Valuing avoided morbidity using meta-regression analysis: what can health status measures and QALYs tell us about WTP?

Willingness to pay for a quality-adjusted life year: a systematic review with meta-regression

The use of a threshold for cost-utility studies is of major importance to health authorities for making the best allocation decisions for limited resources. Regarding the increasing number of studies worldwide that seek to establish a value for a quality-adjusted life year (QALY), it is necessary to review these studies to provide a global insight into the literature. A systematic review on willingness to pay (WTP) studies focusing on QALY was conducted in eight databases up to June 26, 2020. From a total of 9991 entries, 39 studies were selected, and 511 observations were extracted for the meta-analysis using the ordinary least squares method. The results showed a predicted mean empirical value of $52,619.39 (95% CI 49,952.59; 55,286.19) per QALY in US dollars for 2018. A 1% increase in income led to an increase of 0.6% in the WTP value, while a 1-year increase in respondent age led to a decrease of 3.3% in the WTP value. Sex, education level and employment status had significant effects on WTP. Compared to face-to-face interviews, surveys conducted by the internet or telephone were more likely to have a significantly higher value of WTP per QALY, while out-of-pocket payment tended to lower the value. The prediction made for the province of Quebec, Canada, provided a QALY value of approximately USD $98,450 (CAD $127,985), which is about 2.3 times its gross domestic product (GDP) per capita in 2018. This study is consistent with the extant literature and will be useful for countries that do not yet have a preference-based survey for the value of a QALY.

Willingness to pay vs lottery equivalent to value the impact of alcohol misuse on quality of life

OBJECTIVES

To estimate the impact of alcohol disorders using lottery equivalent (LE) and willingness to pay (WTP) methods and compute the WTP for a QALY (WTP-Q) derived from these values.

METHODS

Two samples of 300 people valued nine states of alcohol misuse. LE and WTP were used in sample 1 and 2, respectively. The ability to discriminate between methods was tested. Regression models were performed to estimate the preference weights of dimensions. Several values of WTP-Q were obtained by combining the estimated values from both samples.

RESULTS

LE and WTP produce the same ranking of states but LE is more sensitive. The estimated impact of the nine states ranges between 0.91 and 0.22 QALYs, and the WTP for avoiding them ranges between €10,444 and €4132. WTP-Q varies between €11,473 and €19,092 when the mean values of the states are used. The WTP-Q tends to decrease with the severity.

CONCLUSIONS

Although LE and WTP provide values for cost-utility and cost-benefit analyses, respectively, LE seems to be preferable for measuring the impact of alcohol disorders. As the lower sensitivity of WTP seems to explain a WTP-Q decrease with severity, more research is needed before recommending the use of different WTP-Q values.

A systematic review and meta-regression of studies eliciting willingness-to-pay per quality-adjusted life year in the general population

OBJECTIVES

From the demand-side perspective, the monetary value of one additional quality-adjusted life year (QALY) is estimated as willingness-to-pay per QALY (WTPQ). This study aims to summarize the methods and contexts of elicitation of willingness-to-pay per quality-adjusted life year (WTPQ) in the general population and to investigate the heterogeneity of WTPQ estimates.

METHODS

Meta-regression analysis was conducted using Comprehensive Meta-Analysis Software. Sensitivity analyses were undertaken by replacing the lowest and highest 5% and 2.5% of WTPQ by percentiles.

RESULTS

33 studies with 102 WTPQ estimates were included. The overall mean and median WTPQ estimates are $1,280,002 and $44,072, respectively. The meta-regressions demonstrated that types of health gain (quality of life or life length) and certainty of health outcomes are statistically significant factors. Furthermore, compared with online interviews, face-to-face interviews tend to yield lower WTPQ. Moreover, the declining trend of QALY gains and positive effect with statistical significance of the sample age were also noticed.

CONCLUSION

For valid and representative values of WTPQ, future researchers should therefore take into consideration various scenarios and investigate both health gain with certainty and uncertainty, health gain from both life length and quality of life, and different size of QALY gains.

