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PubMed2004

Decision analysis and economic modelling: a primer.

In this primer, the reader is introduced to the concepts governing decision analysis and cost-effectiveness analysis. The construction of decision trees and Markov models is presented to provide the necessary background to critique research articles in published literature. Specific sub-topics related to cost-effectiveness analysis are discussed including quality adjustment and utilities (patient preferences for health states), discounting, and sensitivity analysis including Monte Carlo simulation. Evidence based methods to critique decision and cost-effectiveness analysis are provided, and limitations to these analytic methods are examined. In summary, the major functions of decision analysis and cost-effectiveness analysis are to provide: (1) a quantitative summary of existing data, and (2) hypothesis generation for further research.

Cost-Benefit Analysis↗
PubMed1970

Contingency counseling by school personnel: an economical model of intervention.

An Attendance Counselor contacted adults (mediators) who controlled reinforcers for six chronic nonattenders (targets); agreements (deals) were made between mediators and targets that reinforcers would be provided, contingent on school attendance. Absence of the Attendance Counselor from school for a two-week period constituted a reversal condition, after which the "deals" were reinstituted. Results showed a significant increase over baseline in school attendance during the time in which deals were in effect. A second study involved 20 chronic nonattenders for whom deals were arranged as in Study One (contingency counseling), and 15 nonattenders provided more traditional attendance counseling (contact counseling). Contingency Counselors achieved results with the 20 nonattenders similar to those achieved in Study One. An experienced Contact Counselor did not achieve improved school attendance among her group of 15 nonattenders.

Journal Article↗
PubMed2002

A health economic model to assess the long-term effects and cost-effectiveness of orlistat in obese type 2 diabetic patients.

OBJECTIVES: Obesity is a common condition in type 2 diabetic patients. Treating obesity may enhance hypoglycemic treatment and contribute to the reduction of long-term microvascular and macrovascular complications. Orlistat reduces cardiovascular risk factors in obese type 2 diabetic patients. The objectives of this study were to estimate the long-term clinical consequences of this weight loss and the resulting cost-effectiveness of treating obese type 2 diabetic patients with orlistat. RESEARCH DESIGN AND METHODS: A Markov model was developed to predict, over a 10-year period, the complication rates and mortality with and without a 2-year orlistat treatment, assuming a 5-year catch-up period after treatment. A stepwise approach was used to obtain the clinical data. First, the impact of weight loss with orlistat on HbA(1c), blood pressure, and cholesterol was assessed; then, the impact on mortality and micro- and macrovascular complications of decreasing these risk factors was applied. Four subgroups were studied based on the presence of risk factors. RESULTS: Cost-effectiveness varies between 3,462 Euro/life-year gained (LYG) for obese diabetic patients with hypertension and hypercholesterolemia and 19,986 Euro/LYG for obese diabetic patients without other risk factors. The latter result is not robust according to sensitivity analyses. CONCLUSIONS: Our results suggest that orlistat is cost-effective in the management of obese type 2 diabetic patients, especially in those with the presence of hypercholesterolemia and/or hypertension. Evidence on longer-term benefits of orlistat (>2 years) will be of importance for future decision-making.

Anti-Obesity Agents↗
PubMed2006

Surveillance of Barrett's oesophagus: exploring the uncertainty through systematic review, expert workshop and economic modelling.

