Valuing outcomes in health care: a comparison of willingness to pay and quality-adjusted life-years

Can we estimate the ‘social’ value of a QALY?

There is growing interest in estimating the 'societal' willingness to pay (WTP) for a quality adjusted life year (QALY) to help public health system decision-makers determine whether a health care programme should/not be undertaken. However, there is a lack of clarity in this debate concerning four core issues: (i) is 'social' WTP simply the sum of 'individual' WTP; (ii) will 'individual' WTP map directly into 'social' WTP; (iii) is 'personal' income the appropriate budget constraint; (iv) should WTP be adjusted for ability to pay? This paper outlines the relevance and importance of each of these issues in the hope of encouraging a wider debate on the core issues that empirical studies will have to explore to discover whether such a value may be obtained.

Quality-adjusted life years was a poor predictor of women's willingness to pay in acute and chronic conditions: results of a survey

OBJECTIVE

We investigated the relationship between quality-adjusted life years (QALYs) and willingness to pay (WTP) in acute and chronic conditions.

STUDY DESIGN AND SETTING

Face-to-face interviews were used to collect data in a convenience sample of women. Participants completed one interview evaluating preferences for an acute condition, post-chemotherapy nausea and vomiting (PCNV), and the other interview for a chronic condition (breast cancer). Preferences were elicited for QALYs using visual analogue scale (VAS), and standard gamble in addition to WTP. Because QALYs and WTP are purportedly based on the same underlying theoretical foundations, WTP was regressed onto change in QALYs, age, income, and health status.

RESULTS

Regression analysis reported statistically significant models for all breast cancer (P < .001) and PCNV (P < .05) conditions tested. However, QALY was not a significant predictor of WTP.

CONCLUSION

The results of this study indicate QALYs was a poor predictor of WTP for the conditions tested. Linear combinations of change in QALYs, age, income, and health status were a better predictor of WTP for chronic than acute conditions. This can be attributed to violations of underlying assumptions in measurement of QALYs with acute conditions and to problems with the use of WTP with chronic conditions.

Impact of indinavir on the quality of life in patients with advanced HIV infection treated with zidovudine and lamivudine

OBJECTIVE

In AIDS Clinical Trial Group (ACTG) study 320, triple-combination antiretroviral therapy including indinavir significantly slowed progression to acquired immunodeficiency syndrome or death, compared with treatment with dual nucleoside reverse-transcriptase inhibitors (NRTIs) alone, in zidovudine-experienced patients with advanced human immunodeficiency virus (HIV) infection. We examined the impact of indinavir on quality of life in participants from this study.

METHODS

A total of 1156 protease inhibitor- and lamivudine-naive patients stratified by CD4 cell count (<or=50 and 51-200 cells/mm(3)) were randomized to receive zidovudine (or stavudine) and lamivudine, with or without indinavir. Health-related quality of life was measured using the ACTG QoL601-602 questionnaire, which assesses general health status measured on a visual analogue scale and 8 specific health-related domains. Quality-adjusted survival time was estimated using the visual analogue scale for general health.

RESULTS

Mean changes in general health scores after 24 weeks were +2.9 in the triple-therapy group versus -0.2 in the dual-therapy group (P=.018). By week 24, scores in all specific domains were higher with triple-drug therapy than dual-drug therapy, with statistically significant differences in role function, energy, and pain scores. Benefits of triple-drug therapy were largely confined to patients with CD4 cell counts of <or=50 cells/mm(3). Quality-adjusted survival time did not differ significantly between the 2 treatment groups.

CONCLUSIONS

Triple-drug therapy with indinavir and 2 NRTIs resulted in a significant improvement in general health status after 24 weeks, especially in patients with low CD4 cell counts. Patients receiving triple-drug therapy also had significantly better role function, energy, and pain scores than did patients treated with dual-drug therapy.

How do Zimbabweans value health states?

