Convergent validity between a discrete choice experiment and a direct, open-ended method: comparison of preferred attribute levels and willingness to pay estimates

The Discrete Choice Experiment (DCE) has become increasingly popular as a method for eliciting patient or population preferences. If DCE estimates are to inform health policy, it is crucial that the answers they provide are valid. Convergent validity is tested in this paper by comparing the results of a DCE exercise with the answers obtained from direct, open-ended questions. The two methods are compared in terms of preferred attribute levels and willingness to pay (WTP) values. Face-to-face interviews were held with 292 women in Calgary, Canada. Similar values were found between the two methods with respect to preferred levels for two out of three of the attributes examined. The DCE predicted less well for levels outside the range than for levels inside the range reaffirming the importance of extensive piloting to ensure appropriate level range in DCEs. The mean WTP derived from the open-ended question was substantially lower than the mean derived from the DCE. However, the two sets of willingness to pay estimates were consistent with each other in that individuals who were willing to pay more in the open-ended question were also willing to pay more in the DCE. The difference in mean WTP values between the two approaches (direct versus DCE) demonstrates the importance of continuing research into the different biases present across elicitation methods.     

The effects of convenience and quality on the demand for vaccination: Results from a discrete choice experiment

BackgroundVaccination is an effective way to prevent infectious diseases. Most studies analysed people's vaccine decisions, but few studies have analysed the effects of convenience such as immunisation schedule and distance and the quality of vaccination service on vaccination uptake.ObjectiveThe aim of this paper was to investigate adults’ preferences for convenience and quality of vaccination service, calculate the private economic benefit from convenience (vaccination schedule and distance) and quality, and predict the uptake rate for different vaccine scenarios.MethodsIn our study, we interviewed 266 adults in 2 counties of Shandong province in China. The discrete choice experiment (DCE) was employed to analyse the preference for hepatitis B virus (HBV) vaccination, and a mixed logit model was used to estimate respondent preferences for vaccination attributes included in the DCE.ResultsThe protection rate against hepatitis B (HB), duration of protection, risk of side effects, vaccination cost, schedule, and vaccination sites were proved to influence adults’ preferences for HBV vaccination. The estimated willingness to pay (WTP) for 1 dose schedule instead of 3 doses and for a third-level vaccination site instead of a first-level site was almost equal (19 RMB). However, if the protection duration of the vaccination programme changed from 5 years to 20 years, the adults were willing to pay 35.05 RMB, and WTP for a 99% protection rate instead of a 79% rate was 67.71 RMB. The predicted uptake rate is almost 43% for the base case of HBV vaccination.ConclusionsAdults made trade-offs between vaccination schedules, vaccination sites, and other characteristics of HBV vaccine. The impact of attributes of the vaccine itself, especially protection rate against HB, duration of protection, and risk of side-effects, is more dramatic than convenience and quality of vaccination service.     

Estimating the value of social care

Increasingly, health economists are required to work across sectors when evaluating options for improving health, health care and well-being. Social care is a key sector which is both influenced by and influences the use and outcomes of health services. This paper reports on a developing approach to measuring social care outcome, designed to reflect outcomes across client groups. In this process it is important that we reflect the relative importance or value of these domains of outcome. This paper reports on a pilot study that investigated the feasibility of using discrete choice experiments to identify a financial “willingness to accept” valuation of a large number of domains and investigated factors associated with variations in respondents’ preferences. We conclude that, while the domains themselves need further work, the approach provides a helpful starting point in the difficult issue of reflecting population preferences for a large number of social care outcome domains.     

Decisions about Pap tests: What influences women and providers?

Despite the success internationally of cervical screening programs debate continues about optimal program design. This includes increasing participation rates among under-screened women, reducing unnecessary early re-screening, improving accuracy of and confidence in screening tests, and determining the cost-effectiveness of program parameters, such as type of screening test, screening interval and target group. For all these issues, information about consumer and provider preferences and insight into the potential impact of any change to program design on consumer and provider behaviour are essential inputs into evidence-based health policy decision making. This paper reports the results of discrete choice experiments to investigate women's choices and providers' recommendations in relation to cervical screening in Australia. Separate experiments were conducted with women and general practitioners, with attributes selected to allow for investigation of how women and general practitioners differ in their preferences for attributes of screening programs. Our results indicate a considerable commonality in preferences but the alignment was not complete. Women put relatively more weight on cost, chance of a false positive and if the recommended screening interval were changed to one year.     

