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

Maximum Acceptable Risk Estimation Based on a Discrete Choice Experiment and a Probabilistic Threshold Technique

OBJECTIVE

We aimed to empirically compare maximum acceptable risk results estimated using both a discrete choice experiment (DCE) and a probabilistic threshold technique (PTT).

METHODS

Members of the UK general public (n = 982) completed an online survey including a DCE and a PTT (in random order) measuring their preferences for preventative treatment for rheumatoid arthritis. For the DCE, a Bayesian D-efficient design consisting of four blocks of 15 choice tasks was constructed including six attributes with varying levels. The PTT used identical risk and benefit attributes. For the DCE, a panel mixed-logit model was conducted, both mean and individual estimates were used to calculate maximum acceptable risk. For the PTT, interval regression was used to calculate maximum acceptable risk. Perceived complexity of the choice tasks and preference heterogeneity were investigated for both methods.

RESULTS

Maximum acceptable risk confidence intervals of both methods overlapped for serious infection and serious side effects but not for mild side effects (maximum acceptable risk was 32.7 percent-points lower in the PTT). Although, both DCE and PTT tasks overall were considered easy or very easy to understand and answer, significantly more respondents rated the DCE choice tasks as easier to understand compared with those who rated the PTT as easier (7-percentage point difference; p < 0.05).

CONCLUSIONS

Maximum acceptable risk estimate confidence intervals based on a DCE and a PTT overlapped for two out of the three included risk attributes. More respondents rated the DCE as easier to understand. This may suggest that the DCE is better suited in studies estimating maximum acceptable risk for multiple risk attributes of differing severity, while the PTT may be better suited when measuring heterogeneity in maximum acceptable risk estimates or when investigating one or more serious adverse events.

Patients' preferences in dental care: A discrete-choice experiment and an analysis of willingness-to-pay

INTRODUCTION

Dental diseases are a major problem worldwide. Costs are a burden on healthcare systems and patients. Missed treatments can have health and financial consequences. Compared to other health services, dental treatments are only covered in parts by statutory health insurance (SHI). Using the example of dental crowns for a cost-intensive treatment, our study aims to investigate whether (1) certain treatment attributes determine patients' treatment choice, and (2) out-of-pocket payments represent a barrier to access dental care.

METHODS

We conducted a discrete-choice-experiment by mailing questionnaires to 10,752 people in Germany. In presented scenarios the participants could choose between treatment options (A, B, or none) composed of treatment attribute levels (e.g., color of teeth) for posterior (PT) and anterior teeth (AT). Considering interaction effects, we used a D-efficient fractional factorial design. Choice analysis was performed using different models. Furthermore, we analyzed willingness-to-pay (WTP), preference of choosing no and SHI standard care treatment, and influence of socioeconomic characteristics on individual WTP.

RESULTS

Out of n = 762 returned questionnaires (response rate of r = 7.1), n = 380 were included in the analysis. Most of the participants are in age group "50 to 59 years" (n = 103, 27.1%) and female (n = 249, 65.5%). The participants' benefit allocations varied across treatment attributes. Aesthetics and durability of dental crowns play most important roles in decision-making. WTP regarding natural color teeth is higher than standard SHI out-of-pocket payment. Estimations for AT dominate. For both tooth areas, "no treatment" was a frequent choice (PT: 25.7%, AT: 37.2%). Especially for AT, treatment beyond SHI standard care was often chosen (49.8%, PT: 31.3%). Age, gender, and incentive measures (bonus booklet) influenced WTP per participant.

CONCLUSION

This study provides important insights into patient preferences for dental crown treatment in Germany. For our participants, aesthetic for AT and PT as well as out-of-pocket payments for PT play an important role in decision-making. Overall, they are willing to pay more than the current out-of-pockt payments for what they consider to be better crown treatments. Findings may be valuable for policy makers in developing measures that better match patient preferences.