OBJECTIVES: To assess what is known about the effectiveness, safety, affordability, cost-effectiveness and organisational impact of endoscopic surveillance in preventing morbidity and mortality from adenocarcinoma in patients with Barrett's oesophagus. In addition, to identify important areas of uncertainty in current knowledge for these programmes and to identify areas for further research. DATA SOURCES: Electronic databases up to March 2004. Experts in Barrett's oesophagus from the UK. REVIEW METHODS: A systematic review of the effectiveness of endoscopic surveillance of Barrett's oesophagus was carried out following methodological guidelines. Experts in Barrett's oesophagus from the UK were invited to contribute to a workshop held in London in May 2004 on surveillance of Barrett's oesophagus. Small group discussion, using a modified nominal group technique, identified key areas of uncertainty and ranked them for importance. A Markov model was developed to assess the cost-effectiveness of a surveillance programme for patients with Barrett's oesophagus compared with no surveillance and to quantify important areas of uncertainty. The model estimates incremental cost--utility and expected value of perfect information for an endoscopic surveillance programme compared with no surveillance. A cohort of 1000 55-year-old men with a diagnosis of Barrett's oesophagus was modelled for 20 years. The base case used costs in 2004 and took the perspective of the UK NHS. Estimates of expected value of information were included. RESULTS: No randomised controlled trials (RCTs) or well-designed non-randomised controlled studies were identified, although two comparative studies and numerous case series were found. Reaching clear conclusions from these studies was impossible owing to lack of RCT evidence. In addition, there was incomplete reporting of data particularly about cause of death, and changes in surveillance practice over time were mentioned but not explained in several studies. Three cost--utility analyses of surveillance of Barrett's oesophagus were identified, of which one was a further development of a previous study by the same group. Both sets of authors used Markov modelling and confined their analysis to 50- or 55-year-old white men with gastro-oesophageal reflux disease (GORD) symptoms. The models were run either for 30 years or to age 75 years. As these models are American, there are almost certainly differences in practice from the UK and possible underlying differences in the epidemiology and natural history of the disease. The costs of the procedures involved are also likely to be very different. The expert workshop identified the following key areas of uncertainty that needed to be addressed: the contribution of risk factors for the progression of Barrett's oesophagus to the development of high-grade dysplasia (HGD) and adenocarcinoma of the oesophagus; possible techniques for use in the general population to identify patients with high risk of adenocarcinoma; effectiveness of treatments for Barrett's oesophagus in altering cancer incidence; how best to identify those at risk in order to target treatment; whether surveillance programmes should take place at all; and whether there are clinical subgroups at higher risk of adenocarcinoma. Our Markov model suggests that the base case scenario of endoscopic surveillance of Barrett's oesophagus at 3-yearly intervals, with low-grade dysplasia surveyed yearly and HGD 3-monthly, does more harm than good when compared with no surveillance. Surveillance produces fewer quality-adjusted life-years (QALYs) for higher cost than no surveillance, therefore it is dominated by no surveillance. The cost per cancer identified approaches pound 45,000 in the surveillance arm and there is no apparent survival advantage owing to high recurrence rates and increased mortality due to more oesophagectomies in this arm. Non-surveillance continues to cost less and result in better quality of life whatever the surveillance intervals for Barrett's oesophagus and dysplastic states and whatever the costs (including none) attached to endoscopy and biopsy as the surveillance test. The probabilistic analyses assess the overall uncertainty in the model. According to this, it is very unlikely that surveillance will be cost-effective even at relatively high levels of willingness to pay. The simulation showed that, in the majority of model runs, non-surveillance continued to cost less and result in better quality of life than surveillance. At the population level (i.e. people with Barrett's oesophagus in England and Wales), a value of pound 6.5 million is placed on acquiring perfect information about surveillance for Barrett's oesophagus using expected value of perfect information (EVPI) analyses, if the surveillance is assumed to be relevant over 10 years. As with the one-way sensitivity analyses, the partial EVPI highlighted recurrence of adenocarcinoma of the oesophagus (ACO) after surgery and time taken for ACO to become symptomatic as particularly important parameters in the model. CONCLUSIONS: The systematic review concludes that there is insufficient evidence available to assess the clinical effectiveness of surveillance programmes of Barrett's oesophagus. There are numerous gaps in the evidence, of which the lack of RCT data is the major one. The expert workshop reflected these gaps in the range of topics raised as important in answering the question of the effectiveness of surveillance. Previous models of cost-effectiveness have most recently shown that surveillance programmes either do more harm than good compared with no surveillance or are unlikely to be cost-effective at usual levels of willingness to pay. Our cost--utility model has shown that, across a range of values for the various parameters that have been chosen to reflect uncertainty in the inputs, it is likely that surveillance programmes do more harm than good -- costing more and conferring lower quality of life than no surveillance. Probabilistic analysis shows that, in most cases, surveillance does more harm and costs more than no surveillance. It is unlikely, but still possible, that surveillance may prove to be cost-effective. The cost-effectiveness acceptability curve, however, shows that surveillance is unlikely to be cost-effective at either the 'usual' level of willingness to pay ( pound 20,000-30,000 per QALY) or at much higher levels. The expected value of perfect information at the population level is pound 6.5 million. Future research should target both the overall effectiveness of surveillance and the individual elements that contribute to a surveillance programme, particularly the performance of the test and the effectiveness of treatment for both Barrett's oesophagus and ACO. In addition, of particular importance is the clarification of the natural history of Barrett's oesophagus.

Adenocarcinoma↗
PubMedDate not supplied

[Ecologo-economical model of the region development based on the expert approach (example of Bieszczad montain region, Poland)].

A computer simulation has been developed for the dynamics of forest communities and abundance of wild animals in the Bieszczad mountain region (Carpathians, Southern Poland) at the background of changing quality of water resulting from the development of tourism and agriculture. The simulation operates on scaled variables in the 0-1 range. The functional relationships in the simulation were determined by the Delphi evaluation. The simulation was used to consider scenarios of various environmental influences of the region-climatic factors (warming and changed rainfall) as well as anthropogenic disturbances (development of tourism, agriculture, and commercial hunting). The simulation can be adapted for other regions.

Computer Simulation↗