BACKGROUND: Quality of life weights based on valuations of health states are often used in cost utility analysis and population health measures. This paper reports on an attempt to develop quality of life weights within the Zimbabwe context. METHODS: 2,384 residents in randomly selected small residential plots of land in a high-density suburb of Harare valued descriptors of 38 health states based on different combinations of the five domains of the EQ-5D (mobility, self-care, usual activities, pain or discomfort and anxiety or depression). The English version of the EQ-5D was used. The time trade-off method was used to determine the values, and 19,020 individual preferences for health states were analysed. A residual maximum likelihood linear mixed model was used to estimate a function for predicting the values of all possible combinations of levels on the five domains. The model was fit to a random subset of two-thirds of the observations, with the remaining observations reserved for analysis of predictive validity. The results were compared to a similar study undertaken in the United Kingdom. RESULTS: A credible model was developed to predict the values of states that were not valued directly. In the subset of observations reserved for validation, the mean absolute difference between predicted and observed values was 0.045. All domains of the EQ-5D were found to contribute significantly to the model, both at the moderate and severe levels. Severe pain was found to have the largest negative coefficient, followed by the inability to wash and dress oneself. CONCLUSION: Despite a generally lower education level than their European counterparts, urban Zimbabweans appear to value health states in a consistent manner, and the determination of a global method of establishing quality of life weights may be feasible and valid. However, as the relative weightings of the different domains, although correlated, differed from the standard set of weights recommended by the EuroQol Group, the locally determined coefficients should be used within the Zimbabwean context.

Willingness-to-pay for community-based insurance in Burkina Faso

PURPOSE

To study the willingness-to-pay (WTP) for a proposed community-based health insurance (CBI) scheme in order to provide information about the relationship between the premium that is required to cover the costs of the scheme and expected insurance enrollment levels. In addition, factors that influence WTP were to be identified.

METHODS

Data were collected from a household survey using a two-stage cluster sampling approach, with each household having the same probability of being selected. Interviews were conducted with 2414 individuals and 705 household heads. The take-it-or-leave-it (TIOLI) and the bidding game were used to elicit WTP.

RESULTS

The average individual was willing to pay 2384 (elicited by the TIOLI) or 3191 (elicited by the bidding game) CFA (3.17 US dollars or 4.25 US dollars) to join CBI for him/herself. The head of household agreed to pay from 6448 (elicited by the TIOLI) or 9769 (elicited by the bidding game) CFA (8.6 US dollars or 13.03 US dollars) to join the health insurance scheme for his/her household. These results were influenced by household and individual ability-to-pay, household and individual characteristics, such as age, sex and education. The two methods yielded similar patterns of estimated WTP, in that higher WTP was obtained for higher income level, higher previous medical expenditure, higher education, younger people and males. A starting point bias was found in the case of the bidding game.

CONCLUSIONS

Both TIOLI and bidding game methods can elicit a value of WTP for CBI. The value elicited by the bidding game is higher than by the TIOLI, but the two approaches yielded similar patterns of estimated WTP. WTP information can be used for setting insurance premium. When setting the premiums, it is important to consider differences between the real market and the theoretical one, and between the WTP and the cost of benefits package. The beneficiaries of CBI should be enrolled at the level of households or villages in order to protect vulnerable groups such as women, elders and the poor.

Gender's effect on willingness-to-pay for community-based insurance in Burkina Faso

The purpose was to study gender's effect on willingness-to-pay (WTP) for community-based insurance (CBI) in order to provide information for deciding enrolment unit and setting premium in Burkina Faso. A two-stage cluster sampling was used in the household survey, with each household having the same probability of being selected. One thousand one hundred and seventy-eight men and 1236 women in the 800 households were interviewed. The bidding game approach was used to elicit WTP. We found that compared to male, female had less education, lower income and expenditure, less episodes of diseases and lower ratio of becoming household head, but higher marriage rate. These characteristics influenced the WTP difference between men and women. Men were willing to pay 3666 CFA ($4.89) to join CBI, 928 CFA higher than women were. Education and economic status positively influenced WTP, implying higher years of schooling and economic status and higher WTP. Age and distance to health facility negatively influenced WTP, thus higher age and longer distance and less WTP. Based on the results from this study, we suggest that CBI should be enrolled on the basis of households or villages in order to protect vulnerable persons, such as the aged, women and the poor. In setting premium a policy-maker needs to take into account costs of the CBI benefits package, possible subsidies from government and other agencies and WTP information. WTP should never be taken as a premium because it only provides some information for the respondents' financial acceptability for a certain benefits package.