Conjoint analyses of patients’ preferences for primary care: a systematic review

Background

While patients’ preferences in primary care have been examined in numerous conjoint analyses, there has been little systematic effort to synthesise the findings. This review aimed to identify, to organise and to assess the strength of evidence for the attributes and factors associated with preference heterogeneity in conjoint analyses for primary care outpatient visits.

Methods

We searched five bibliographic databases (PubMed, Embase, PsycINFO, Econlit and Scopus) from inception until 15 December 2021, complemented by hand-searching. We included conjoint analyses for primary care outpatient visits. Two reviewers independently screened papers for inclusion and assessed the quality of all included studies using the checklist by ISPOR Task Force for Conjoint Analysis. We categorized the attributes of primary care based on Primary Care Monitoring System framework and factors based on Andersen’s Behavioural Model of Health Services Use. We then assessed the strength of evidence and direction of preference for the attributes of primary care, and factors affecting preference heterogeneity based on study quality and consistency in findings.

Results

Of 35 included studies, most (82.4%) were performed in high-income countries. Each study examined 3–8 attributes, mainly identified through literature reviews (n = 25). Only six examined visits for chronic conditions, with the rest on acute or non-specific / other conditions. Process attributes were more commonly examined than structure or outcome attributes. The three most commonly examined attributes were waiting time for appointment, out-of-pocket costs and ability to choose the providers they see. We identified 24/58 attributes with strong or moderate evidence of association with primary care uptake (e.g., various waiting times, out-of-pocket costs) and 4/43 factors with strong evidence of affecting preference heterogeneity (e.g., age, gender).

Conclusions

We found 35 conjoint analyses examining 58 attributes of primary care and 43 factors that potentially affect the preference of these attributes. The attributes and factors, stratified into evidence levels based on study quality and consistency, can guide the design of research or policies to improve patients’ uptake of primary care. We recommend future conjoint analyses to specify the types of visits and to define their attributes clearly, to facilitate consistent understanding among respondents and the design of interventions targeting them.

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Trial registration

On Open Science Framework: https://osf.io/m7ts9

Patient Preference for Self-Injection Devices in Rheumatoid Arthritis: A Discrete Choice Experiment in China

Objective

Rheumatoid arthritis (RA) is increasingly treated with biologics, which is commonly administered by injection devices. The aim of this study is to evaluate patients' preferences for self-injection devices in RA, and to elicit their willingness to pay (WTP) for injector devices in China.

Methods

RA patients were recruited from Beijing, Shanghai, Guangzhou, Chengdu, Wuhan and Xi'an in China. A discrete choice experiment (DCE) was employed to elicit patient preferences. Patients were presented with 15 choice sets that consisted of seven attributes, which were developed based on literature review and further validated by physicians. The seven attributes were as follows: operation steps, injection pain, feedback indication, needle visibility, needle protection, size and out-of-pocket costs. A mixed logit model was used to analyze the relative importance of seven attributes and to calculate the WTP for a changed attribute level.

Results

Analyses included 114 adults with RA (mean age of 44.6 years old). When choosing the injection device, all attributes had significant influence. Among nonmonetary attributes, very slight injection pain was the most preferred for patients, followed by auto-injection method, thicker size, hidden needle, with needle protection and multiple feedback indication. Patients had a negative preference for increasing out-of-pocket costs. Patients were willing to pay CNY 45.26 for improving slight injection pain to very slight injection pain, CNY 13.26 for the auto-injection method, CNY 12.22 for the thicker size, CNY 10.06 for the hidden needle, CNY 9.82 for needle protection, and CNY 9.70 for multiple feedback indicators.

Conclusion

The results suggested that injection pain was the most important attribute for RA patients. Meanwhile, all other enhanced attributes of self-injection devices also significantly influence patients' selection on injection devices. Findings suggested that there is significant potential value in developing self-injection devices that could further help improve treatment adherence and promote patient-centered care in autoimmune diseases.