Mothers' preferences and willingness to pay for HPV vaccines in Vinh Long Province, Vietnam

About 530,000 women develop cervical cancer worldwide and 275,000 die from the disease each year. Eighty percent of these deaths occur in developing countries. In Vietnam, cervical cancer has recently emerged as the most common type of cancer in women, and there are no national screening programs for cervical cancer. Since 2009, two different human papillomavirus (HPV) vaccines have been licensed for use in Vietnam, but access to these vaccines is generally limited to people who live in urban areas. Studies have shown that HPV vaccination may be cost-effective in cervical cancer prevention in Vietnam, depending on vaccination costs. Given that current HPV vaccines are expensive and public health funding for supporting a rapid introduction of the vaccine is limited, expanding and sustaining access to the HPV vaccine may require alternative financing mechanisms, such as fees-based immunization services. A conjoint analysis study was conducted with mothers of girls 9-17 years of age in Vinh Long Province in Vietnam to estimate the mothers' demand for HPV vaccines for their daughters and to measure the tradeoffs between vaccine fees and vaccine uptake. The results suggest that the demand for HPV vaccines was high, increased with vaccine effectiveness and duration of effectiveness, and decreased with vaccine cost. Vaccine effectiveness was the most important vaccine attribute to these mothers, followed by duration of effectiveness. The predicted probability of respondents buying an HPV vaccine that was 70% effective for 10 years varied by the price, ranging from 30% when the vaccine price was $353 per course, to 68% when the vaccine cost $6 per course. As expected, demand and predicted purchase probability were higher among groups with higher socioeconomic status.     

Determinants of willingness to pay for self-paid vaccines in China

Background

While vaccines not covered by China's Expanded Program on Immunization can be received voluntarily with out-of-pocket payment, the uptake of self-paid vaccines in China is low.

Objective

To investigate willingness to pay (WTP) for self-paid vaccines and its determinants in China.

Methods

We interviewed 2160 randomly selected households with children 0–3 years old, in 108 communities from three provinces in 2013. A bidding game method was used to elicit WTP for two self-paid vaccines: 7-valent pneumococcal conjugate vaccine and influenza vaccine. We conducted multivariate linear regressions to determine factors affecting the WTP.

Results

Median WTP for pneumococcal conjugate vaccine and influenza vaccine were Chinese Yuan 200 and 60 (10 US Dollars). 92% and 55% of respondents, respectively were not willing to pay the market price for these two vaccines. Lower price barrier and higher ability to pay were associated with higher WTP. Those with better vaccine or disease-related knowledge, higher perceived vulnerability and severity of diseases were willing to pay more. However, perceived effectiveness and safety barriers to vaccination had no significant effects on the WTP. Recommendations from peers and healthcare providers increased the WTP. Fathers and grand parents of children had a higher WTP than their mothers. The WTP decreased with age, but was not affected by education and occupation.

Conclusions

The majority of individuals, in our study, were not willing to pay the market price for self-paid vaccines against high-burden diseases in China. The economic barriers to vaccination should therefore be removed to increase the demand. Region-specific information about disease burden, fiscal capacity and cost-effectiveness is important for the development of local financing policy in order to cover vaccination costs. Interventions targeting psychosocial factors, such as health education and communication with providers and peers, could also be effective in increasing the uptake of these vaccinations.     

Threats to the estimation of benefit: are preference elicitation methods accurate?

Stated preference methods are used to estimate the value that people place on health care. The data that emerges from these studies is used to guide health policy. However, relatively little is known about how individuals make decisions in a preference elicitation task. Two methods (willingness to pay and conjoint analysis) are considered within the context of the literature from psychology (and also environmental economics) regarding how people construct preferences, process information, and make decisions. There is substantial evidence that individuals employ heuristics (cognitive shortcuts) in order to simplify tasks they are presented with. The use of heuristics implies that people ignore much of the information they are presented with and make decisions which would not be considered rational in the economic sense. These stated preference methods assume that individuals trade between the different attributes of a good or service when making decisions - an assumption that other theories predict is wrong. The implications of this are discussed.     

Mothers’ Preferences and Willingness to Pay for Human Papillomavirus Vaccination for Their Daughters: A Discrete Choice Experiment in Hong Kong

Objectives

To determine the preference of mothers in Hong Kong and their willingness to pay (WTP) for human papillomavirus (HPV) vaccination for their daughters.

Parental acceptance of human papillomavirus (HPV) vaccination in Indonesia: a cross-sectional study

Background

Cervical cancer ranks the second most frequent cancer in Indonesian women. In Indonesia, human papillomavirus (HPV) vaccine acceptance has not been studied before.

Objective

To determine parental HPV vaccine acceptance in Indonesia, and factors that influence their decision. Factors include sociodemographic factors, knowledge of HPV, HPV vaccination and cervical cancer, health beliefs about cervical cancer, and attitudes towards vaccination in general.

