Correcting Biases in Standard Gamble and Time Tradeoff Utilities

Patients, doctors and risk attitudes

A lively topic of debate in decision theory over recent years concerns our understanding of the different risk attitudes exhibited by decision makers. There is ample evidence that risk-averse and risk-seeking behaviours are widespread, and a growing consensus that such behaviour is rationally permissible. In the context of clinical medicine, this matter is complicated by the fact that healthcare professionals must often make choices for the benefit of their patients, but the norms of rational choice are conventionally grounded in a decision maker's own desires, beliefs and actions. The presence of both doctor and patient raises the question of whose risk attitude matters for the choice at hand and what to do when these diverge. Must doctors make risky choices when treating risk-seeking patients? Ought they to be risk averse in general when choosing on behalf of others? In this paper, I will argue that healthcare professionals ought to adopt a deferential approach, whereby it is the risk attitude of the patient that matters in medical decision making. I will show how familiar arguments for widely held anti-paternalistic views about medicine can be straightforwardly extended to include not only patients' evaluations of possible health states, but also their attitudes to risk. However, I will also show that this deferential view needs further refinement: patients' higher-order attitudes towards their risk attitudes must be considered in order to avoid some counterexamples and to accommodate different views about what sort of attitudes risk attitudes actually are.

Valuing indigenous quality of life: A review of preference-based quality of life instruments and elicitation techniques with global older indigenous populations

Indigenous perspectives of quality of life (QoL) are different to that of non-Indigenous populations. Determining how to identify and value what is important to QoL for people from diverse cultural backgrounds is crucial for assessing effective outcomes for quality assessment and health economic evaluation to guide evidence-based decision making. This is particularly important for older Indigenous people who have complex care and support needs within health and aged-care systems. This scoping review aims to assess the existing literature in this field by firstly identifying preference based instruments that have been applied with older Indigenous peoples and secondly, exploring the extent to which existing preference based instruments applied with older Indigenous peoples encompass older Indigenous peoples QoL perspectives in their design and application. The inclusion criteria for the review were studies using preference based QoL instruments with an Indigenous population where the cohort was aged 50 years or over. This resulted in the critical analysis of 12 studies. The review identified that preference based QoL instruments have rarely been applied to date with older Indigenous populations with most instruments found to be designed for non-Indigenous adults. Typically, instruments have not incorporated Indigenous worldviews of QoL into either the content of the descriptive system or the elicitation techniques and corresponding value sets generated. To encapsulate Indigenous cultural perspectives accurately in economic evaluation, further research is required as to how QoL domains in preference based instruments for Indigenous peoples can be reflective of Indigenous perspectives. It is imperative that the QoL preferences of older Indigenous peoples are adequately captured within preference based QoL instruments applied with this population.

How Much Better is Faster? Value Adjustments for Health-Improvement Sequences

While the quality-adjusted life-year construct has advantages of simplicity and consistency, simplicity requires strong assumptions. In particular, standard assumptions result in health-state utility functions that are unrealistically linear and separable in risk and duration. Consequently, sequencing of a series of health improvements has no effect on the total value of the sequence because each increment is assessed independently of previous increments. Utility functions in nearly all other areas of applied economics are assumed to be nonlinear with diminishing marginal utility so it matters where an improvement occurs in a sequence. We construct a conceptual framework that that demonstrates how diminishing marginal utility for health improvements could affect preferences for different sequence patterns. Using this framework, we derive conditions for which the sum of conventional health-state utilities understates, overstates, or approximates the sequence-sensitive value of health improvements. These patterns suggest the direction and magnitude of possible adjustments to conventional value calculations. We provide numerical examples and identify recent studies whose results are consistent with the conceptual model.

An experimental investigation of social risk preferences for health

In this paper, we use the risk apportionment technique of Eeckhoudt, Rey and Schlesinger (2007) to study higher order risk preferences for others' health as well as ex-ante and ex-post inequality preferences for social risky distributions, and their interaction. In an experiment on a sample of university students acting as impartial spectators, we observe risk aversion towards social health losses and a dislike of ex-ante inequality. In addition, evidence for ex-post inequality seeking is much weaker than evidence for ex-ante inequality aversion. Because ex-ante inequality aversion is unrelated to risk aversion, we conclude that simple forms of utilitarianism are not relevant for individual judgment of social risk over health. Last, our investigation of precautionary distribution, which would occur when one particular group in the society suffers from background health risk, shows substantial polarization of preferences.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11238-023-09928-w.

Correcting for discounting and loss aversion in composite time trade-off

Time trade-off utilities have been suggested to be biased upwards. This bias is a result of the method being applied assuming linear utility of life duration, which is violated when individuals discount future life years or are loss averse for health. Applying a "corrective approach", that is, measuring individuals' discount function and loss aversion and correcting time trade-off utilities for these individual characteristics, may reduce this bias in utilities. Earlier work has developed this approach for time trade-off in a student sample. In this study, the corrective approach was extended to composite time trade-off (cTTO) methodology, which enabled correcting utilities for health states worse than dead. In digital interviews a sample of 150 members of the general public completed cTTO tasks for six health states, and afterward they completed measurements of loss aversion and discounting. cTTO utilities were corrected using these measurements under multiple specifications. Respondents were also asked to reflect on and adjust their cTTO utilities directly. Our results show considerable loss aversion and both positive and negative discounting were prevalent. As predicted, correction generally resulted in lower utilities. This was in accordance with the direction of adjustments made by respondents themselves.

Defining Utility Values for Chorea Health States in Patients with Huntington's Disease

Introduction

Chorea is characterized by sudden, involuntary movements that interfere with quality of life (QOL). Utility values measure preferences for different health states and reflect societal perceived disease severity. To date, no studies have reported utility values specifically for Huntington’s disease (HD) chorea. We estimated impact on QOL of HD chorea severity using utility values from the general population.

Methods

Participants were enrolled using computer-assisted telephone interviews. Participants read vignettes describing four health states for varying levels of chorea severity, with the same underlying HD severity. Time trade-off (TTO) methods were used to estimate utility values, which range from −1 (worse than death) to +1 (perfect health) and represent the number of years in an imperfect health state an individual is willing to give up to live in full health. TTO utilities were augmented with visual analog scale (VAS) participant responses. The primary outcome was HD chorea utility estimated by TTO.

Results

Mean ± SD TTO-derived utility values were 0.07 ± 0.52, 0.26 ± 0.50, 0.48 ± 0.47, and 0.64 ± 0.41 for severe, moderate/severe, moderate/mild, and mild chorea severity, respectively. Differences between each health state and its adjacent less severe health state were statistically significant (all P < 0.0001). Respondents were willing to give up 3.6, 5.2, 7.4, and 9.3 years during a 10-year life span to avoid living with mild, mild/moderate, moderate/severe, and severe chorea, respectively. VAS and TTO results were consistent.

