The QALY Model and Individual Preferences for Health States and Health Profiles over Time: A Systematic Review of the Literature

Justification of principles for healthcare priority setting: the relevance and roles of empirical studies exploring public values

How should scarce healthcare resources be distributed? This is a contentious issue that became especially pressing during the pandemic. It is often emphasised that studies exploring public views about this question provide valuable input to the issue of healthcare priority setting. While there has been a vast number of such studies it is rarely articulated, more specifically, what the results from these studies would mean for the justification of principles for priority setting. On the one hand, it seems unreasonable that public values would straightforwardly decide the ethical question of how resources should be distributed. On the other hand, in a democratic society, it seems equally unreasonable that they would be considered irrelevant for this question. In this paper we draw on the notion of reflective equilibrium and discuss the relevance and roles that empirical studies may plausibly have for justification in priority setting ethics. We develop a framework for analysing how different kinds of empirical results may have different kinds of implications for justification.

Reference-dependent age weighting of quality-adjusted life years

People do not only care about maximizing health gains but also about their distribution. For example, they give more weight to younger patients than older patients. This pilot study aims to investigate if age weighting is reinforced by loss aversion if young people are falling behind one's perceived 'normal' quality of life (QoL), while older people do not. We apply a person trade-off method in a large representative sample (n = 990) to estimate age weighting factors. We also measure QoL levels that individuals regard as 'normal' for different ages, serving as reference points. We observe a considerable amount of age weighting, with 20-year-old patients on average receiving 1.7 times as much weight as 80-year-old patients. Perceived 'normal' QoL rapidly decreases with age of a patient. Older people are more optimistic about what constitutes 'normal QoL' than younger people, but they express a faster decline in normal QoL due to aging. Respondents who view all improvements to be gain enlarging show the least age weighting, but loss aversion cannot explain the results. Still, one's age-related reference level is an important predictor of age weights. Given the explorative nature of this study, further studies are called for to generate more robust evidence.

Moving to Personalized Medicine Requires Personalized Health Plans

When individuals, families, and employers select health plans in the United States, they are typically only shown the financial structure of the plans and their provider networks. This variation in financial structure can lead patients to have health plans aligned with their financial needs, but not with their underlying nonfinancial preferences. Compounding the challenge is the fact that managed care organizations have historically used a combination of population-level budget impact models, cost-effectiveness analyses, medical necessity criteria, and current medical consensus to make coverage decisions. This approach to creating and presenting health plan options does not consider heterogeneity in patient and family preferences and values, as it treats populations as uniform. Similarly, it does not consider that there are some situations in which patients are price-insensitive. We seek to highlight the challenges posed by presenting health plans to patients in strictly financial terms, and to call for more consideration of nonfinancial patient preferences in the health plan design and selection process.

Cost effectiveness and health-related quality of life of chemoradiotherapy versus radiation therapy alone in elderly head and neck cancer patients

Purpose

Radiotherapy (RT) constitutes a mainstay in the treatment of elderly patients with head and neck cancer (HNC), but use of simultaneous chemoradiotherapy (CRT) remains controversial. We have conducted a prospective analysis based on real-world patient data to examine the health-related quality of life (HRQoL) and cost effectiveness (CE) of CRT vs. RT in elderly HNC patients.

Methods

Eligible participants ≥ 65 years treated in a large tertiary cancer center between July 2019 and February 2020 who completed the validated EQ-5D-5L questionnaire (health state index [HI] and visual analog scale [VAS]) before and after RT were included. CE referred to direct medical costs, including diagnosis-related group (DRG)-based billings for inpatients and uniform assessment standard (EBM)-based costs for outpatients. The primary endpoint was cost (euros [€]) per quality-adjusted life year (QALY). The incremental cost-effectiveness ratios (ICERs) were calculated. Costs and QALYs were not discounted for short overall survival (OS).

Results

Baseline HRQoL was 0.878 (±0.11) in the CRT group and 0.857 (±0.17) in the RT group. Upon completion of therapy, HRQoL amounted to 0.849 (±0.14) in the CRT and 0.850 (±0.13) in the RT group. The mean treatment-related cost in the CRT cohort was €22,180.17 (±8325.26) vs. €18,027.87 (±26,022.48) in the RT group. The corresponding QALYs amounted to 2.62 in the CRT and 1.91 in the RT groups. The ICER was €5848.31.