The new subjective medicine: taking the patient's point of view on health care and health

Calls to respect patient autonomy and produce patient-centered outcomes have recently brought the patient's point of view back into the center of clinical medicine. Bioethics has argued that patient values must be respected in health care decisions. But it has generally not questioned medicine's goals, including its definition of health. For bioethics, health has remained an objective biological fact. However, pressures to improve the cost-effectiveness of medical care have increased interest in the subjective health and quality of life of patients. Perceived health, health-related quality of life, and health-state utilities bring health assessment progressively closer to the patient's perspective. Now even death's harm to patients is qualified by the value patients place on their health state. Medicine's epidemiological transition from acute to chronic disease is thus prompting an epistemological transition from primarily objective to primarily subjective evidence of health and health care effectiveness. Now some of the most important patient outcomes, like patient choices before them, are valid because they are subjective. Pathophysiology is appropriately becoming a means to produce health as it is defined from the patient's point of view. The physicians' job description will be changed to focus on patients' lives rather than patients' bodies. Definitive evaluations of medical effectiveness will occur within patients' lives rather than within doctors' hospitals. This further incorporation of patient subjectivity should carry us well beyond informed consent and the other protections for patient autonomy bequeathed to us by bioethics.

A utility-theoretic model for QALYs and willingness to pay

Despite the widespread use of quality-adjusted life years (QALY) in economic evaluation studies, their utility-theoretic foundation remains unclear. A model for preferences over health, money, and time is presented in this paper. Under the usual assumptions of the original QALY-model, an additive separable presentation of the utilities in different periods exists. In contrast to the usual assumption that QALY-weights do solely depend on aspects of health-related quality of life, wealth-standardized QALY-weights might vary with the wealth level in the presented extension of the original QALY-model resulting in an inconsistent measurement of QALYs. Further assumptions are presented to make the measurement of QALYs consistent with lifetime preferences over health and money. Even under these strict assumptions, QALYs and WTP (which also can be defined in this utility-theoretic model) are not equivalent preference-based measures of the effects of health technologies on an individual level. The results suggest that the individual WTP per QALY can depend on the magnitude of the QALY-gain as well as on the disease burden, when health influences the marginal utility of wealth. Further research seems to be indicated on this structural aspect of preferences over health and wealth and to quantify its impact.

iMPACT3: Internet-based development and administration of utility elicitation protocols

iMPACT3 (Internet Multimedia Preference Assessment Instrument Construction Tool, version 3) is a software development environment that helps researchers build Internet-capable multimedia utility elicitation software programs. The program is a free, openly accessible Web site (http.// preferences.ucsd.edu/impact3/asp). To develop a utility elicitation software program using iMPACT3, a researcher selects modular protocol components from a library and custom tailors the components to the details of his or her research protocol. iMPACT3 builds a Web site implementing the protocol and downloads it to the researcher's computer. In a study of 75 HIV-infected patients, an iMPACT3-generated protocol showed substantial evidence of construct validity and good internal consistency (logic error rates of 4% to 10% and procedural invariance error rates of 10% to 28%, depending on the elicitation method) but only fair 3- to 6-week test-retest reliability (intraclass correlation coefficient= 0.42 to 0.55). Further work may be needed on specific utility assessment procedures, but this study's results confirm iMPACT3's feasibility in facilitating the collection of health state utility data.