Conclusions

Significant decreases in utility values were seen as HD chorea severity increased. These data can be leveraged for cost-effectiveness modeling to better understand the value of treatments for chorea.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12325-022-02046-z.

Defining utility values for patients with tardive dyskinesia

OBJECTIVE

To measure health state preferences and estimate utility values for tardive dyskinesia (TD) from the perspective of the US general population, accounting for factors affecting quality of life (QOL).

METHODS

Participants from the general population were recruited and asked to watch and assess videos of professional actors simulating nine health states, including psychiatric disorders with/without TD and moderate-to-severe TD without any underlying disease. Time tradeoff (TTO) methods were used to elicit utility values, which ranged from -1 (worse than death) to +1 (perfect health) and represented individual preferences for avoiding specific health states associated with TD. Lower TTO utility values indicated individuals' willingness to give up more years of life to avoid living in each health state.

RESULTS

Based on TTO responses (n = 157), mean ± standard deviation utility for TD alone was 0.59 ± 0.38. Mean utilities for schizophrenia with negative symptoms (without TD: 0.43; with TD: 0.29) and positive symptoms (without TD: 0.44; with TD: 0.30) were generally lower than those for bipolar disorder (without TD: 0.59; with TD: 0.46) and major depressive disorder (without TD: 0.60; with TD: 0.44). According to utility decrements associated with TD (0.13-0.16), respondents were willing to give up 1.3 to 1.6 years during a 10-year lifespan to avoid living with TD.

CONCLUSIONS

Utility decrements for TD in this study were slightly larger than previously reported values, potentially due to incorporation of QOL and social consequences in TD health state descriptions. An important limitation of this analysis is that participants' willingness to trade future years of healthy life may not indicate actual willingness to accept the life decrement. These findings can be leveraged to improve cost-effectiveness analyses used to assess the value of treatments for TD.

Behavioral Theories That Have Influenced the Way Health State Preferences Are Elicited and Interpreted: A Bibliometric Mapping Analysis of the Time Trade-Off Method With VOSviewer Visualization

Aim

The aim of this paper is to develop an understanding of how behavioral theories have influenced the way preferences for health-related quality of life are elicited and interpreted. We focus on the Time Trade-off (TTO) method given it represents the quality-adjusted life-year (QALY) concept-that survival in less-than-full health can be deemed equivalent to a shorter survival in full health. To our knowledge this is the first review using a combination of systematic scoping review, bibliometrics and VOSviewer visualization to map the development of ideas in health economics.

Methods

A priori, we selected three behavioral theories to explore within our review, referred to here as Expected Utility Theory, Non-Expected Utility Theory and Probabilistic Choice Theory. A fourth topic, Order Effects, is defined broadly to encompass behavioral theories around timing/sequence of events. For the main search, Scopus was used to identify literature that had (a) elicited TTO values and/or (b) contributed to the way TTO values were elicited and interpreted, from inception to July 2021. Papers that focused on the latter category were given the label "behavioral" and underwent additional analyses. A two stage-screening was applied to assess eligibility. Co-citation, co-authorship and co-occurrence of keywords was used to chart the development of TTO over time.

Results

A total of 1,727 records were retrieved from Scopus and were supplemented by an additional 188 papers. There were 856 applied and 280 behavioral papers included in the final corpus, with the behavioral set split equally into four sets of 70 papers to chart the development of keywords over time: (1) 1972-1999; (2) 2000-2010, (3) 2010-2015 and (4) 2015-2021.

Discussion

The keyword analysis suggested that whilst some ideas transition quickly from economic theory to the TTO literature, such as the impact of Order Effects, others take longer to be assimilated, for example Non-Expected Utility models or failure of constant discounting. It is therefore important that researchers within health economics work more closely with those in mainstream economics and keep abreast of the wider economics and behavioral sciences to expedite the uptake of new and relevant ideas.

Cost-Utility Analysis of a Dolutegravir-Based Versus Low-Dose Efavirenz-Based Regimen for the Initial Treatment of HIV-Infected Patients in Cameroon (NAMSAL ANRS 12313 Trial)

OBJECTIVES

Evidence comparing the economic and patient values of the World Health Organization's preferred (dolutegravir 50 mg [DTG]-based) and alternative (low-dose [400 mg] efavirenz [EFV400]-based) first-line antiretroviral regimens is limited. We compared patient-reported outcomes (PROs), costs, and the cost-utility of DTG- versus EFV400-based regimens in treatment-naive HIV-1 adults in the randomised NAMSAL ANRS 12313 trial in Yaoundé, Cameroon.

METHODS

We used clinical data, PROs, and health resource use data collected in the trial's first 96 weeks (2016-2019). Quality-adjusted life-years (QALYs) were computed using utility scores obtained from the 12-item Short Form (SF-12) generic health scale. Other PROs included perceived symptoms, depression, anxiety, and stress. In the 96-week base-case analysis, we estimated the unadjusted and multivariate-adjusted (1) mean costs (in US$, 2016 values) and QALYs/patient, (2) incremental costs and QALYs/patient, and (3) net health benefit (NHB). Outcomes were extrapolated over 5 and 10 years. Uncertainty was assessed using the cost-effectiveness acceptability curve and scenario and cost-effective price threshold analyses.

RESULTS

In the base-case analysis, the NHB (95% confidence interval) for the DTG-based regimen relative to the EFV400-based regimen was 0.056 (- 0.037 to 0.153), corresponding to an 88% probability of DTG being cost-effective. A 10% decrease in this regimen's price (from $5.2 to $4.7/month) would increase its cost-effectiveness probability to 95%. When extrapolating outcomes over 5 and 10 years, the DTG-based regimen had a 100% probability of being cost-effective for a large range of cost-effectiveness thresholds.

CONCLUSIONS

At 2020 antiretroviral drug prices, a DTG-based first-line regimen should be preferred over an EFV400-based regimen in sub-Saharan Africa.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02777229.

Treatment selection for life-critical shared decision making under ranges of health-state utility scenarios

BACKGROUND

Selecting the best treatment for life-critical conditions via a shared decision making approach is a uniquely important challenge. Besides data from the healthcare physicians, other data that need to be considered are the personal values and perceptions of the patient. Usually, these data come in the form of health-state utility values. They are subjective and often times are elicited from the patient under emotional and stressful conditions. This paper examines an approach for selecting the best treatment under a life-critical shared decision making (SDM) framework.