Conclusion

This is the first analysis from the German health care system demonstrating that the addition of chemotherapy to RT for selected elderly HNC patients is cost effective and not associated with a significant HRQoL decline.

A systematic literature review of disability weights measurement studies: evolution of methodological choices

Background

The disability weight is an essential factor to estimate the healthy time that is lost due to living with a certain state of illness. A 2014 review showed a considerable variation in methods used to derive disability weights. Since then, several sets of disability weights have been developed. This systematic review aimed to provide an updated and comparative overview of the methodological design choices and surveying techniques that have been used in disability weights measurement studies and how they evolved over time.

Methods

A literature search was conducted in multiple international databases (early-1990 to mid-2021). Records were screened according to pre-defined eligibility criteria. The quality of the included disability weights measurement studies was assessed using the Checklist for Reporting Valuation Studies (CREATE) instrument. Studies were collated by characteristics and methodological design approaches. Data extraction was performed by one reviewer and discussed with a second.

Results

Forty-six unique disability weights measurement studies met our eligibility criteria. More than half (n = 27; 59%) of the identified studies assessed disability weights for multiple ill-health outcomes. Thirty studies (65%) described the health states using disease-specific descriptions or a combination of a disease-specific descriptions and generic-preference instruments. The percentage of studies obtaining health preferences from a population-based panel increased from 14% (2004–2011) to 32% (2012–2021). None of the disability weight studies published in the past 10 years used the annual profile approach. Most studies performed panel-meetings to obtain disability weights data.

Conclusions

Our review reveals that a methodological uniformity between national and GBD disability weights studies increased, especially from 2010 onwards. Over years, more studies used disease-specific health state descriptions in line with those of the GBD study, panel from general populations, and data from web-based surveys and/or household surveys. There is, however, a wide variation in valuation techniques that were used to derive disability weights at national-level and that persisted over time.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13690-022-00860-z.

Economic evaluation of process utility: elucidating preferences for a non-invasive procedure to treat restenosis

BACKGROUND

In health economic evaluation, utility associated with a health state is outcome-oriented and usually measured using the QALY methodology. Even though there is consistent evidence of utility not only being derived from outcomes but also from procedures, process utility has not been fully integrated in QALY calculations. The aim of this paper is twofold: first, to provide evidence of process utility associated with an alternative treatment to angioplasty, and second, to estimate a monetary value of such process utility using the willingness to pay (WTP) approach.

METHODS

A total of 1514 people were polled on their WTP to avoid angioplasty to have a drug-eluting stent (DES) implanted. WTP is estimated with a contingent valuation (CV) survey. Individuals are also asked if they would be WTP for a non-invasive procedure with similar results being achieved. WTP responses were analyzed using a double bounded (DB) logit model.

RESULTS

Most of the participants showed positive preferences for avoiding angioplasty, with an estimated mean WTP of €5692.87. Using QALY gains for avoiding angioplasty, varying from 0.0035 to 0.08 QALYs, our WTP estimate imply monetary values per QALY that range from €71,160.87 to €1,626,534.28.

DISCUSSION

A WTP of €5692.87 to avoid angioplasty imply a monetary value per QALY that greatly exceed the cost per QALY thresholds established in different countries to consider health programs as beneficial to society. Our results reflect how different methodologies for HTA may lead to different conclusions. From the ICER perspective, the cost that would make the treatment with pills option cost-effective, using a threshold of €40,000/QALY, would be €224. However, a cost-benefit approach could support health programs even with a higher cost.

CONCLUSION

WTP methodology captures outcome and process factors related to angioplasty as our WTP estimations are non-significantly different for the costs of angioplasty. WTP approach must be considered as a genuine alternative to QALY approaches to value process utility.

A Head-to-Head Comparison of the Standard Quality-Adjusted Life Year Model With the Annual Profile Model

OBJECTIVES

The standard quality-adjusted life year (QALY) model (SQM) assumes time-utility independence within constant health states and additive independence when health varies over time. The validity of SQM has been challenged through reported violations of these assumptions. An alternative approach that relaxes these assumptions is to assign a single valuation to an entire health profile: an integral assessment of disease severity over time. Here, we compare SQM with the annual profile model (APM) and test SQM for additive independence.

