Trine Kjær

Disentangling WTP per QALY data: different analytical approaches, different answers

A large random sample of the Danish general population was asked to value health improvements by way of both the time trade-off elicitation technique and willingness-to-pay (WTP) using contingent valuation methods. The data demonstrate a high degree of heterogeneity across respondents in their relative valuations on the two scales. This has implications for data analysis. We show that the estimates of WTP per QALY are highly sensitive to the analytical strategy. For both open-ended and dichotomous choice data we demonstrate that choice of aggregated approach (ratios of means) or disaggregated approach (means of ratios) affects estimates markedly as does the interpretation of the constant term (which allows for disproportionality across the two scales) in the regression analyses. We propose that future research should focus on why some respondents are unwilling to trade on the time trade-off scale, on how to interpret the constant value in the regression analyses, and on how best to capture the heterogeneity in preference structures when applying mixed multinomial logit.

The Patient Perspective of Diabetes Care: A Systematic Review of Stated Preference Research

BackgroundThe importance of understanding the perspective of patients towards their own care is increasingly recognized, both in clinical practice and in pharmaceutical drug development. Stated preference methods to assess the preference of patients towards different aspects of diabetes treatment have now been applied for over a decade.ObjectiveOur goal was to examine how stated preference methods are applied in diabetes care, and to evaluate the value of this information in developing the patient perspective in clinical and policy decisions.MethodsA systematic review was conducted in accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement. The information sources were MEDLINE, EMBASE, Biosis, Current Contents, Web of Science, CINAHL, PsycINFO, and EconLit.ResultsThree contingent valuation studies and 11 discrete choice experiments were retrieved. The majority of studies were conducted from 2009 onwards, but some date back to 1998. The reasons provided for applying the stated preference methods were to help differentiate between products, or to enable inclusion of the patient’s perspective in treatment decisions. The main aspects of treatment examined were related to glucose control, adverse events, and drug administration. The majority of patients preferred glucose control over avoiding minor hypoglycemic events. Patient willingness to pay was above

The influence of information and private versus public provision on preferences for screening for prostate cancer: A willingness-to-pay study

US100/month for glucose control, avoiding immediate health hazards such as nausea, and oral or inhaled drug administration. Preference towards drug administration was highly associated with previous experience with injectable diabetes medicine.ConclusionsThe ability of a drug to lower glucose levels plays a decisive role in the choice between alternative treatments. Future research should strive to develop questionnaire designs relevant for the decision context of the study. That is, if the aim is to foster shared decision making, in clinical practice or drug development, this should guide the study design. Furthermore, concise reporting of all study dimensions—from the qualitative prework to the analysis stage—is warranted.

FRAMING THE WILLINGNESS-TO-PAY QUESTION: IMPACT ON RESPONSE PATTERNS AND MEAN WILLINGNESS TO PAY

This study investigates the influence of information and public versus private provision on preferences for introducing screening (i.e. PSA-test) for prostate cancer in Denmark. The aim is to disclose if preferences (measured as willingness-to-pay) are influenced by whether the service is provided by the private or public health care sector, and the extent to which negative information on the PSA-test influences the perceptions of the screening programme. It is also investigated whether the impact of information differs dependent on public-private provision. A random sample of the Danish male population (all between 50 and 70 years of age) were invited to fill out a web-based questionnaire. It was found that two thirds of the respondents were willing to participate and willing to pay for a public intervention programme, when provided with all relevant information. In contrast, only approximately one third were so inclined if a prostate cancer screening service was offered by private clinics. Results suggest that public provision framing increases the perceived value of the screening programme, and that the provision of full information regarding the negative characteristics of the programme decreases programme valuation.

Scope insensitivity in contingent valuation studies of health care services: should we ask twice?

In this study, respondents were randomly allocated to three variants of the payment card format and an open-ended format in order to test for convergent validity. The aim was to test whether preferences (as measured by willingness to pay additional tax) would be affected by framing the willingness-to-pay question differently. Results demonstrated that valuations were highly sensitive to whether respondents were asked to express their maximum willingness to pay per month or per year. Another important finding is that the introduction of a binary response filter prior to the payment card follow-up tends to eliminate the positive aspects of introducing a payment card and produces response patterns that are much in line with those of the open-ended contingent valuation format. However, although a filter will impact on the distribution of willingness-to-pay bids and on the rate of zero and protest bids, the overall impact on the welfare estimate is minor. The outcomes of this study indicate that valuations in the stated preference literature may be, at least in part, a function of the instrument designed to obtain the valuations.