Costs of opioid therapy for chronic nonmalignant pain in Germany: an economic model comparing transdermal fentanyl (Durogesic) with controlled-release morphine

The fentanyl transdermal therapeutic system (fentanyl-TTS;Durogesic) has a distinct route of administration and safety profile compared with other opioids used in the treatment of moderate to severe pain.These aspects are likely to have an impact on patient acceptance and functioning as well as efficacy. We compared the cost-utility of fentanyl-TTS and controlled-release morphine (cr-morphine) in the treatment of moderate to severe nonmalignant pain in outpatients in Germany. A 1-year, three-phased decisionanalytic model was constructed, incorporating estimates of a variety of aspects of pain control.Use of fentanyl-TTS was predicted to incur higher costs than cr-morphine over 1 year of treatment (DM 6950 vs.DM 6186, respectively) but was associated with a higher number of quality-adjusted life days (234 vs. 216, respectively), thus achieving an incremental cost-utility ratio of DM 15,960 per quality-adjusted life-year gained.The results of the decision-analytic model support the use of fentanyl-TTS as a favorable cost-effective option for the treatment of moderate to severe nonmalignant pain.

Putting your money where your mouth is: willingness to pay for dental gel

OBJECTIVES

To measure preferences and willingness to pay (WTP) for a novel anaesthetic (dental gel) versus existing anaesthetic options for periodontal maintenance visits.

DESIGN

The study was conducted by developing and administering a survey, composed of a modified decision aid and a WTP instrument. The decision aid provided clinical information in layman's terms. Patients stated their anaesthetic preference; WTP elicited the hypothetical amount of money a subject would pay to have dental gel available for maintenance cleaning, should they require anaesthetic.

PATIENTS

Periodontal recall patients (n = 97; 'recall') and participants from the general population (n = 196; 'general') from southwestern Ontario, Canada.

RESULTS

The overwhelming majority of participants chose dental gel over injectable local anaesthetic or no anaesthetic as their first anaesthetic preference (general: 81.0%; recall: 82.5%). The median WTP for dental gel was 20.00 Canadian dollars (dollars Can) per visit for the general population and dollars Can10.00 for the recall population (1999 values). The majority of participants were willing to pay an insurance premium for dental gel, even if they did not personally prefer dental gel (general: 72.4%; recall: 73.2%). The median monthly premium to have dental gel available for any plan beneficiary requiring scaling and root planing (SRP) during maintenance was dollars Can2.00 per month for both groups.

CONCLUSIONS

In this population, an alternative to traditional injectable local anaesthetic (i.e. dental gel) was overwhelmingly preferred by both general population participants and recall patients for maintenance cleaning procedures. Most participants were willing to pay to have dental gel available, either for themselves or for others.

Use of an interactive tool to assess patients' willingness-to-pay

Assessment of willingness to pay (WTP) has become an important issue in health care technology assessment and in providing insight into the risks and benefits of treatment options. We have accordingly explored the use of an interactive method for assessment of WTP. To illustrate our methodology, we describe the development and testing of an interactive tool to administer a WTP survey in a dental setting. The tool was developed to measure patient preference and strength of preference for three dental anesthetic options in a research setting. It delivered written and verbal formats simultaneously, including information about the risks and benefits of treatment options, insurance, and user-based WTP scenarios and questions on previous dental experience. Clinical information was presented using a modified decision aid. Subjects could request additional clinical information and review this information throughout the survey. Information and question algorithms were individualized, depending on the subject's reported clinical status and previous responses. Initial pretesting resulted in substantial modifications to the initial tool: shortening the clinical information (by making more of it optional reading) and personalizing the text to more fully engage the user. In terms of results 196 general population subjects were recruited using random-digit dialing in southwestern Ontario, Canada. Comprehension was tested to ensure the instrument clearly conveyed the clinical information; the average score was 97%. Subjects rated the instrument as easy/very easy to use (99%), interesting/very interesting (91%), and neither long nor short (72.4%). Most subjects were comfortable/very comfortable with a computer (84%). Indirect evaluation revealed most subjects completed the survey in the expected time (30 min). Additional information was requested by 50% of subjects, an average of 2.9 times each. Most subjects wanted this type of information available in the provider's office for use in clinical decision making (92%). Despite extensive pretesting, three "bugs" remained undiscovered until live use. We have demonstrated that the detailed information, complex algorithms, and cognitively challenging questions involved in a WTP survey can be successfully administered using a tailor-made, patient-based, interactive computer tool. Key lessons regarding the use of such tools include allowing the user to set the pace of information flow and tailor the content, engaging the user by personalizing the textual information, inclusion of tests of comprehension and offering opportunities for correction, and pretesting by fully mimicking the live environment.