The Value of Genomic Testing: A Contingent Valuation Across Six Child- and Adult-Onset Genetic Conditions

OBJECTIVES

The aim of this study was to elicit the willingness-to-pay (WTP) for genomic testing, using contingent valuation, among people with lived experience of genetic conditions in Australia.

METHODS

Parents of children with suspected mitochondrial disorders, epileptic encephalopathy, leukodystrophy, or malformations of cortical development completed a dynamic triple-bounded dichotomous choice (DC) contingent valuation. Adult patients or parents of children with suspected genetic kidney disease or complex neurological and neurodegenerative conditions completed a payment card (PC) contingent valuation. DC data were analyzed using a multilevel interval regression and a multilevel probit model. PC data were analyzed using a Heckman selection model.

RESULTS

In total, 360 individuals participated in the contingent valuation (CV), with 141 (39%) and 219 (61%) completing the DC and PC questions, respectively. The mean WTP for genomic testing was estimated at AU$2830 (95% confidence interval [CI] 2236-3424) based on the DC data and AU$1914 (95% CI 1532-2296) based on the PC data. The mean WTP across the six cohorts ranged from AU$1879 (genetic kidney disease) to AU$4554 (leukodystrophy).

CONCLUSIONS

Genomic testing is highly valued by people experiencing rare genetic conditions. Our findings can inform cost-benefit analyses and the prioritization of genomics into mainstream clinical care. While our WTP estimates for adult-onset genetic conditions aligned with estimates derived from discrete choice experiments (DCEs), for childhood-onset conditions our estimates were significantly lower. Research is urgently required to directly compare, and critically evaluate, the performance of CV and DCE methods.

Willingness to Pay for Improved Operations and Maintenance Services of Gravity-Fed Water Schemes in Idjwi Island (Democratic Republic of the Congo)

Developing understanding of the economic value that communities ascribe to improved operations and maintenance (O&M) services has emerged as a key factor in achieving financial sustainability for rural water systems. The present study elicits household willingness to pay (WTP) for improved O&M services in eight gravity-fed water schemes in Idjwi Island (Democratic Republic of the Congo, DRC). A contingent valuation survey was implemented through an open-ended format questionnaire to 1105 heads of household and a log-linear regression model was employed to assess the factors influencing higher values. Findings show an average willingness to pay of 327 Congolese Francs (CDF) per month and 36 CDF per bucket. Results also indicate a significant WTP differential among studied schemes. The analysis of the conditioning factors reveals that the level of excludability, the participation in management meetings and the time employed in fetching water from an improved source are contingent with their WTP. The findings of this study are important for development agents trying to establish acceptable, affordable and practicable tariffs that help finance reliable rural water systems in Idjwi.

Text messaging and financial incentives to encourage weight loss in men with obesity: the Game of Stones feasibility RCT

Background

In 2016, 26% of UK men were estimated to be obese. Systematic reviews suggest that few men engage in formal weight loss interventions that support weight reduction and improve health.

Objective

To co-produce, with patient and public involvement, an acceptable and feasible randomised controlled trial design to test a men-only weight management intervention.

Design

This was a two-phase feasibility study. Phase 1 was the development of intervention components, study procedures and materials including a discrete choice experiment with survey questions. Phase 2 was an individually randomised three-arm feasibility trial over 12 months. Qualitative interviews were conducted at 3 and 12 months.

Setting

The setting was two sites in Scotland that had disadvantaged urban and rural areas and differed in employment levels and ethnic groups.

Participants

In phase 1, 1045 men with obesity were recruited by Ipsos MORI (London, UK; www.ipsos.com/ipsos-mori/en-uk) to represent the UK population. In phase 2, 105 men with obesity were recruited in the community or through general practice obesity registers. Qualitative interviews were conducted with 50 men at 3 months and with 33 men at 12 months.

Interventions

The trial arms were narrative short message service (SMS) for 12 months (SMS only), financial endowment incentive informed by loss aversion and linked to achievement of weight loss targets plus narrative SMS for 12 months (SMS + I), and waiting list control group for 12 months followed by 3 months of an alternative SMS style developed based on feedback from men who had received the narrative SMS (control).

