients with mild cognitive impairment (MCI) and the differential diagnosis between AD and non-AD dementias. OBJECTIVE: To determine the cost-effectiveness of the use of amyloid-ß peptide (Aß42), total tau and phosphorylated tau proteins in CSF to diagnose AD in MCI and dementia patients. METHODS: An economic evaluation was performed by means of cost-effectiveness analysis comparing two AD diagnostic alternatives: the combined determination of Aß42 proteins, total tau and phosphorylated tau in CSF as biomarkers of AD, and the standard clinical diagnosis based on the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association (NINDS-ADRDA) criteria. A decision analytic model was developed to synthesize the identified evidence and to compare the costs and effectiveness associated with each diagnostic strategy. A probabilistic sensitivity analysis using 2nd order Monte Carlo simulations was performed. Subsequently, acceptability curves were calculated and ANCOVA models were applied to the results of the Monte Carlo simulations in order to identify the parameters that led greater variability in the model outcomes. RESULTS: The use of CSF biomarkers as an early diagnostic strategy of AD in MCI patients is a dominant alternative (less costly and more effective strategy than standard clinical diagnostic criteria). In dementia patients, although there is a higher uncertainty, biomarkers in CSF seem a more cost-effective alternative than standard clinical diagnostic criteria. CONCLUSIONS: Detecting AD in MCI patients by determining Aß42, total tau and phosphorylated tau proteins biomarkers in CSF is a cost-effective diagnostic alternative. No conclusive results were obtained on dementia patients.

Cost-utility analysis of gastric bypass for severely obese patients in Spain.

BACKGROUND: To assess the cost-utility of gastric bypass versus usual care for patients with severe obesity in Spain. METHODS: We have implemented a discrete-event simulation model with two branches: one branch involves gastric bypass, thereby reducing patients' BMI, and another branch where patients do not undergo surgery. The model analyzes the emergence of comorbidities (stroke, coronary obstructive disease, diabetes, and breast cancer) associated with obesity during a lifetime horizon. The selected measure of effectiveness is health-related quality of life. Both costs and effects are discounted at 3 %. A probabilistic sensitivity analysis is also performed using second-order Monte Carlo simulation; acceptability curves for different time horizons were also calculated. RESULTS: Patients with gastric bypass result in a lifetime increase of 5.63 quality-adjusted life years (QALYs) (18.18 vs. 12.55 QALYs). In addition, because of the reduced spending associated with the treatment of various obesity-related comorbidities, final savings stand at 13,994 . The total cost of the intervention branch is close to half the cost of the non-intervention branch (17,431 vs. 31,425 ). CONCLUSIONS: Gastric bypass is an intervention that dominates over the option of not intervening when a lifetime horizon is considered.