METHODS

Health-state utility values are used in practice to quantify what is known as quality-adjusted life years (QALYs) and quality-adjusted life expectancy (QALE). The QALEs from different treatments are used to select the best treatment. This paper describes methods for determining QALEs under a range of scenarios defined by the way some key assumptions on the health-state utility values are satisfied. Approaches for comparing different treatments are described along with some counter-intuitive results. These approaches are based on some optimization formulations. The proposed approaches are demonstrated in terms of a real example taken from the literature.

RESULTS

Having results that are robust under a spectrum of different scenarios can provide more confidence that the most suitable treatment has been selected in a given case. On the other hand, having non-robust results can be useful information too as they may provide evidence that a more thorough assessment of the benefits and harms of the treatments may be needed to select a treatment with higher confidence. Finally, this study demonstrates that under certain mathematical conditions among the data it is possible to decide which treatment is better among two treatments without having to use health-state utility values.

CONCLUSION

The significance of this study is that it provides valuable and actionable insights for the important question of how health-state utilities can be used in treatment selection.

The Relative Impact of Urinary and Sexual Function vs Bother on Health Utility for Men With Prostate Cancer

Function and bother are related but distinct aspects of health-related quality of life. The objective of this study was to compare quantitatively the relative impacts of function and bother in urinary, sexual, and bowel outcomes on health utility as a reflection of health-related quality of life in men with prostate cancer. Our analysis included participants in the Cancer of the Prostate Strategic Urologic Research Endeavor utility supplementary study, with a final cohort of 1617 men. Linear regression on the patients’ function and bother summary scores (0-100) from the University of California, Los Angeles Prostate Cancer Index was performed to predict bias-corrected health utilities. Urinary and sexual bother were associated with each health utility, and their coefficients were 3.7 and 20.8 times greater, respectively, than those of the corresponding function. To our knowledge, our study provides the first quantitative and direct comparison of the impacts of function vs bother on health utility.

What is it going to be, TTO or SG? A direct test of the validity of health state valuation

Standard gamble (SG) typically yields higher health state valuations than time trade-off (TTO), which may be caused by biases affecting both methods. It has been suggested that TTO yields more accurate health state valuations, because TTO is subject to both upward and downward biases that may cancel out. Verifying this claim, however, would require a golden standard to test validity against. In this study, we attempted to provide a first direct test of the validity of health state valuation. A total of 119 students completed five TTO and SG tasks. Afterwards, their health state valuations elicited with TTO and SG were shown to them in an interactive graph. Respondents were asked to indicate which of the methods represented their valuation of a health state best. They could also adjust their valuation. Overall, we found that respondents indicated that TTO valuations better reflected health state valuations, a result that was more pronounced for more severe health states. When offered the opportunity, on average, respondents adjusted health state valuations downwards. These findings may have implications for future work on (bias correction in) health state valuations.

Creating a Health Utility Value for Birdshot Chorioretinopathy

PURPOSE

To create a health utility value for birdshot chorioretinopathy (BCR) using Time Trade-Off (TTO) and Standard Gamble (SG) utilities.

METHOD

Adult BCR patients completed TTO, SG, EQ-5D-5L, and NEI VFQ-25 questionnaires and underwent a detailed history and clinical examination.

RESULTS

A total of 28 BCR patients (9 M, 19 F; mean age 62 years, range 47-83) were included. There were 22 patients with a logMAR vision of 0.3 or better in both eyes. Mean TTO was 0.90 ± SD 0.18 (range 0.33-1.0) and mean SG was 0.94 ± SD 0.14 (range 0.5-1.0). TTO correlated with EQ-5D-5L index value (p = .024) and NEI VFQ-25 composite score (p = .015).

CONCLUSIONS

Of 28 patients with BCR, 11 would trade remaining life (mean 5.4 years), and 6 would take a risk of immediate death (mean 28% risk), in return for perfect vision in both eyes for the rest of their life.

Living up to expectations: Experimental tests of subjective life expectancy as reference point in time trade-off and standard gamble

Earlier work suggested that subjective life expectancy (SLE) functions as reference point in time trade-off (TTO), but has not tested or modelled this explicitly. In this paper we construct a model based on prospect theory to investigate these predictions more thoroughly. We report the first experimental test of reference-dependence with respect to SLE for TTO and extend this approach to standard gamble (SG). In two experiments, subjects' SLEs were used to construct different versions of 10-year TTO and SG tasks, with the gauge duration either described as occurring above or below life expectation. Our analyses suggest that both TTO and SG weights were affected by SLE as predicted by prospect theory with SLE as reference point. Subjects gave up fewer years in TTO and were less risk-tolerant in SG below SLE, implying that weights derived from these health state valuation methods for durations below SLE will be biased upwards.

QALYs without bias? Nonparametric correction of time trade-off and standard gamble weights based on prospect theory

Common health state valuation methodologies, such as standard gamble (SG) and time trade-off (TTO), typically produce different weights for identical health states. We attempt to alleviate these differences by correcting the confounding influences modeled in prospect theory: loss aversion and probability weighting. Furthermore, we correct for nonlinear utility of life duration. In contrast to earlier attempts at correcting TTO and SG weights, we measure and correct all these tenets simultaneously, using newly developed nonparametric methodology. These corrections were applied to three less-than-perfect health states, measured with TTO and SG. We found considerable loss aversion and probability weighting for both gains and losses in life years, and we observe concave utility for gains and convex utility for losses in life years. After correction, the initially significant differences in weights between TTO and SG disappeared for all health states. Our findings suggest new opportunities to account for bias in health state valuations but also the need for further validation of resulting weights.

Patterns, trends and methodological associations in the measurement and valuation of childhood health utilities

PURPOSE

To systematically assess patterns and temporal changes in the measurement and valuation of childhood health utilities and associations between methodological factors.

METHODS

Studies reporting childhood health utilities using direct or indirect valuation methods, published by June 2017, were identified through PubMed, Embase, Web of Science, PsycINFO, EconLit, CINAHL, Cochrane Library and PEDE. The following were explored: patterns in tariff application; linear trends in numbers of studies/samples and paediatric cost-utility analyses (CUAs) and associations between them; changes in proportions of studies/samples within characteristic-based categories over pre-specified periods; impact of National Institute for Health and Care Excellence (NICE) guidance on primary UK research and associations between valuation method, age and methodological factors.

RESULTS

335 studies with 3974 samples covering all ICD-10 chapters, 23 valuation methods, 12 respondent types and 42 countries were identified by systematic review. 34.0% of samples using indirect methods compatible with childhood applied childhood-derived tariffs. There was no association between numbers of studies/samples and numbers of CUAs. Compared to 1990-2008, 2009-June 2017 saw a significant fall in the proportion of studies using case series; significant compositional changes across ICD-10 chapters and significantly higher sample proportions using childhood-specific and adult-specific indirect valuation methods, and based on pre-adolescents, self-assessment, self-administration and experienced health states. NICE guidance was weakly effective in promoting reference methods. Associations between valuation method, age and methodological factors were significant.

