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Objective. The authors performed a methodological comparison of the usual standard gamble with methods that could also be used in mailed questionnaires.Methods.Ninety-two diabetic patients valued diabetes-related health states twice. In face-to-face interviews, the authors used an iterative standard gamble (ISG) in which the probabilities were varied in a ping-pong manner and a self-completion method (SC) with top-down titration as search procedure (SC-TD) in 2 independent subsamples of 46 patients. Three months later, all patients received a mailed questionnaire in which the authors used the self-completion method with bottom-up (SCBU) and SC-TD as search procedures.Results.ISG and SCTD showed feasibility and consistency in the interviews. The ISG resulted in significantly higher utilities than the SC-TD. Two thirds of the mailed questionnaires provided useful results indicating some problems of feasibility. Utilities measured by SC-BU and SC-TD did not differ significantly showing procedural invariance. Further, patients indicated ambivalence when given the choice not to definitely state their preferences.Conclusions.The results show that different strategies to collect standard gamble utilities can yield different results. Compared with the usually applied ISG, the SC method is feasible in interviews and provides a consistent alternative that is less costly when used in mailed questionnaires, although its practicability has to be improved in this later setting.
Chickenpox infections are generally mild but due to their very high incidence among healthy children they give rise to considerable morbidity and occasional mortality. With the development of a varicella vaccine in the early 1970s and its progressive licensing in many countries, interest in the efficiency of varicella immunisation programmes grew. The objective of this review was to discuss the methodological aspects and results of published economic evaluations of varicella vaccination. From this, we attempted to make recommendations.
A computerised search was carried out; 17 full economic evaluations of varicella vaccination were retrieved. The review identified the methodological divergences and similarities between the articles in four areas: study design, epidemiological data, economic data and model characteristics. We assessed to what extent the applied methods conform to general guidelines for the economic evaluation of healthcare interventions and compared the studies’ results.
The desirability of a universal vaccination programme depends on whose perspective is taken. Despite variability in data and model assumptions, the studies suggest that universal vaccination of infants is attractive to society because large savings occur from averted unproductive days for parents. For the healthcare payer, universal vaccination of infants does not generate savings. Vaccination of susceptible adolescents has been proposed by some authors as a viable alternative; the attractiveness of this is highly dependent on the negative predictive value of anamnestic screening. Targeted vaccination of healthcare workers and immunocompromised individuals appears relatively cost effective. Findings for other target groups are either contradictory or provide insufficient evidence for any unequivocal recommendations to be made. High sensitivity to vaccine price was reported in most studies.
This review highlights that some aspects of these studies need to be further improved before final recommendations can be made. First, more transparency, completeness and compliance to general methodological guidelines are required. Second, because of the increasing severity of varicella with age, it is preferable and in some cases essential to use dynamic models for the assessment of universal vaccination strategies. Third, most studies focused on the strategy of vaccinating children only while their results depended heavily on disputable assumptions (regarding vaccine effectiveness and impact on herpes zoster). Since violation of these assumptions could have important adverse public health effects, we suggest pre-adolescent vaccination as a more secure alternative. This option deserves more attention in future analyses.
For cost–benefit analysis, health technologies with multiple effects should be valued in a single scenario by a holistic willingness‐to‐pay (WTP) measure. Recent studies instead used decomposed scenarios in which respondents report their WTP for each individual effect. Evidence can be found that the sum of such decomposed WTPs overestimates the holistic WTP, i.e. the holistic WTP is sub‐additive. This sum of decomposed WTPs can lead to wrong conclusions on the efficiency of health technologies. This is also relevant in decision making about new technologies that are valued separately in different surveys. To date, no utility‐theoretical and empirically validated aggregation function for decomposed WTPs exists. Within an expected utility model, this paper identifies as a reason for sub‐additivity – beside risk aversion with respect to wealth – a negative influence of better health on the marginal utility of wealth, i.e. marginal utility of wealth is smaller in better health states. Assuming mutual utility independence of health and wealth, a theoretically founded aggregation function covering these two impacts is derived. In a contingent valuation study, 92 patients with diabetes were asked to state their WTP for reductions of the risk of several diabetic complications in decomposed as well as in holistic scenarios. The patients had preferences with a significant negative influence of health on the marginal utility of wealth. Sub‐additivity occurred and theoretically founded aggregation could considerably lower the degree of overestimation. These results suggest that the theoretically founded aggregation function might reduce problems of sub‐additivity that can be economically relevant. Further empirical testing of the approach is indicated.
Creating long-lived software systems requires a technol ogy to build systems with good maintainability. One of the core ideas of the Model Driven Architecture (MDA) is to ease the change of the run-time platform by raising the level of abstraction in which just the business aspects are modelled, and by separating business aspects from techni cal issues and implementation details. This article anal yses the MDA approach with respect to maintainability. We argue that MDA systems will become even harder to maintain because the maintainability depends on the sys tem's (development) environment. MDA, UML and other base technologies are still under development, therefore the tools will change considerably. While the MDA possibly eases the change of the run-time platform, we show that it is quite difficult to exchange a link in the development tool chain. Our argumentation is based on the general proper ties of software evolution and the dependency chains in the development and run-time environments. It is backed by experiences with MDA development as well as by analo gies to general maintenance experiences.
Java Server Faces
(2004)
The strong technical orientation of the previous multimedia evolution shows a lack of theoretical foundation. Both during the evolution and application of multimedia technology, well-founded theoretical concepts are missing. The intention of this paper is to show categories of different information representations and interaction types and their strengths in representing contents. A classification of multimedia information and interaction types is given also as an
overview of the problem fields of multimedia, especially in the field of learning theory. This classification is used to give some guidelines for using and combining multimedia contents in multimedia systems.
Process Modelling with ARIS®
(2004)