METHODS

Eighty-two respondents valued 6 episodic conditions, including 4 of short duration, with SQM and APM, using the time trade-off method. Inter-rater reliability was assessed using intraclass correlation coefficients. Face validity was tested by asking respondents how well they were able to imagine the health states under SQM and APM. We calculated SQM QALY values for a 1-year time period, allowing for a direct comparison with APM values. For the short-term conditions we expected higher QALY values for SQM, violating additive independence.

RESULTS

APM showed higher interrater reliability (intraclass correlation coefficient of 0.53 vs 0.18, respectively) and better face validity than SQM, with 6% (APM) vs 21% (SQM) of all respondents reporting difficulties. Additive independence of SQM was violated in 5 of the 6 conditions (including the 4 short duration health states), with higher QALY values under SQM (mean difference 0.04).

CONCLUSION

The impact of short-term conditions is systematically underestimated under SQM when compared to a health profile model. APM is a less restrictive model and demonstrates better validity.

Needs and cost-effectiveness in health care priority setting

How to balance the maximization of health and concerns for the worse off remains a challenge for health care decision makers when setting priorities. In regulatory guidelines these concerns are typically specified in terms of priority setting according to needs and priority setting according to cost-effectiveness. Still, it is often unclear when and why needs and cost-effectiveness diverge or overlap as guiding priority setting principles in practice. We conduct a comparative analysis of need and cost-effectiveness in the context of health care priority setting. Based on theories of distributive justice we specify three normative interpretations of need and explicate how these relate to the normative basis for cost-effectiveness analysis. Using priority-setting dilemmas we then move on to explicate when and why need and cost-effectiveness diverge as priority-setting principles. We find that: (i) although principles of need and cost-effectiveness may recommend the same allocation of resources the underlying reason for an allocation is different; (ii) while they both may give weight to patients who are worse off they do so in different ways and to different degree; and (iii) whereas cost-effectiveness clearly implies the aggregation of benefits across individuals principles of needs give no guidance with regard to if, and if so, how needs should be aggregated. Priority setting according to needs or cost-effectiveness does not necessarily recommend different allocations of resources. Thus, the normative conflict between them, often highlighted in practice, seems exaggerated. For health policy this is important knowledge because unclear conceptions may obstruct an informed public discussion. Moreover, if decision-makers are to properly account for both principles they need to recognize the inconsistencies as well as similarities between the two.

The Psychometric Properties of a Self-Administered, Open-Source Module for Valuing Metastatic Epidural Spinal Cord Compression Utilities

INTRODUCTION

Web surveys are often used for utility valuation. Typically, custom utility valuation tools that have not undergone psychometric evaluation are used.

OBJECTIVES

This study aimed to determine the psychometric properties of a metastatic epidural spinal cord compression (MESCC) module run on a customizable open-source, internet-based, self-directed utility valuation platform (Self-directed Online Assessment of Preferences [SOAP]).

METHODS

Individuals accompanying patients to the emergency department waiting room in Ottawa, Canada, were recruited. Participants made SOAP MESCC health state valuations in the waiting room and 48 h later at home. Validity, agreement reliability, and responsiveness were measured by logical consistency of responses, smallest detectable change, the interclass correlation coefficient, and Guyatt's responsiveness index, respectively.

RESULTS

Of 285 participants who completed utility valuations, only 113 (39.6%) completed the re-test. Of these 113 participants, 92 (81.4%) provided valid responses on the first test and 75 (66.4%) provided valid responses on the test and re-test. Agreement for all groups of health states was adequate, since their smallest detectable change was less than the minimal clinically important difference. The mean interclass correlation coefficients for all health states were > 0.8, indicating at least substantial reliability. Guyatt's responsiveness indices all exceeded 0.80, indicating a high level of responsiveness.

CONCLUSIONS

To our knowledge, this is the first validated open-source, web-based, self-directed utility valuation module. We have demonstrated the SOAP MESCC module is valid, reproducible, and responsive for obtaining ex ante utilities. Considering the successful psychometric validation of the SOAP MESCC module, other investigators can consider developing modules for other diseases where direct utility valuation is needed.