CONCLUSION

1990-2017 witnessed significant changes in primary research on childhood health utilities. Health technology assessment agencies should note the equivocal effect of methodological guidance on primary research.

The Corrective Approach: Policy Implications of Recent Developments in QALY Measurement Based on Prospect Theory

BACKGROUND AND OBJECTIVES

Common health state valuation methodology, such as time tradeoff (TTO) and standard gamble (SG), is typically applied under several descriptively invalid assumptions, for example, related to linear quality-adjusted life years (QALYs) or expected utility (EU) theory. Hence, the current use of results from health state valuation exercises may lead to biased QALY weights, which may in turn affect decisions based on economic evaluations using such weights. Methods have been proposed to correct responses for the biases associated with different health state valuation techniques. In this article we outline the relevance of prospect theory (PT), which has become the dominant descriptive alternative to EU, for health state valuations and economic evaluations.

METHODS AND RESULTS

We provide an overview of work in this field, which aims to remove biases from QALY weights. We label this "the corrective approach." By quantifying PT parameters, such as loss aversion, probability weighting, and nonlinear utility, it may be possible to correct TTO and SG responses for biases in an attempt to produce more valid estimates of preferences for health states. Through straightforward examples, this article illustrates the effects of this corrective approach and discusses several unresolved issues that currently limit the relevance of corrected weights for policy.

CONCLUSIONS

Suggestions for research addressing these issues are provided. Nonetheless, if validly corrected health state valuations become available, we argue in favor of using these in economic evaluations.

A hybrid modelling approach for eliciting health state preferences: the Portuguese EQ-5D-5L value set

BACKGROUND

The EQ-5D is a generic preference-based quality of life measure considered useful for supporting clinical and policy decisions by providing utility values that can easily be converted into quality-adjusted life years to be integrated in cost-utility economic evaluations. Although the three-level classification system of the EuroQol questionnaire (EQ-5D-3L) is still the most popular preference-based instrument used worldwide, several studies reported a ceiling effect on this version, especially in healthy and/or young individuals. In 2009, the EuroQol Group introduced a five-level EQ-5D, which expands the descriptive system from three to five levels within the same five dimensions. For this version to be used in health economic evaluation, societal values need to be assigned to the 3125 health states generated by this instrument.

OBJECTIVES

The aims of this study were to elicit the EQ-5D-5L health state preferences from the general Portuguese population and to derive the Portuguese value set for the EQ-5D-5L.

METHODS

A representative sample of the Portuguese general population aged above 18 years was stratified by age and gender (n = 1451). Between October 2015 and July 2016, 28 interviewers carried out a series of 1-h-long computer-assisted personal interviews following the EuroQol Valuation Technology protocol. Each interview included the valuation of ten health states using the composite time trade-off (cTTO) and seven pairs of discrete choice experiments (DCEs). A standardized tool for quality control was used to assess the quality of the data as well as direct supervision and cross-examination of 10% of the global sample size. Data from both cTTO and DCE valuation tasks were modelled using a censored heteroskedastic hybrid model.

RESULTS

Interviewers complied with the quality control protocol in providing high-quality valuation data. The hybrid econometric model had consistent and significant parameters. The derived societal values for the Portuguese population ranged from - 0.603 to 1.

CONCLUSION

This study provided the Portuguese value set for the EQ-5D-5L on the basis of a hybrid econometric model using cTTO and DCE data. These results represent the preferences of the Portuguese population and are recommended to inform health decision-making in Portugal.

Development of one general and six country-specific algorithms to assess societal health utilities based on ASAS HI

Objective

Health utilities represent preference values that persons attach to health states. This study aims to develop one general and six country-specific algorithms to calculate societal preference values for health of patients with spondyloarthritis (SpA), as assessed by the disease-specific Assessment of SpondyloArthritis international Society Health Index (ASAS HI).

Methods

A survey was performed in random population samples from six European countries. In a best-worst choice experiment, subjects were asked to indicate repeatedly which of 4 random aspects of the 17-item ASAS HI was were most and least important. Bayesian analysis provided the relative importance of each of the 17 items. To rescale the relative importance scores on the absolute utility scale between 0 and 1, participants additionally completed two lead time trade-off experiments, one for 'severe SpA' and one for 'best health' without SpA. Six country-specific algorithms and one general algorithm were derived. The general algorithm was tested in 199 patients with axial SpA (axSpA).

Results

3039 subjects, mean age 47 years (SD 15) and 52% female completed the experiments. The population's health utility value for SpA varied between - 0.24 for 'worst' SpA (country range -0.35 to 0.03), and 0.88 for 'best' health (country range 0.81 to 0.90). Among 199 patients with axSpA, the mean utility was 0.36 (SD 0.30, range -0.24 to 0.88) and discriminated well between patients having high (Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) ≥ 4) or low (BASDAI < 4) disease activity (0.18 (SD 0.24) vs 0.51(SD 0.27), p<0.01).

Conclusion

One general and six country-specific algorithms are available to convert scores from the ASAS HI into disease-specific societal utility values.

Disability weights for infectious diseases in four European countries: comparison between countries and across respondent characteristics

Background

In 2015, new disability weights (DWs) for infectious diseases were constructed based on data from four European countries. In this paper, we evaluated if country, age, sex, disease experience status, income and educational levels have an impact on these DWs.

Methods

We analyzed paired comparison responses of the European DW study by participants’ characteristics with separate probit regression models. To evaluate the effect of participants’ characteristics, we performed correlation analyses between countries and within country by respondent characteristics and constructed seven probit regression models, including a null model and six models containing participants’ characteristics. We compared these seven models using Akaike Information Criterion (AIC).

Results

According to AIC, the probit model including country as covariate was the best model. We found a lower correlation of the probit coefficients between countries and income levels (range r_s: 0.97–0.99, P < 0.01) than between age groups (range r_s: 0.98–0.99, P < 0.01), educational level (range r_s: 0.98–0.99, P < 0.01), sex (r_s = 0.99, P < 0.01) and disease status (r_s = 0.99, P < 0.01). Within country the lowest correlations of the probit coefficients were between low and high income level (range r_s = 0.89–0.94, P < 0.01).

Conclusions

We observed variations in health valuation across countries and within country between income levels. These observations should be further explored in a systematic way, also in non-European countries. We recommend future researches studying the effect of other characteristics of respondents on health assessment.

Health-related quality of life in patients with uveitis

Background/aims

To measure health-related quality of life (HRQOL) in patients with uveitis using time trade-off (TTO) and standard gamble (SG) methods of direct utility analysis.