Theoretical bounds on the value of improved health

Policies that improve health and longevity are often valued by combining expected gains in quality-adjusted life years (QALYs) with a constant willingness-to-pay (WTP) per QALY. This constant is derived by dividing value per statistical life (VSL) estimates by expected future QALYs. We explore the theoretical validity of this practice by studying the properties of WTP for improved health and longevity in a framework that makes minimal assumptions about the shape of an agent's utility function. We find that dividing VSL by expected QALYs results in an upper bound on the WTP for a marginal improvement in the quality of life, as measured by gains in health status or longevity. Calibration results suggest that analysts using this approach to monetize health benefits overestimate the value of a program or policy by a factor of two on average. We also derive a lower bound on the WTP for improved health and longevity that permits a novel empirical test for the descriptive validity of the QALY model. Our calibrations suggest that this lower bound is on average 20% smaller than the actual WTP.

Differential discounting in the economic evaluation of healthcare programs

Background

The question of appropriate discount rates in health economic evaluations has been a point of continuous scientific debate. Today, it is widely accepted that, under certain conditions regarding the social objective of the healthcare decision maker and the fixity of the budget for healthcare, a lower discount rate for health gains than for costs is justified if the consumption value of health is increasing over time. To date, however, there is neither empirical evidence nor a strong theoretical a priori supporting this assumption. Given this lack of evidence, we offer an additional approach to check the appropriateness of differential discounting.

Methods

Our approach is based on a two-goods extension of Ramsey's optimal growth model which allows accounting for changing relative values of goods explicitly. Assuming a constant elasticity of substitution (CES) utility function, the growth rate of the consumption value of health depends on three variables: the growth rate of consumption, the growth rate of health, and the income elasticity of the willingness to pay for health. Based on a review of the empirical literature on the monetary value of health, we apply the approach to obtain an empirical value of the growth rate of the consumption value of health in Germany.

Results

The empirical literature suggests that the income elasticity of the willingness to pay for health is probably not larger but rather smaller than 1 and probably not smaller but rather larger than 0.2. Combining this finding with reasonable values of the annual growth rates in consumption (1.5-1.6%) and health (0.1%) suggests, for Germany, an annual growth rate of the consumption value of health between 0.3 and 1.5%.

Conclusion

In the light of a two-goods extension of Ramsey's optimal growth model, the available empirical evidence makes the case for a growing consumption value of health. Therefore, the current German practice of applying the same discount rate to costs and health gains introduces a systematic bias against healthcare technologies with upfront costs and long-term health effects. Differential discounting with a lower rate for health effects appears to be a more appropriate discounting model.

Exposure to outdoor air pollution and its human health outcomes: A scoping review

Despite considerable air pollution prevention and control measures that have been put into practice in recent years, outdoor air pollution remains one of the most important risk factors for health outcomes. To identify the potential research gaps, we conducted a scoping review focused on health outcomes affected by outdoor air pollution across the broad research area. Of the 5759 potentially relevant studies, 799 were included in the final analysis. The included studies showed an increasing publication trend from 1992 to 2008, and most of the studies were conducted in Asia, Europe, and North America. Among the eight categorized health outcomes, asthma (category: respiratory diseases) and mortality (category: health records) were the most common ones. Adverse health outcomes involving respiratory diseases among children accounted for the largest group. Out of the total included studies, 95.2% reported at least one statistically positive result, and only 0.4% showed ambiguous results. Based on our study, we suggest that the time frame of the included studies, their disease definitions, and the measurement of personal exposure to outdoor air pollution should be taken into consideration in any future research. The main limitation of this study is its potential language bias, since only English publications were included. In conclusion, this scoping review provides researchers and policy decision makers with evidence taken from multiple disciplines to show the increasing prevalence of outdoor air pollution and its adverse effects on health outcomes.