Does question order influence sensitivity to scope? Empirical findings from a web-based contingent valuation study

The main purpose of the present study was to test for outcome scope insensitivity. Respondents were initially asked to value one of two severe health states by way of a time-trade-off (TTO) exercise. Subsequent to the TTO exercise all respondents were asked to value an intervention, which offered a reduction in risk of falling into the health state they had evaluated. All respondents were subsequent to this initial CV exercise asked to value the same risk reduction, but in this case the outcome was death. Although our study passes the internal scope test, there is not a high degree of sensitivity to outcome. As many as 68% of respondents stated an identical maximum WTP in first and second CV valuation exercise implying that they value the interventions equally despite the fact that the health state presented in the initial CV question was deemed far better than death according to the TTO responses given by the same respondents. In contrast, the external scope test (comparison of response to initial CV across study arms) fared much better.

Associations between patients’ risk attitude and their adherence to statin treatment – a population based questionnaire and register study

This paper examines the relationship between question order and sensitivity to scope in a large-scale web-based stated preference survey using an Internet panel. Results are presented from a contingent valuation survey in which each individual was asked to value two independent gains in life expectancy. Using split-sample data for question order we are able to study sensitivity to scope by carrying out an internal as well as an external scope test, and to examine whether question order influences sensitivity to scope. Finally, we address whether our results raise some specific concerns regarding the use of web-based surveys. Overall we find that choice of elicitation approach – in this case bottom-up versus top-down – influences the stated willingness-to-pay values leading to order effects and differences in scope sensitivity. Our findings demonstrate that elicitation approach affects the decision-making strategy, suggesting that preferences at least to some extent are reference dependent and constructed during the elicitation task. In addition, our findings indicate some relation between scope insensitivity, time spent on filling out the questionnaire and experience as an Internet panel member.

Soccer Attendees’ Preferences for Facilities at the Fionia Park Stadium: An Application of the Discrete Choice Experiment

BackgroundPoor adherence to medical treatment may have considerable consequences for the patients’ health and for healthcare costs to society. The need to understand the determinants for poor adherence has motivated several studies on socio-demographics and comorbidity. Few studies focus on the association between risk attitude and adherence. The aim of the present study was to estimate associations between patients’ adherence to statin treatment and different dimensions of risk attitude, and to identify subgroups of patients with poor adherence.MethodsPopulation-based questionnaire and register-based study on a sample of 6393 persons of the general. Danish population aged 20–79. Data on risk attitude were based on 4 items uncovering health-related as well as financial dimensions of risk attitude. They were collected through a web-based questionnaire and combined with register data on redeemed statin prescriptions, sociodemographics and comorbidity. Adherence was estimated by proportion of days covered using a cut-off point at 80 %.ResultsFor the dimension of health-related risk attitude, “Preference for GP visit when having symptoms”, risk-neutral and risk-seeking patients had poorer adherence than the risk-averse patients, OR 0.80 (95 %-CI 0.68–0.95) and OR 0.83 (95 %-CI 0.71–0.98), respectively. No significant association was found between adherence and financial risk attitude. Further, patients in the youngest age group and patients with no CVD were less adherent to statin treatment.ConclusionWe find some indication that risk attitude is associated with adherence to statin treatment, and that risk-neutral and risk-seeking patients may have poorer adherence than risk-averse patients. This is important for clinicians to consider when discussing optimal treatment decisions with their patients. The identified subgroups with the poorest adherence may deserve special attention from their GP regarding statin treatment.

From representing views to representativeness of views: Illustrating a new (Q2S) approach in the context of health care priority setting in nine European countries

The discrete choice experiment (DCE) is introduced in sports economics by empirically investigating soccer attendees’ preferences for facilities at a soccer stadium in Denmark. The appropriateness of the strategy of differentiating prices based on quality of opponents (A vs. B matches) is investigated. The results indicate that respondents are capable of understanding the exercise. The DCE is a useful and valid tool in assessing the strength of preferences for stadium facilities. The study found positive preferences for the investigated facilities, except for the use of cheerleaders where the authors observed some heterogeneity.

Public preferences for establishing nephrology facilities in Greenland: estimating willingness-to-pay using a discrete choice experiment

Governments across Europe are required to make decisions about how best to allocate scarce health care resources. There are legitimate arguments for eliciting societal vales in relation to health care resource allocation given the roles of the general public as payers and potential patients. However, relatively little is known about the views of the general public on general principles which could guide these decisions. In this paper we present five societal viewpoints on principles for health care resources allocation and develop a new approach, Q2S, designed to investigate the extent to which these views are held across a range of European countries. An online survey was developed, based on a previously completed study Q methodology, and delivered between November 2009 and February 2010 across nine countries to 33,515 respondents. The largest proportion of our respondents (44%), were found to most associate themselves with an egalitarian perspective. Differences in views were more strongly associated with countries than with socio-demographic characteristics. These results provide information which could be useful for decision makers in understanding the pluralistic context in which they are making health care resource allocation decisions and how different groups in society may respond to such decisions.