Main outcome measures

The main outcome measures were acceptability and feasibility of recruitment, retention, engagement, intervention components and trial procedures. Outcomes were assessed by examining procedural, quantitative and qualitative data at 3, 6 and 12 months.

Results

The most acceptable incentive strategy, based on the discrete choice experiment results, was to verify weight loss of 5% at 3 months, verify weight loss of 10% at 6 months and maintain weight loss of 10% at 12 months. Overall, 105 men with obesity from across the socioeconomic spectrum were successfully recruited to target, 59% of whom lived in more disadvantaged areas. Retention at 12 months was acceptable (74%) and was higher among individuals from disadvantaged areas. Narrative SMS were acceptable to many men, with a minority reporting negative reactions. Incentives were acceptable but were not the primary motivation for behaviour change. Twelve men in the incentive arm (33%) secured at least some money and three (8%) secured the full amount. Both intervention arms lost some weight, with greater weight loss in the arm that received SMS and incentives. The alternative SMS based on men’s feedback received no strong negative reactions.

Limitations

Fewer participants from the SMS + I arm (64%) completed the study at 12 months than did those in the SMS-only (79%) and control (83%) arms. The reasons for this difference were complex.

Conclusions

The men-only weight management intervention consisting of narrative SMS and financial incentives was acceptable and feasible, meeting the progression criteria for a full trial. Tailoring of SMS may improve acceptability and retention.

Future work

Minor refinements to the intervention components based on the study findings will be made prior to testing in a multisite definitive randomised controlled trial.

Trial registration

ClinicalTrials.gov NCT03040518.

Funding

This project was funded by the National Institute for Health Research (NIHR) Public Health Research programme and will be published in full in Public Health Research; Vol. 8, No. 11. See the NIHR Journals Library website for further project information.

Reliability and Validity of the Contingent Valuation Method for Estimating Willingness to Pay: A Case of In Vitro Fertilisation

BACKGROUND

The contingent valuation (CV) method is an alternative approach to typical health economic methods for valuing interventions that have both health and non-health outcomes. Fertility treatment, such as in vitro fertilisation (IVF), fall into this category because of the significant non-health outcomes associated with having children.

AIM

To estimate the general population's willingness to pay (WTP) for one cycle of IVF and one year of IVF treatment, and to test the reliability and validity of a CV instrument.

METHODS

Three online CV surveys were administered to a total of 1870 participants from the Australian general population using an ex-post perspective, that is, they assumed they were infertile and needed IVF to conceive a child. Participants answered questions with starting point WTP bids of 2018 Australian dollars (AU$) 4000 or $10,000 for the cost of one IVF cycle, and treatment success rates of 10%, 20% and 50% per IVF cycle. Tests for reliability, internal construct validity, starting point bias, and external validity were performed.

RESULTS

Depending on the success rate and the starting point WTP bid, the mean WTP for one IVF cycle ranged from $6135 to $13,561, while the mean WTP for one year of IVF treatment varied from $17,080 to $31,006. The CV method was reliable and satisfied internal construct and external criterion validity. However strong starting point bias was evident, rendering the mean WTP values highly imprecise.

CONCLUSION

The CV method holds promise for eliciting the value of interventions, such as fertility treatment, that have significant health and non-health outcomes. Survey instruments that prevent starting point bias are essential. Comparing the results of CV methods to other value elicitation methods is needed to confirm convergent validity.

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

BACKGROUND

Vaccination 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.

OBJECTIVE

The 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.

METHODS

In 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.

RESULTS

The 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 5years to 20years, 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.

CONCLUSIONS

Adults 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.