The relative sensitivity of willingness-to-pay and time-trade-off to changes in health status: an empirical investigation

This paper directly compares the relative sensitivity of time-trade-off (TTO) and willingness-to-pay (WTP) values obtained for various levels of change in health status. This was achieved by administering a TTO and WTP survey to a population of 50 subjects, assessing their valuation of various degrees of change in health status. It was found that, overall, WTP is more sensitive than TTO in distinguishing between different dimensions of health at the same nominal level of health status (only four WTP values not significantly different, compared with eight TTO values). In addition, WTP was also more sensitive to differences in quality of life between different levels of health within each dimension (all values significantly different from each other, with TTO yielding three insignificant relationships). These results tentatively suggest, therefore, that WTP seems to be a more sensitive measure of change in health status than TTO.

The reliability and internal consistency of an Internet-capable computer program for measuring utilities

OBJECTIVE

The purpose of this study was to assess the reliability and internal consistency of measurements of utilities performed with a computer program (iMPACT2) designed for Internet surveys and Internet patient decision-support systems.

METHODS

We implemented the Internet Multimedia Preference Assessor Construction Tool, version 2 (iMPACT2) program using the combination of a web server, HTML files, and a web-accessible database. The program randomized subjects, screened their responses for missing data and failures of internal consistency, assisted patients with resolving certain inconsistencies, and, upon a subject's completion of the protocol, provided a report of results to the research assistant administering the program. To validate the iMPACT2 program, we recruited 60 healthy community volunteers and elicited preferences in a research-lab setting using a visual analog scale (VAS) and the standard gamble (SG) for subject's current health and three hypothetical states. For purposes of comparison, we also administered a Short Form-12 (SF-12) health-assessment questionnaire. Subjects used the computer software on two occasions separated by 2-4 weeks of time.

RESULTS

Visual analog scale and standard gamble ratings for subjects' current health were reliable (intraclass correlation coefficient (ICC) of 0.82 and 0.84 (two outliers excluded -0.60 without exclusions), respectively) were comparable with the reliability of the Physical and Mental Component scales of the SF-12 (ICCs of 0.84 and 0.75, respectively). Subjects could easily discriminate between hypothetical states (D scores 0.74 for SG and 0.90 for VAS), and 94% had a completely internally consistent ordering of preference ratings for states.

CONCLUSIONS

iMPACT2 produces measurements of standard gamble utilities that are reliable and have a high degree of internal consistency. Procedures for assessment of utilities developed for desktop computer programs can be translated to software designed for the Internet, facilitating the use of utilities and endpoints in clinical trials and development of web-based decision-support applications for patients. However, further testing, including direct comparisons with traditional interviewer administered utility elicitation protocols, is needed.

The epidemiology of herpes zoster and potential cost-effectiveness of vaccination in England and Wales

The epidemiology of herpes zoster and post-herpetic neuralgia (PHN) was quantified from a variety of data sources and the potential cost-effectiveness of vaccination assessed. The annual incidence and severity of zoster increases sharply with age, as measured by physician consultation and hospitalisation rates, average length of stay, average proportion of cases developing PHN and the age-specific case-fatality ratio. Combining these data with information on health related quality of life results in an estimated loss of 20000 quality adjusted life years (QALYs) annually in England and Wales from herpes zoster (17400 due to PHN). The current cost of treating herpes zoster associated disease is estimated to be 47.6m pounds annually. Since both the health and economic burden are high, vaccination of the elderly is expected to be cost-effective under most scenarios, the attractiveness of immunisation increasing with age due to the increased burden of disease in the very elderly.