Methods

746 parents, with at least 1 daughter aged 0-14, were interviewed using questionnaires based on published and adjusted interviews. Interviews were done in sub district public health centers, general governmental hospitals, and via house-visits, in 5 Indonesian provinces.

Results

Parental HPV vaccine acceptance was 96.1%. Logistic regression revealed that age, beliefs regarding cervical cancer, and attitudes towards vaccination in general were significantly associated with HPV vaccine acceptance. Of the participants, 66.0%, 16.6%, and 15.8% had heard about cervical cancer, HPV, and HPV vaccination respectively. The mean total knowledge score was 1.91(Standard Deviation 2.31) on a 0-8 scale. Health beliefs about cervical cancer and attitudes towards vaccination in general were positive. Participants named the high cost of the vaccine, fear for side-effects, and chosen vaccination locations as possible barriers towards HPV vaccine implementation.

Discussion

Parental HPV vaccine acceptance is high, but knowledge about HPV and cervical cancer is low. During HPV vaccination programs, focus should not only be on providing information, but also on existing beliefs and attitudes towards cervical cancer and vaccination in general. If HPV vaccination programs were to be implemented in Indonesia, the indicated barriers should be taken into account.     

深圳地区女性流动人群HPV预防性疫苗接种意愿调查及影响因素分析

目的 了解深圳地区女性流动人群对HPV及其疫苗的认知情况及疫苗接种意愿和相关影响因素。方法 于2015年1-6月在深圳市10个行政区各社康中心对21～60岁女性流动人群进行问卷调查,采用非条件logistic回归模型分析HPV疫苗接种意愿的影响因素。结果 本次调查的969名女性流动人群平均年龄为（35.34±8.21）岁,仅有283人（29.2%）听说过人乳头瘤病毒,但548人（56.6%）愿意接种HPV预防性疫苗。不愿意接种的主要原因有:“担心疫苗的安全性”（34.7%）、“疫苗还没有大面积推广”（17.8%）、“疫苗的价格问题”（11.4%）、“对疫苗的效果不信任”（9.7%）、“认为没有患子宫颈癌的危险”（9.7%）及“已经有性生活,接种与否没有什么不同”（8.3%）。多因素logistic回归分析显示,中部地区（OR = 1.537,95%CI:1.034～2.286）和东部地区（OR = 2.252,95%CI:1.641～3.091）、汉族（OR = 1.698,95%CI:1.018～2.832）、高中及以上学历（OR = 2.150,95%CI:1.345～3.437)、近6个月性伴数为2个及以上（OR = 2.019,95%CI:1.105～3.689)的妇女对HPV疫苗接种意愿更高。结论 深圳地区女性流动人群HPV及其疫苗知晓率较低,接种意愿相对较高。地区、民族、受教育程度、性伴数量是影响女性流动人群HPV疫苗接种意愿的相关因素。     

Does Attribute Framing in Discrete Choice Experiments Influence Willingness to Pay? Results from a Discrete Choice Experiment in Screening for Colorectal Cancer

Objective:  Recent reviews of discrete choice methodology identified methodological issues warranting further exploration, including the issue of "framing." The objective of this study was to conduct a methodological exploration of the effect of attribute framing on marginal rates of substitution (MRS), including willingness to pay (WTP) from a discrete choice experiment (DCE), within the context of colorectal cancer screening preferences.
Methods:  The survey, a fractional factorial design of a two-alternative, unlabeled experiment, was mailed to a sample of 1920 subjects in NSW, Australia. Participants were randomized to one of four alternative "frames" of information. Attributes included: accuracy of the test for finding cancers, accuracy of the test for finding large polyps, how good the test is at saying you don't have cancer, cost, dietary and medication restrictions and sample collection. A mixed logit model was used to estimate preferences; MRS between attributes, including WTP, was calculated.
Results:  A total of 1157 surveys from 1920 (60.2%) were returned. Accuracy of the test for finding cancer was most likely to influence choice of test, followed by accuracy of the test for finding large polyps. Under some circumstances, framing of the attributes (e.g., cancers found vs. cancers missed) influenced the relative importance of attributes. Attribute framing significantly influenced estimates of WTP, and benefit: harm trade-offs that were calculated from MRS.
Conclusions:  Attribute framing can influence willingness to pay and benefit: harm trade-offs from DCEs. Appropriate design and analysis methods should be explored to further characterize the influence and extent of framing in discrete choice studies.     