The welfare value of FDA's mercury-in-fish advisory: a dynamic reanalysis

Assessing the welfare impact of consumer health advisories is a thorny task. Recently, Shimshack and Ward (2010) studied how U.S. households responded to FDA's 2001 mercury-in-fish advisory. They found that the average at-risk household reduced fish consumption by 21%, resulting in a 17%-reduction in mercury exposure at the cost of a 21%-reduction in cardioprotective omega-3 fatty acids. Based on a static assessment of the health costs and benefits Shimshack and Ward concluded that the advisory policy resulted in an overall consumer welfare loss. In this note, we propose a dynamic assessment that links the long-term cardiovascular health effects of the advisory to life-cycle consumption. We find that under reasonable assumptions the welfare loss might be much larger than suggested. Our analysis highlights the importance of accounting for dynamic effects when evaluating persistent changes in exposure to environmental health risks.

The value of a QALY: individual willingness to pay for health gains under risk

BACKGROUND

There is an increased interest in the monetary value of a quality-adjusted life-year (QALY). Past studies commonly derived willingness to pay (WTP) for certain future QALY gains. However, obtaining valid WTP per QALY estimates proved to be difficult.

OBJECTIVE

We conducted a contingent valuation study and estimated the individual WTP per QALY under risk. We demonstrate the impact of probability weighting on WTP per QALY estimates in the Netherlands.

RESULTS

Our estimates of the value of a QALY are in the range of €80,000-110,000 when the weighting correction was applied, and €250,500 without correction. The validity of these estimates, applying probability weighting, appears to be good.

CONCLUSIONS

Given the reasonable support for their validity and practical meaningfulness, the estimates derived while correcting for probability weighting may provide valuable input for the debate on the consumption value of health. While decision makers should not apply these estimates without further consideration, since strictly individual valuations may not carry all relevant information and values for societal decision-making, the current estimates may provide a good and informed basis for further discussion and study of this important topic.

Willingness to pay for a QALY: past, present and future

This paper is focused on establishing why a willingness-to-pay per quality-adjusted life-year value is needed and how such a value can be used in healthcare decision-making. Studies that have estimated willingness-to-pay per quality-adjusted life-year values from stated preference data are reviewed and categorized into three groups. These studies are then compared within and between groups highlighting the limitations of existing studies and their suitability for use in policy-making. The future of such work will be discussed, noting key issues for consideration and debate.

GET MORE, PAY MORE? An elaborate test of construct validity of willingness to pay per QALY estimates obtained through contingent valuation

Estimates of WTP per QALY can be taken as an indication of the monetary value of health gains, which may carry information regarding the appropriate height of the cost-effectiveness threshold. Given the far-reaching consequences choosing a particular threshold, and thus the potential relevance of WTP per QALY estimates, it is important to address the validity of these estimates. This study addresses this issue. Our findings offer little support to the validity of WTP per QALY estimates obtained in this study. Implications for general WTP per QALY estimates and further research are discussed.

The monetary value of a life year: evidence from a qualitative study of treatment costs

A small number of studies have provided suggestive evidence that the general public rejects the idea of giving higher priority to low-cost patients, in the context of a limited budget, in order to maximise health benefits. The study reported here used semi-structured group discussions to investigate the normative bases of such views among the Australian public. Discussion groups help participants reflect critically upon their own reasoning processes and go some way towards revealing underlying values rather than unreflective preferences. As a part of the exercise, participants were asked to allocate a hospital budget. After discussion and deliberation only three out of 41 chose to allocate all of the money to the low-cost patients. Reasons were not based on conceptual confusion or lack of insight into the implications of the different strategies, but rather on views about fairness, including the importance of giving all groups a 'chance' of being treated and of not removing 'hope' from high-cost patients. The results suggest that as costs rise people are willing to pay more than the minimum cost of a quality-adjusted life year for equity reasons, indicating that caution must be exercised in estimating a single monetary value for a QALY.