Methods

Consecutive patients attending a tertiary referral uveitis clinic were administered standardised, interview-delivered TTO and SG questionnaires and completed the European Quality of Life Five Dimensions Five Level (EQ5D-5L) questionnaire. Clinical data recorded included best-corrected visual acuity, uveitis anatomical and clinical classifications, duration since diagnosis, disease activity, current medication and any ocular or systemic comorbidities.

Results

Two hundred patients with uveitis (124 female, 76 male, median age 54 years) were included. Overall mean TTO utility was 0.831 (95% CI 0.802 to 0.860); mean SG utility was 0.868 (95% CI 0.840 to 0.896) and mean EQ5D-5L utility was 0.742 (95% CI 0.702 to 0.782). There was a negative correlation between visual acuity and mean HRQOL (6/12 or better: TTO 0.86, SG 0.893; 6/15–6/60: TTO 0.662, SG 0.742; worse than 6/60: TTO 0.608, SG 0.712). Poor vision in the better- seeing eye (p=0.004), bilateral disease (p=0.047) and concurrent glaucomatous optic neuropathy (p=0.005) were predictors of poor TTO HRQOL. No correlation was found between HRQOL and duration of diagnosis, a flare of uveitis or being on systemic therapy. Patients with uveitis with poor vision have a TTO value worse than patients with end-stage renal failure on haemodialysis or those with AIDS.

Conclusion

Loss of vision resulting from uveitis is associated with reduced HRQOL. The TTO and SG utility values appear directly dependent on the degree of vision loss and not on the duration of disease or systemic medications.

Head-to-Head Comparison of EQ-5D-3L and EQ-5D-5L Health Values

BACKGROUND

The EQ-5D is a widely used preference-based instrument to measure health-related quality of life. Some methodological drawbacks of its three-level version (EQ-5D-3L) prompted development of a new format (EQ-5D-5L). There is no clear evidence that the new format outperforms the standard version.

OBJECTIVE

The objective of this study was to make a head-to-head comparison of the EQ-5D-3L and EQ-5D-5L in a discrete choice model setting giving special attention to the consistency and logical ordering of coefficients for the attribute levels and to the differences in health-state values.

METHODS

Using efficient designs, 240 pairs of EQ-5D-3L health states and 240 pairs of EQ-5D-5L health states were generated in a pairwise choice format. The study included 3698 Dutch general population respondents, analyzed their responses using a conditional logit model, and compared the values elicited by EQ-5D-3L and EQ-5D-5L for different health states.

RESULTS

No inconsistencies or illogical ordering of level coefficients were observed in either version. The proportion of severe health states with low values was higher in the EQ-5D-5L than in the EQ-5D-3L, and the proportion of mild/moderate states was lower in the EQ-5D-5L than in the EQ-5D-3L. Moreover, differences were observed in the relative weights of the attributes.

CONCLUSION

Overall distribution of health-state values derived from a large representative sample using the same measurement framework for both versions showed differences between the EQ-5D-3L and EQ-5D-5L. However, even small differences in the phrasing (language) of the descriptive system or in the valuation protocol can produce differences in values between these two versions.

Eye tracking to explore attendance in health-state descriptions

INTRODUCTION

A crucial assumption in health valuation methods is that respondents pay equal attention to all information components presented in the response task. So far, there is no solid evidence that respondents are fulfilling this condition. The aim of our study is to explore the attendance to various information cues presented in the discrete choice (DC) response tasks.

METHODS

Eye tracking was used to study the eye movements and fixations on specific information areas. This was done for seven DC response tasks comprising health-state descriptions. A sample of 10 respondents participated in the study. Videos of their eye movements were recorded and are presented graphically. Frequencies were computed for length of fixation and number of fixations, so differences in attendance were demonstrated for particular attributes in the tasks.

RESULTS

All respondents completed the survey. Respondents were fixating on the left-sided health-state descriptions slightly longer than on the right-sided. Fatigue was not observed, as the time spent did not decrease in the final response tasks. The time spent on the tasks depended on the difficulty of the task and the amount of information presented.

DISCUSSION AND CONCLUSION

Eye tracking proved to be a feasible method to study the process of paying attention and fixating on health-state descriptions in the DC response tasks. Eye tracking facilitates the investigation of whether respondents fully read the information in health descriptions or whether they ignore particular elements.

Computer-Assessed Preference-Based Quality of Life in Patients with Spinal Cord Injury

Objectives

Our aims were to (1) measure quality of life (QoL) in spinal cord injury (SCI) patients using different methods and analyze differences; (2) enable targeted treatments by identifying variables that affect QoL; and (3) provide decision-makers with useful data for cost-utility analyses in SCI population.

Methods

Seventy-one participants were enrolled. The computer-based tool UceWeb was used to elicit QoL in terms of utility coefficients, through the standard gamble, time trade-off, and rating scale methods. The SF36 questionnaire was also administered. Statistical analyses were performed to find predictors of QoL among collected variables.

Results

Median values for rating scale, time trade-off, and standard gamble were 0.60, 0.82, and 0.85, respectively. All scales were significantly correlated. Rating scale and SF36 provided similar values, significantly lower than the other methods. Impairment level, male gender, older age, living alone, and higher education were correlated with lower QoL but accounted for only 20% of the variation in utility coefficients.

Conclusions

Demographic and clinical variables are useful to predict QoL but do not completely capture utility coefficients variability. Therefore, direct preference-based utility elicitation should be strengthened. Finally, this is the first study providing data that can be used as a reference for cost-utility analyses in the Italian SCI population.

Estimation of utility weights for major liver diseases according to disease severity in Korea

Background

The global burden of liver diseases, such as hepatocellular carcinoma and liver cirrhosis, is substantial. In this study, we estimated utility weights of liver disease-related health states in the general population using a visual analogue scale (VAS) and the standard gamble (SG) method.

Methods

Depictions of standardized health states related to major liver diseases were developed based on patient education materials and previous publications. To fully reflect disease progression from diagnosis to prognosis, each health state comprised four parts: diagnosis, symptoms, treatment, and progression and prognosis. A total of 407 participants from the Korean general population evaluated the health states using the VAS and SG methods in computer-assisted personal interviews. After excluding illogical responses, mean utility weights were calculated for each health state.

Results

The utility weights for health states were significantly different according to the existence of inconsistency in general. According to the VAS results, the health state with the highest utility was ‘Chronic hepatitis B virus infection’ (0.64), whereas the health state with the lowest utility was ‘Hepatocellular carcinoma that requires palliative therapy’ (0.17). Similarly, the SG results revealed that the health state with the highest utility was ‘Chronic hepatitis B virus infection’ (0.85), and the health state with the lowest utility was ‘Hepatocellular carcinoma that requires palliative therapy’ (0.40).