Modelling Nonlinearities and Reference Dependence in General Practitioners' Income Preferences

This paper tests for the existence of nonlinearity and reference dependence in income preferences for general practitioners. Confirming the theory of reference dependent utility within the context of a discrete choice experiment, we find that losses loom larger than gains in income for Norwegian general practitioners, i.e. they value losses from their current income level around three times higher than the equivalent gains. Our results are validated by comparison with equivalent contingent valuation values for marginal willingness to pay and marginal willingness to accept compensation for changes in job characteristics. Physicians' income preferences determine the effectiveness of 'pay for performance' and other incentive schemes. Our results may explain the relative ineffectiveness of financial incentive schemes that rely on increasing physicians' incomes. Copyright © 2015 John Wiley & Sons, Ltd.

Empirical Testing of the External Validity of a Discrete Choice Experiment to Determine Preferred Treatment Option: The Case of Sleep Apnea

There is an increasing use of the discrete choice experiment (DCE) method in health care to estimate preferences of individuals and the public for different services. Despite this increasing use, there are few studies that investigate the validity of the DCE in health. This study investigates the external validity of DCE by comparing the predicted treatment choices from the DCE to the actual treatment choices made by the same respondents using a decision board (DB) approach. The sample includes 140 patients who came for a sleep apnea routine visit in a hospital setting. Each respondent answered 10 DCE tasks and 1 DB task. The preferences were estimated with a generalized multinomial logit model and the predicted and actual treatment choices were compared both at the sample and individual levels. The results raise questions about the external validity of DCE in health. At the sample level, the comparison showed large but not significant differences between the two methods. This can be explained in part by the aggregation process that obscures variability in the individuals' preferences. At the individual level, the comparison showed that the two methods led to significantly different patterns of choices.

What is the value given by consumers to nutritional label information? Results from a large investigation in Europe

RATIONALE

Nutrition labels on prepackaged foods have been widely advocated as a medium to foster healthier eating habits in the general population.

OBJECTIVE

The study is aimed at understanding how people value nutritional information on food labels, in particular for front-of-pack labeling.

METHODS

A phone-assisted survey of 7550 consumers in 16 European countries was conducted. People were asked about their opinion on nutritional information provided at different levels, from the media to public institutions, and their commitment to healthy behavior. The value of pack labeling was estimated using a willingness-to-pay (WTP) elicitation technique.

RESULTS

Older age groups (>45 years old), members of a larger family, people of low income or low education, and those who perceived themselves to be obese valued front-of-pack nutritional labeling. WTP estimates across all countries provided an average accepted added price of $4.32 to the overall yearly food expenditure (95% confidence interval, 3.33-3.68).

CONCLUSIONS

Overall, perceived value of labeling is low. However, factors affecting the value for consumer of nutritional labeling appear to be strictly linked to the socioeconomic and health status of the respondents.

Depressive symptoms and posttraumatic stress disorder as determinants of preference weights for attributes of obstetric care among Ethiopian women

Background

Mental health, specifically mood/anxiety disorders, may be associated with value for health care attributes, but the association remains unclear. Examining the relation between mental health and attributes in a context where quality of care is low and exposure to suboptimal health conditions is increased, such as in Sub Saharan Africa (SSA), may elucidate the association.

Methodology/Principal Findings

We assessed whether preference weights for obstetric care attributes varied by mental health among 1006 women from Jimma Zone, Ethiopia, using estimates obtained through a discrete choice experiment (DCE), a method used to elicit preferences. Facilities were described by several attributes including provider attitude and performance and drug/equipment availability. Mental health measures included depressive symptoms and posttraumatic stress disorder (PTSD). We used Bayesian models to estimate preference weights for attributes and linear models to investigate whether these weights were associated with mental health. We found that women with high depressive symptoms valued a positive provider attitude [β = −0.43 (95% CI: −0.66, −0.21)] and drug/equipment availability [β = −0.43 (95% CI: −0.78, −0.07)] less compared to women without high depressive symptoms. Similar results were obtained for PTSD. Upon adjusting for both conditions, value for drug/equipment availability was lower only among women with both conditions [β = −0.89 (95% CI −1.4, −0.42)].