Willingness to pay for a quality-adjusted life-year: the individual perspective

OBJECTIVE

The aim of this study was to elicit the individual willingness to pay (WTP) for a quality-adjusted life-year (QALY).

METHODS

In a Web-based questionnaire containing contingent valuation exercises, respondents valued health changes in five scenarios. In each scenario, the respondents first valued two health states on a visual analog scale (VAS) and expressed their WTP for avoiding a decline in health from the better health state to the worse, using a payment scale followed by a bounded open contingent valuation question.

ANALYSIS

WTP per QALY was calculated for QALY gains calculated using VAS valuations, as well as the Dutch EQ-5D tariffs, the two steps in the WTP estimations and each scenario. Heterogeneity in WTP per QALY ratios was examined from the perspective of: 1) household income; and 2) the level of certainty in WTP indicated by respondents. Theoretical validity was analyzed using clustered multivariate regressions.

RESULTS

A total of 1091 respondents, representative of the Dutch population, participated in the survey. Mean WTP per QALY was € 12,900 based on VAS valuations, and € 24,500 based on the Dutch EuroQoL tariffs. WTP per QALY was strongly associated with income, varying from € 5000 in the lowest to € 75,400 in the highest income group. Respondents indicating higher certainty exhibited marginally higher WTP. Regression analyses confirmed expected relations between WTP per QALY, income, and other personal characteristics.

CONCLUSION

  Individual WTP per QALY values elicited in this study are similar to those found in comparable studies. The use of individual valuations in social decision-making deserves attention, however.

Contingent valuation: what needs to be done?

Contingent valuation (CV) has been argued to have theoretical advantages over other approaches for benefit valuation used by health economists. Yet, in reality, the technique appears not to have realised these advantages when applied to health-care issues, such that its influence in decision-making at national levels has been non-existent within the health sector. This is not a result of a lack of methodological work in the area, which has continued to flourish. Rather, it is a result of such activities being undertaken in a rather uncoordinated and unsystematic fashion, leading CV to be akin to a 'ship without a sail'. This paper utilises a systematic review of the CV literature in health to illustrate some important points concerning the conduct of CV studies, before providing a comment on what the remaining policy and research priorities are for the technique, and proposing a guideline for such studies. It is hoped that this will initiate some wider and rigorous debate on the future of the CV technique in order to make it seaworthy, give it direction and provide the right momentum.

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.

Willingness to pay for a QALY based on community member and patient preferences for temporary health states associated with herpes zoster

BACKGROUND AND OBJECTIVES

A clear sense of what society is willing to pay for a QALY could enhance the usefulness of cost-effectiveness analysis as a field. Scant information exists on willingness to pay (WTP) for a QALY based on direct elicitation of preferences from community members or patients. We had the opportunity to evaluate WTP per QALY using data from a survey on temporary health outcomes related to herpes zoster. Our aims were to (i) describe how much community members are willing to pay to save a QALY based on scenarios describing temporary health states; (ii) evaluate how WTP per QALY varies based on experience with the disease being described and with demographic variables; and (iii) evaluate how the duration and intensity of pain in a scenario influences WTP per QALY.

METHODS

Community members drawn from a nationally representative survey research panel (n = 478) completed an Internet-based survey using time trade-off (TTO) and WTP questions to value a series of scenarios that described herpes zoster cases of varying pain intensity (on a scale of 0-10) and duration (30 days to 1 year). Patients with shingles (n = 354) or postherpetic neuralgia (PHN; n = 120) [defined as having symptoms for 90 days or more] from two large healthcare systems completed telephone interviews with similar questions. Mean and median WTP per QALY values were calculated by dividing the WTP amount by the discounted time traded for each scenario. Responses with a WTP value of more than zero and a TTO value of zero (which would have resulted in an undefined value) were excluded. TTO values were discounted by 3% per year. WTP per QALY means were calculated after trimming the top and bottom 2.5% of responses. Multivariate analyses were conducted using generalized linear mixed models that assumed a negative binomial distribution.