Conclusions

The estimated utility weights in this study will be useful to measure the burden of liver diseases and evaluate cost-utility of programs for reducing the burden of liver diseases.

Electronic supplementary material

The online version of this article (10.1186/s12876-017-0660-3) contains supplementary material, which is available to authorized users.

Exploring the Reference Point in Prospect Theory: Gambles for Length of Life

Attitude toward risk is an important factor determining patient preferences. Risk behavior has been shown to be strongly dependent on the perception of the outcome as either a gain or a loss. According to prospect theory, the reference point determines how an outcome is perceived. However, no theory on the location of the reference point exists, and for the health domain, there is no direct evidence for the location of the reference point. This article combines qualitative with quantitative data to provide evidence of the reference point in life-year certainty equivalent (CE) gambles and to explore the psychology behind the reference point. The authors argue that goals (aspirations) in life influence the reference point. While thinking aloud, 45 healthy respondents gave certainty equivalents for life-year CE gambles with long and short durations of survival. Contrary to suggestions from the literature, qualitative data argued that the offered certainty equivalent most frequently served as the reference point. Thus, respondents perceived life-year CE gambles as mixed. Framing of the question and goals set in life appeared to be important factors behind the psychology of the reference point. On the basis of the authors' quantitative and qualitative data, they argue that goals alter the perception of outcomes as described by prospect theory by influencing the reference point. This relationship is more apparent for the near future as opposed to the remote future, as goals are mostly set for the near future.

A Note on the Validity and Reliability of Multi-Criteria Decision Analysis for the Benefit-Risk Assessment of Medicines

The comparative evaluation of benefits and risks is one of the most important tasks during the development, market authorization and post-approval pharmacovigilance of medicinal products. Multi-criteria decision analysis (MCDA) has been recommended to support decision making in the benefit-risk assessment (BRA) of medicines. This paper identifies challenges associated with bias or variability that practitioners may encounter in this field and presents solutions to overcome them. The inclusion of overlapping or preference-complementary criteria, which are frequent violations to the assumptions of this model, should be avoided. For each criterion, a value function translates the original outcomes into preference-related scores. Applying non-linear value functions to criteria defined as the risk of suffering a certain event during the study introduces specific risk behaviours in this prescriptive, rather than descriptive, model and is therefore a questionable practice. MCDA uses weights to compare the importance of the model criteria with each other; during their elicitation a frequent situation where (generally favourable) mild effects are directly traded off against low probabilities of suffering (generally unfavourable) severe effects during the study is known to lead to biased and variable weights and ought to be prevented. The way the outcomes are framed during the elicitation process, positively versus negatively for instance, may also lead to differences in the preference weights, warranting an appropriate justification during each implementation. Finally, extending the weighted-sum MCDA model into a fully inferential tool through a probabilistic sensitivity analysis is desirable. However, this task is troublesome and should not ignore that clinical trial endpoints generally are positively correlated.

Preferences for Prostate Cancer Outcomes: A Comparison of the Patient Perspective, the General Population Perspective, and a Population at Risk for Prostate Cancer

OBJECTIVE

To collect disease-specific and generic preference values for three populations.

METHODS

Prostate cancer-specific health states were developed with attributes that varied across five health domains: sexual function, urinary function, bowel function, pain, and fear of the future. Men with prostate cancer, men at risk for prostate cancer, and a sample of the general population assigned value to 18 disease-specific health states using standard gamble (SG) methodology. Study participants also completed the Health Utilities Index (HUI) to obtain generic, community-based preference values to capture their current health rating.

RESULTS

A total of 136 participants were enrolled (n = 43 prostate cancer; n = 40 at risk for prostate cancer; n = 49 general population). Mean HUI mark 3 current health ratings: men with prostate cancer 0.75 ± 0.260; men at risk for prostate cancer 0.77 ± 0.238; general population 0.84 ± 0.178. Mean SG preference values ranged from 0.46 to 0.85 among men with prostate cancer, 0.37 to 0.75 among men at risk for prostate cancer, and 0.32 to 0.81 among the general population group.

CONCLUSIONS

In general, preference values for disease-specific health states using the patient perspective were higher than those for the general population. Generic preference values calculated from the HUI were higher than disease-specific preference values calculated from the SG. The higher values calculated from the HUI, from all three perspectives, indicate that a generic measure may not be sensitive enough to capture the disutility of prostate cancer symptoms, specifically sexual dysfunction, urinary dysfunction, and bowel dysfunction, which are being directly measured in the disease-specific health states.

Valuation of depression co-occurring with a somatic condition: feasibility of the time trade-off task

BACKGROUND

Health state valuations obtained from the general population are used for cost-utility analyses of health-care interventions. Currently, most studies have focused on valuations of somatic conditions, to a much lesser extent of mental states, that is, depression and even less on valuations of depression co-occurring with somatic conditions.

OBJECTIVE

We tested the feasibility of the time trade-off (TTO) task to elicit valuations for depression solitary or co-occurring with a somatic condition. Moreover, we explored person- and state-related factors that may affect valuations.

DESIGN

During semi-structured interviews, 10 individuals (five women, mean age: 36 years) used a TTO task to value vignettes describing mild and severe depression; and mild depression co-occurring with moderate and severe states of cancer, diabetes or heart disease. During valuations, participants were thinking aloud. Feasibility criteria were successful completion and difficulty/concentration (1-10); logical consistency of values; and comprehension of the TTO, based on qualitative analysis of think aloud data. Factors influencing valuations were generated from think aloud data.

RESULTS

Participants reported satisfactory levels of difficulty (mean: 1.9) and concentration (mean: 8.3) and assigned consistent values. Qualitative analysis revealed difficulties with imagining: living with depression for lifetime (n = 4); reaching the age of 80 (n = 6); and living with a somatic condition and mentally healthy (n = 6). Person- and state-related factors, for example perceived susceptibility to depression (n = 4), appeared to affect valuations.

CONCLUSION

Quantitative findings supported feasibility of the valuation protocol, yet qualitative findings indicated that certain task aspects should be readdressed. Factors influencing valuations can be explored to better understand valuations.

Utility scores for vesicoureteral reflux and anti-reflux surgery

BACKGROUND

Management of vesicoureteral reflux (VUR) continues to be controversial. In conditions of uncertainty, decision analytic techniques such as cost-utility analysis (CUA) can help to structure the decision-making process. However, CUA analyses require a "utility," a value between 0 (death) and 1 (perfect health) corresponding to the quality of life associated with a health state. Ideally, utility values are elicited directly from representative community samples, but utilities have not been rigorously measured for pediatric urology conditions.