Critical issues in the economic evaluation of interventions against communicable diseases

Economic appraisal seeks to provide policy-makers with guidance about how scarce resources can be used to derive the greatest possible social benefit. Its use in the health sector has increased dramatically over the last decade although much of it has been focused on the problems of the more developed countries. The relatively sparse literature on communicable diseases has been dominated by interventions related to HIV/AIDS, hepatitis, malaria and tropical diseases. Reviews of this literature from the perspective of specific conditions such as Hepatitis B are already available, and recently the entire literature has been evaluated against the technical criteria for economic evaluations published in standard textbooks. Accordingly, this paper focuses on issues which would make economic appraisal more useful to policy-makers than it currently is. Given that few countries have the resources to undertake all the necessary analysis in their own settings, it is important that studies in one setting are undertaken in a way that allow generalisability to similar settings. Some of the most important challenges this poses for cost-effectiveness analysis (CEA) are identified. Firstly, incremental analysis is appropriate to local decision making when policy-makers are constrained to keep the current interventions and can consider only marginal improvements. However, it does not allow re-evaluation of existing interventions and is not transferable across settings. A version of Generalised CEA is proposed as an alternative. Secondly, data on costs and effectiveness are often not presented appropriately. The challenge for effectiveness is to adjust the evidence from efficacy studies to allow for different patient or population groups, and local variations in adherence, coverage, and infrastructure. For costs, it is important for studies to report the physical resources used in an intervention as well as unit prices. Thirdly, some long-term effects are still not well incorporated into CEA, especially those affecting child development and drug resistance. These questions are technically challenging and require more concerted efforts over the next few years. Finally, it is important for analysts to provide decision-makers with estimates of the resources that would be required to implement interventions claimed to be cost-effective. These improvements would better enable the evidence from economic analyses to enter the policy debate and be weighed against the other goals and objectives of the health system when allocating scarce resources.

Economic evaluation of the fentanyl transdermal system for the treatment of chronic moderate to severe pain

The fentanyl transdermal system (Duragesic) is an opioid analgesic indicated for the management of chronic moderate to severe pain. The purpose of this analysis is to estimate its economic value compared to two long-acting oral opioids. A cost-utility analysis was performed using a three-phased decision analytic model. The transdermal system had the highest expected cost during the first year of therapy ($2,491), moderately higher than the cost of a year of therapy with controlled-release morphine ($2,037) or controlled-release oxycodone ($2,307). The system also had the highest expected number of quality-adjusted life-days (QALDs) (244 compared to 236 for morphine and 231 for oxycodone), despite conservative assumptions. The fentanyl transdermal system achieved incremental cost-utility ratios of $20,709 (vs. morphine) and $5,273 (vs. oxycodone) per quality-adjusted life year (QALY) gained. In a conservative modeled analysis, the fentanyl transdermal system led to increased QALDs at a nominal increased cost. In the absence of head-to-head clinical trials, models help clarify cost and outcome trade-offs and provide a consistent theoretical framework for use by individual decisionmakers.

Are health states "timeless"? The case of the standard gamble method

The standard gamble method, as currently recommended for use in health care program evaluation, provides an individual's preference score or "utility weight" for living in a given health state for the rest of the individual's life. Many researchers interpret this value as a time-independent or "timeless" one and order health states on a scale of zero (death) to one (full health), regardless of the time spent in the health state. This article examines whether preference scores for a severe pain health state are "timeless," or in other words whether the utility independence assumption is satisfied. Our study results suggest that for the majority of respondents, the preference scores are not independent of time.

Use of contingent valuation to place a monetary value on pharmacy services: an overview and review of the literature

An important goal for the pharmacy profession is to quantify the economic value of pharmacy services. The contingent valuation (CV), or willingness-to-pay method, offers one approach to valuing the benefits of pharmacy services. The potential advantage CV offers is that it reflects, in a single monetary amount, the entire range of attributes (both benefits and "nonbenefits") offered by the good or service being valued. This paper provides a brief overview of the CV method and reviews 10 published studies that used a willingness-to-pay question to place a monetary value on pharmacy services. Suggestions for other researchers wishing to use this method are provided.