Conclusions/Significance

We found that women with psychopathology had lower preference weights for positive provider attitude and drug/equipment availability. Further work investigating why value for obstetric care attributes might vary by psychopathology in SSA is needed.

Eliciting willingness to pay in obstetrics: comparing a direct and an indirect valuation method for complex health outcomes

OBJECTIVE

To compare direct and indirect willingness to pay (WTP) elicitation methods in terms of feasibility, reliability, and comparability. The application is obstetrics, where always both a mother's and a child's health are at stake.

METHODS

An open-ended contingent valuation method (CVM) as a direct WTP elicitation method, and the discrete choice experiment (DCE) as an indirect WTP elicitation method. Vignettes to be valued were based on clinical patient data. Participants were 88 laypersons who received their questionnaires by postal mail.

RESULTS

The DCE task was completed faster (p=0.006) and was regarded easier (p<0.001) than the CVM task. Test-retest for CVM was substantial (ICC=0.76), and for DCE moderate (k=0.49). Female sex (p<0.001), age≥50 years (p=0.013), higher income (p<0.001), and higher education (p<0.001) were associated with higher WTP. Correlation between CVM and DCE was 0.79 (Kendall's Tau-b; p<0.001). The implied WTP as derived with DCE was between 2.3 and 10.2 times higher than with CVM. The relationship between the WTPs was linear.

CONCLUSION

It is yet unclear what lies behind the numbers of DCE. DCE has no methodological benefits over the conventional CVM when eliciting WTP for complex health outcomes in obstetrics.

Patient preference for latent tuberculosis infection preventive treatment: a discrete choice experiment

OBJECTIVES

To quantify patient preferences when making decisions as to whether to accept latent tuberculosis infection (LTBI) preventive treatment, using a discrete choice experiment (DCE).

METHODS

A DCE survey was developed and administered to LTBI patients. Each patient was given 10 random choices along with two fixed choices to check consistency. Two hypothetical treatment options and one opt-out option were presented in each choice task. Latent class analysis was conducted to estimate preferences for six key treatment attributes.

RESULTS

Among the 214 respondents, 194 (90.7%) who provided valid DCE responses and complete sociodemographic information were included. Results consistently suggested that respondents were averse to higher risk of active tuberculosis and side effects and longer treatment. A three-latent-class model with five covariates was chosen. Forty-seven percent of the respondents were assigned to class 1, 32% to class 2, and 21% to class 3. Although all six attributes were shown to significantly influence the respondents' treatment decision, the risk of active tuberculosis, chance of liver damage, and frequency of clinic visits were the most important ones. Significant preference heterogeneity was observed in two attributes: frequency of clinic visits (P < 0.01) and chance of liver damage developing (P < 0.01). Class 1 individuals were most likely to have children. Class 2 had the highest employment rate. Class 3 respondents tended to choose the opt-out option on DCE tasks and were more likely to be born outside Canada, have higher education, and be unemployed.

CONCLUSION

Respondents consistently preferred preventive treatment with higher effectiveness, fewer side effects, and shorter length. Substantial preference heterogeneity existed among respondents.

Girls' preferences for HPV vaccination: a discrete choice experiment

A discrete choice experiment was developed to investigate if girls aged 12-16 years make trade-offs between various aspects of human papillomavirus (HPV) vaccination, and to elicit the relative weight that girls' place on these characteristics. Degree of protection against cervical cancer, protection duration, risk of side-effects, and age of vaccination, all proved to influence girls' preferences for HPV vaccination. We found that girls were willing to trade-off 38% protection against cervical cancer to obtain a lifetime protection instead of a protection duration of 6 years, or 17% to obtain an HPV vaccination with a 1 per 750,000 instead of 1 per 150,000 risk of serious side-effects. We conclude that girls indeed made a trade-off between degree of protection and other vaccine characteristics, and that uptake of HPV vaccination may change considerably if girls are supplied with new evidence-based information about the degree of protection against cervical cancer, the protection duration, and the risk of serious side-effects.