OBJECTIVES

To elicit utility scores for VUR and open anti-reflux surgery (ARS) from a representative, well-characterized community sample of adults who have been parents.

METHODS

Cross-sectional survey of nationally representative adults who had ever been parents. Each respondent saw one of four descriptions of VUR, with or without continuous antibiotic prophylaxis (CAP) and occurrence of febrile urinary tract infection (UTI). A 6-week postoperative health state following ARS was also assessed. We used the time trade-off (TTO) method to elicit utility scores. Factors associated with utility score were assessed with a multivariate linear regression model.

RESULTS

The survey was completed by 1200 individuals. Data were weighted to adjust for demographic differences between responders and non-responders. Mean age was 52 ± 15 years, 44% were male, and 68% were White. In terms of education, 29% had a college degree or higher. The mean utility score for VUR overall was 0.82 ± 0.28. VUR utility scores did not differ significantly based on inclusion of CAP or UTI in the health state description (p = 0.21). The 6-week postoperative period garnered a utility of 0.71 ± 0.43.

DISCUSSION

Our results showed that VUR has a mean utility score of 0.82, which indicates that the community perceives this condition to be a substantial burden. For comparison, conditions with similar utility scores include compensated hepatitis B-related cirrhosis (0.80) and glaucoma (0.82); conditions with higher utilities include neonatal jaundice (0.99) and transient neonatal neurological symptoms (0.95); and conditions with lower utility scores include severe depression (0.43) and major stroke (0.30). Our results suggest that parents consider the burden associated with VUR to be significant, and that the impact of the condition on families and children is substantial.

CONCLUSIONS

VUR is perceived as having a substantial impact on health-related quality of life, with a utility value of 0.82. However, use of CAP and occurrence of UTI do not seem to affect significantly the community perspective on HRQOL associated with living with VUR.

Do Probability and Certainty Equivalent Techniques Lead to Inconsistent Results? Evidence from Gambles Involving Life-Years and Quality of Life

BACKGROUND

Within the standard gamble approach to the elicitation of health preferences, no previous studies compared probability equivalent (PE) and certainty equivalent (CE) techniques

OBJECTIVE

This study aimed to explore the differences between CE and PE techniques when payoffs are expressed in terms of life-years or quality of life.

METHODS

Individuals were interviewed through both CE and PE techniques within an experimental setting. Inferential statistics and regression analysis where applied to process data. Order and sequence effect were also investigated.

RESULTS

On average, the elicitation technique did not affect individuals' risk attitude significantly. Individuals proved to be risk averse in gambles concerning life-years and risk seekers in those concerning quality of life. No order or sequence effect was observed. Risk premium, measuring the strength of risk attitude as the percentage variation between the individual's estimated PE or CE and the risk neutral PE or CE, was affected by the kind of gamble that the interviewee is presented with. It increased in gambles concerning health profiles, denoting a stronger risk propensity, and decreased in gambles concerning life years, denoting a stronger risk aversion.

CONCLUSION

The choice of the elicitation technique did not affect the individuals' risk attitude significantly, which instead was sensitive to the kind of gamble.

A potential gender bias in assessing quality of life - a standard gamble experiment among university students

BACKGROUND

There are several methodologies that can be used for evaluating patients' perception of their quality of life. Most commonly, utilities are directly elicited by means of either the time-trade-off or the standard-gamble method. In both methods, risk attitudes determine the quality of life values.

METHODS

Quality of life values among 31 Austrian undergraduate students were elicited by means of the standard gamble approach. The impact of several variables such as gender, side job, length of study, and living arrangements on the quality of life were identified using different types of regression techniques (ordinary least squares, generalized linear model, Betafit).

RESULTS

Significant evidence was found that females are associated with a higher quality of life in all specifications of our estimations.

DISCUSSION

The observed gender differences in quality of life can be attributed to a higher degree of risk aversion of women. A higher risk aversion leads to a higher valuation of given health states and a potential gender bias in health economic evaluations. This result could have implications for health policy planners when it comes to budget allocation decisions.

Pain quality of life as measured by utilities

OBJECTIVE

Utilities are values of health-related quality of life (HRQoL) based on patient preference for a health status. The purpose of this study was to compare indirect measures to a directly elicited utility.

DESIGN

Cross-sectional study.

SETTING AND PATIENTS

Emory Spine Center and the Emory Center for Chronic Pain at Crawford Long Hospital. Patients at least 18 years of age with chronic pain, defined as pain that persists beyond the normal time of healing, usually beyond 6 months.

MEASURES

Chronic pain subjects completed a paper-based, self-administered time trade-off (TTO) survey, EQ-5D survey, and a face-to-face (FTF) TTO interview. Current pain severity was graded using the Numeric Rating Scale-11, subsequently stratified into no (0), mild (1-3), moderate (4-6), and severe (7-10) pain.

RESULTS

Paired t test comparing FTF TTO and proxy utility measures stratified by severity revealed FTF TTO utility values significantly higher than EQ-5D utility values for all pain severities (overall mean difference 0.18, standard deviation [SD] 0.30, P < 0.001; Pearson's correlation 0.34, P < 0.0001); FTF TTO utility values were lower than paper TTO utility values, reaching statistical significance for mild and moderate pain (overall mean difference 0.09, SD 0.29, P = 0.0006; Pearson's correlation 0.38, P < 0.0001).

CONCLUSIONS

This study demonstrates that the EQ-5D overestimates, whereas the paper version of TTO underestimates, the impact of pain on HRQoL compared with the directly elicited FTF TTO utility. Our findings provide preliminary evidence that utilities vary by method, and directly elicited utility values differ from indirectly elicited measures.

Qualitative and Quantitative Analysis of Interviewer Help Answering the Time Tradeoff

OBJECTIVES

The time tradeoff (TTO) is an important method to directly obtain health utilities. Challenges of the TTO are, among others, "nontraders" and illogical answers. In TTO interviews, these challenges are resolved by the interviewer. In web-based TTOs, training procedures and logical checks are used based on the views of the researchers. As web-based TTOs will be used more often in the future, we investigated how respondents arrive at their ratings to determine the help they require.

METHODS

In 2 earlier studies performed by this research group, respondents valued 6 EQ-5D states on a TTO. Respondents were asked to think out loud, and all interviews were audiotaped. A random selection of these interviews were transcribed and double-coded by two independent raters, using a priori and inductive coding until saturation was reached. Based on the retrieved mistakes and comments, a list of frequently asked questions (FAQ) was developed.