HPV vaccines to prevent cervical cancer and genital warts: an update

Cervical cancer is an important public health problem worldwide, and especially in developing countries. The link between cervical cancer and oncogenic human papillomavirus (HPV) infection has been clearly established. Furthermore, non-oncogenic HPV are responsible for the majority of genital warts. Two prophylactic HPV vaccines are available, which have the potential of considerably reducing HPV-related morbidity and mortality. Both vaccines are based on virus-like particles of the L1 capsid protein, and are highly efficacious and immunogenic if given before exposure to HPV, i.e. to adolescent girls between 9 and 13 years of age in a three-dose schedule. This review describes the immunology of natural HPV infections and the immune response evoked through vaccination. The current duration of protection is 8.4 years with the bivalent vaccine (HPV16/18) and 5 years with the quadrivalent vaccine (HPV6/11/16/18). Research is on-going to evaluate the efficacy of the current vaccines in a two-dose schedule, as compared to the recommended three-dose schedule. To increase the protection, the development and testing of a nine-valent prophylactic HPV vaccine (HPV6/11/16/18/31/33/45/52/58) is being undertaken. Research is also directed towards therapeutic vaccines and the development of a prophylactic L2 vaccine.     

The role of heterogeneity of patients’ preferences in kidney transplantation

We elicit time and risk preferences for kidney transplantation from the entire population of patients of the largest Italian transplant centre using a discrete choice experiment (DCE). We measure patients’ willingness-to-wait (WTW) for receiving a kidney with one-year longer expected graft survival, or a low risk of complication. Using a mixed logit in WTW-space model, we find heterogeneity in patients’ preferences. Our model allows WTW to vary with patients’ age and duration of dialysis. The results suggest that WTW correlates with age and duration of dialysis, and that accounting for patients’ preferences in the design of kidney allocation protocols could increase their welfare. The implication for transplant practice is that eliciting patients’ preferences could help in the allocation of “non-ideal” kidneys.     

Consumer preferences for household water treatment products in Andhra Pradesh, India

Over 5 billion people worldwide are exposed to unsafe water. Given the obstacles to ensuring sustainable improvements in water supply infrastructure and the unhygienic handling of water after collection, household water treatment and storage (HWTS) products have been viewed as important mechanisms for increasing access to safe water. Although studies have shown that HWTS technologies can reduce the likelihood of diarrheal illness by about 30%, levels of adoption and continued use remain low. An understanding of household preferences for HWTS products can be used to create demand through effective product positioning and social marketing, and ultimately improve and ensure commercial sustainability and scalability of these products. However, there has been little systematic research on consumer preferences for HWTS products.     

Willingness to pay for dental fear treatment

The aim of this paper is to discuss the social desirability of supplying dental fear treatment in addition to dental treatment using the results from a treatment programme for patients with severe dental fear. The programme consisted of three different dental fear treatments: Cognitive therapy, applied relaxation and nitrous oxide sedation, in addition to dental treatment. To evaluate the effects of uncertainty on the patients' benefits from the programme, we elicited their willingness to pay, both before and after receiving treatment, since we expected patients to be uncertain about the outcome of the dental fear treatment. We found that the social desirability of the treatment was very sensitive to uncertainty. While only 24% of the patients were willing to pay the actual cost of the treatment before attending, 71% were willing to pay afterwards. This implies that many patients who would benefit from the treatment ex post are not willing to pay the cost of the treatment ex ante, and will thus not receive any treatment unless it is subsidized.     

Trying to estimate a monetary value for the QALY

In this paper we study the feasibility of estimating a monetary value for a QALY (MVQ). Using two different surveys of the Spanish population (total n = 892), we consider whether willingness to pay (WTP) is (approximately) proportional to the health gains measured in QALYs. We also explore whether subjects’ responses are prone to any significant biases. We find that the estimated MVQ varies inversely with the magnitude of health gain. We also find two other (ir)regularities: the existence of ordering effects; and insensitivity of WTP to the duration of the period of payment. Taken together, these effects result in large variations in estimates of the MVQ. If we are ever to obtain consistent and stable estimates, we should try to understand better the sources of variability found in the course of this study.     

Discrete choice experiments in health economics

One method that is increasingly being used in health economics to elicit stated preferences concerning health matters is the discrete choice experiment (DCE). This editorial explores four sets of issues facing researchers who wish to employ DCE techniques: (a) normative issues about how data from DCE studies might be used to inform policy, (b) psychological issues concerning the meaningfulness of the data generated, (d) technical issues relating to how the data are generated and (d) issues relating to the generalisability of the data from DCE studies. Given current uncertainties surrounding these issues, it is our view that more caution and greater circumspection towards DCE is appropriate at this stage.