RESULTS

Among all respondents, the WTP per QALY ranged from a median of $US7000 to $US11,000 and a trimmed mean of $US26 000 to $US45,000 (year 2005 values), depending on the scenario described. WTP per QALY values varied significantly with respondent characteristics, as well as among respondents with similar characteristics. In multivariate analyses, the mean WTP per QALY was higher among respondents who were younger, male or had higher educational or income levels. After adjusting for these demographic variables, patients who had experienced shingles gave responses with the highest WTP per QALY values. Patients who had experienced PHN gave the lowest values, and community members gave values intermediate to the shingles and PHN groups. In multivariate models that evaluated the effects of pain and duration of the hypothetical zoster scenario, lower duration was associated with higher WTP per QALY. This effect appeared to be due to people increasing the amounts of time they would be willing to trade as duration increased, without proportional increases in the amounts of money they would be willing to pay.

CONCLUSIONS

Community members and patients gave mean WTP per QALY values that varied significantly based on age, sex, socioeconomic status, experience with shingles and duration of the health state evaluated. The variability in WTP per QALY suggests that it may be difficult to define a unitary threshold of dollars per QALY for policy making based on cost-effectiveness analyses.

Ancillary human health benefits of improved air quality resulting from climate change mitigation

BACKGROUND

Greenhouse gas (GHG) mitigation policies can provide ancillary benefits in terms of short-term improvements in air quality and associated health benefits. Several studies have analyzed the ancillary impacts of GHG policies for a variety of locations, pollutants, and policies. In this paper we review the existing evidence on ancillary health benefits relating to air pollution from various GHG strategies and provide a framework for such analysis.

METHODS

We evaluate techniques used in different stages of such research for estimation of: (1) changes in air pollutant concentrations; (2) avoided adverse health endpoints; and (3) economic valuation of health consequences. The limitations and merits of various methods are examined. Finally, we conclude with recommendations for ancillary benefits analysis and related research gaps in the relevant disciplines.

RESULTS

We found that to date most assessments have focused their analysis more heavily on one aspect of the framework (e.g., economic analysis). While a wide range of methods was applied to various policies and regions, results from multiple studies provide strong evidence that the short-term public health and economic benefits of ancillary benefits related to GHG mitigation strategies are substantial. Further, results of these analyses are likely to be underestimates because there are a number of important unquantified health and economic endpoints.

CONCLUSION

Remaining challenges include integrating the understanding of the relative toxicity of particulate matter by components or sources, developing better estimates of public health and environmental impacts on selected sub-populations, and devising new methods for evaluating heretofore unquantified and non-monetized benefits.

Methods for the meta-analysis of willingness-to-pay data: an overview

Given the policy relevance and growing volume of research measuring individuals' willingness to pay (WTP) for health-related goods and services, meta-analysis provides a potentially rich set of tools for answering key questions about this research area. In particular, when taken as a whole, what does the existing empirical literature tell us about health preferences, the effectiveness of health policies, and the demand for health-related goods and services? Although the application of meta-analysis techniques to health-related WTP data is fundamentally similar to other meta-analysis applications, it nonetheless presents a number of specific challenges. The purpose of this article is to describe some of the main features that distinguish WTP research and to discuss ways in which meta-analysis methods must be tailored to meet these challenges. One of the most notable features of this research area is its heterogeneity in terms of research methods, reporting practices and publication outlets. This article discusses the implications of this diversity for the methods used at various stages of meta-analysis, including problem formulation, data collection, data evaluation and abstraction, data preparation and data analysis. One central implication is a strong reliance on meta-regression and panel data approaches. Another key feature is the frequent objective of providing benefit estimates for economic evaluation. The implication for meta-analysis is that it is a powerful tool not only for synthesizing results and testing hypotheses, but also for predicting WTP and generating benefit estimates for a variety of scenarios. This article discusses what this role implies for how meta-analysis is conducted and how the results are reported.