RESULTS

In total, 91 interviews were coded. In all, 85% made at least 1 mistake, 41% made a misreading/miscalculation, 70% misunderstood the tradeoff, 27% misunderstood the EQ-5D dimensions, 29% misunderstood the scenario, 45% made a comment about the TTO, and 43% expressed frustration. More misunderstandings were reported in the Peeters study, which was performed in a realistic setting, whereas the van Osch study was conducted in a more ideal setting. Misunderstandings of the scenario were mosly reported by patients.

CONCLUSIONS

Almost all respondents need interviewer help. This may have implications for the validity of interviewer-based TTO elicitations when social acceptability bias is an issue or with explicit hypothesis and the interviewer is not blinded. The FAQ list can be used to standardize interviewer help or as a help function in a web-based TTO.

Quality-of-life-adjusted hazard of death: a formulation of the quality-adjusted life-years model of use in benefit-risk assessment

BACKGROUND

Although the quality-adjusted life-years (QALY) model is standard in health technology assessment, quantitative methods are less frequent but increasingly used for benefit-risk assessment (BRA) at earlier stages of drug development. A frequent challenge when implementing metrics for BRA is to weigh the importance of effects on a chronic condition against the risk of severe events during the trial. The lifetime component of the QALY model has a counterpart in the BRA context, namely, the risk of dying during the study.

METHODS

A new concept is presented, the hazard of death function that a subject is willing to accept instead of the baseline hazard to improve his or her chronic health status, which we have called the quality-of-life-adjusted hazard of death.

RESULTS

It has been proven that if assumptions of the linear QALY model hold, the excess mortality rate tolerated by a subject for a chronic health improvement is inversely proportional to the mean residual life.

CONCLUSIONS

This result leads to a new representation of the linear QALY model in terms of hazard rate functions and allows utilities obtained by using standard methods involving trade-offs of life duration to be translated into thresholds of tolerated mortality risk during a short period of time, thereby avoiding direct trade-offs using small probabilities of events during the study, which is known to lead to bias and variability.

Prospect theory in the health domain: a quantitative assessment

It is well-known that expected utility (EU) has empirical deficiencies. Cumulative prospect theory (CPT) has developed as an alternative with more descriptive validity. However, CPT's full function had not yet been quantified in the health domain. This paper is therefore the first to simultaneously measure utility of life duration, probability weighting, and loss aversion in this domain. We observe loss aversion and risk aversion for gains and losses, which for gains can be explained by probabilistic pessimism. Utility for gains is almost linear. For losses, we find less weighting of probability 1/2 and concave utility. This contrasts with the common finding of convex utility for monetary losses. However, CPT was proposed to explain choices among lotteries involving monetary outcomes. Life years are arguably very different from monetary outcomes and need not generate convex utility for losses. Moreover, utility of life duration reflects discounting, causing concave utility.

Time trade-off: one methodology, different methods

There is no scientific consensus on the optimal specification of the time trade-off (TTO) task. As a consequence, studies using TTO to value health states may share the core element of trading length of life for quality of life, but can differ considerably on many other elements. While this pluriformity in specifications advances the understanding of TTO from a methodological point of view, it also results in incomparable health state values. Health state values are applied in health technology assessments, and in that context comparability of information is desired. In this article, we discuss several alternative specifications of TTO presented in the literature. The defining elements of these specifications are identified as being either methodological, procedural or analytical in nature. Where possible, it is indicated how these elements affect health state values (i.e., upward or downward). Finally, a checklist for TTO studies is presented, which incorporates a list of choices to be made by researchers who wish to perform a TTO task. Such a checklist enables other researchers to align methodologies in order to enhance the comparability of health state values.

Common values in assessing health outcomes from disease and injury: disability weights measurement study for the Global Burden of Disease Study 2010

BACKGROUND

Measurement of the global burden of disease with disability-adjusted life-years (DALYs) requires disability weights that quantify health losses for all non-fatal consequences of disease and injury. There has been extensive debate about a range of conceptual and methodological issues concerning the definition and measurement of these weights. Our primary objective was a comprehensive re-estimation of disability weights for the Global Burden of Disease Study 2010 through a large-scale empirical investigation in which judgments about health losses associated with many causes of disease and injury were elicited from the general public in diverse communities through a new, standardised approach.

METHODS

We surveyed respondents in two ways: household surveys of adults aged 18 years or older (face-to-face interviews in Bangladesh, Indonesia, Peru, and Tanzania; telephone interviews in the USA) between Oct 28, 2009, and June 23, 2010; and an open-access web-based survey between July 26, 2010, and May 16, 2011. The surveys used paired comparison questions, in which respondents considered two hypothetical individuals with different, randomly selected health states and indicated which person they regarded as healthier. The web survey added questions about population health equivalence, which compared the overall health benefits of different life-saving or disease-prevention programmes. We analysed paired comparison responses with probit regression analysis on all 220 unique states in the study. We used results from the population health equivalence responses to anchor the results from the paired comparisons on the disability weight scale from 0 (implying no loss of health) to 1 (implying a health loss equivalent to death). Additionally, we compared new disability weights with those used in WHO's most recent update of the Global Burden of Disease Study for 2004.

FINDINGS

13,902 individuals participated in household surveys and 16,328 in the web survey. Analysis of paired comparison responses indicated a high degree of consistency across surveys: correlations between individual survey results and results from analysis of the pooled dataset were 0·9 or higher in all surveys except in Bangladesh (r=0·75). Most of the 220 disability weights were located on the mild end of the severity scale, with 58 (26%) having weights below 0·05. Five (11%) states had weights below 0·01, such as mild anaemia, mild hearing or vision loss, and secondary infertility. The health states with the highest disability weights were acute schizophrenia (0·76) and severe multiple sclerosis (0·71). We identified a broad pattern of agreement between the old and new weights (r=0·70), particularly in the moderate-to-severe range. However, in the mild range below 0·2, many states had significantly lower weights in our study than previously.

INTERPRETATION

This study represents the most extensive empirical effort as yet to measure disability weights. By contrast with the popular hypothesis that disability assessments vary widely across samples with different cultural environments, we have reported strong evidence of highly consistent results.

FUNDING

Bill & Melinda Gates Foundation.

Converting condition-specific measures into preference-based outcomes for use in economic evaluation

Quality-adjusted life-years (QALYs) play an important role in reimbursement decisions when one of the criteria is the cost-effectiveness of the health technology. While for many generic QALYs (e.g., based on the EQ-5D) are viewed as the gold standard, there has been a considerable increase in interest in using condition-specific data to generate QALYs. There are two main methods: mapping from the condition-specific data to a generic health-related quality of life measure; and direct valuation of condition-specific health states. Whether one believes condition-specific data are useful even if generic QALY data are available, or simply that condition-specific data are helpful in the absence of generic measures of health-related quality of life, it is timely to review recent research activity directed at making greater use of condition-specific data to inform assessments of cost-effectiveness.