Additive Multicriteria Decision Analysis Models: Misleading Aids for Life-Critical Shared Decision Making

Background. There is growing interest in multicriteria decision analysis (MCDA) for shared decision making (SDM). A distinguishing feature is that a preferred treatment should extend years of life and/or improve health-related quality of life (HRQL). Additive MCDA models are inadequate for the task. A plethora of MCDA models exist, each claiming that it can correctly solve real-world problems. However, most were developed in nonhealth fields and rely on additive models. This makes the problem of choosing an MCDA model as an aid for SDM a challenging and urgent one. Methods. A published 2017 MCDA of a hypothetical prostate cancer patient is used as a case in point of how not to do and how to do MCDA for SDM. We critically review it and analyze it using several additive linear MCDA models with years of life and HRQL as attributes and the linear quality-adjusted life-year (QALY) model. The following simple reasonableness test is presented for applicability of a method as an aid for SDM: Can a treatment that causes premature death trump a treatment that causes acceptable adverse effects? Results. Additive MCDA models and the linear QALY recommend significantly different alternatives. Additive MCDA models fail the proposed reasonableness test; the linear QALY model passes. Conclusions. MCDA possesses a strong craft element in addition to its technical aspects. MCDA practitioners and clinicians need to understand model limitations to choose models appropriate to the context. Additive MCDA models are inadequate for life-critical SDM. We advocate QALY models with additional research for increased realism as a tool for SDM.

Against proportional shortfall as a priority-setting principle

As the demand for healthcare rises, so does the need for priority setting in healthcare. In this paper, I consider a prominent priority-setting principle: proportional shortfall. My purpose is to argue that proportional shortfall, as a principle, should not be adopted. My key criticism is that proportional shortfall fails to consider past health.Proportional shortfall is justified as it supposedly balances concern for prospective health while still accounting for lifetime health, even though past health is deemed irrelevant. Accounting for this lifetime perspective means that the principle may indirectly consider past health by accounting for how far an individual is from achieving a complete, healthy life. I argue that proportional shortfall does not account for this lifetime perspective as it fails to incorporate the fair innings argument as originally claimed, undermining its purported justification.I go on to demonstrate that the case for ignoring past health is weak, and argue that past health is at least sometimes relevant for priority-setting decisions. Specifically, when an individual's past health has a direct impact on current or future health, and when one individual has enjoyed significantly more healthy life years than another.Finally, I demonstrate that by ignoring past illnesses, even those entirely unrelated to their current illness, proportional shortfall can lead to instances of double jeopardy, a highly problematic implication. These arguments give us reason to reject proportional shortfall.

Challenges in Valuing Temporary Health States for Economic Evaluation: A Review of Empirical Applications of the Chained Time Trade-Off Method

BACKGROUND

The time trade-off (TTO) technique is commonly used to elicit health state utilities. Nevertheless, when the health states being valued are temporary, the TTO approach may be unsuitable. A variant of TTO- chained TTO-has been suggested to be used when the health states are temporary, but little research has been done on how chained TTO should be conducted.

OBJECTIVES

To systematically review the use of chained TTO in valuing temporary health states.

METHODS

A systematic literature search was conducted using the following major databases: Ovid MEDLINE(R), Embase, EBM Reviews, and PsycINFO. Abstracts (full articles if necessary) were screened by two independent reviewers, with a third reviewer resolving any disagreements.

RESULTS

The resulting number of articles for review was low (n = 9). All the reviewed studies used face-to-face interviews, most had small sample sizes (<100), and all studies valued a small number of health states (<7), with time horizons typically ranging from 4 weeks to 1 year. All studies discussed methodological issues of using chained TTO, and some compared the results with those generated using other preference elicitation methods.

CONCLUSIONS

Chained TTO appears to be feasible, consistent, and responsive and allows the valuation of temporary health states that would improve the efficiency and accuracy of decision making in health and health care. Nevertheless, the evidence is limited due to the low number of relevant studies in the literature. Further research is needed to examine the performance and validity of chained TTO compared with conventional TTO in the valuation of temporary health states.

The Impact of Different DCE-Based Approaches When Anchoring Utility Scores

BACKGROUND

Discrete choice experiments (DCEs) have been proposed as a method to estimate utility weights for health states within utility instruments. However, the most appropriate method to anchor the utility values on the full health to dead quality-adjusted life year (QALY) scale remains uncertain. We test four approaches to anchoring in which dead is valued at zero and full health at one.

METHODS

We use data from two DCEs valuing EQ-5D-3L and EQ-5D-5L health states, which presented pairs of health profiles with an associated duration, and a dead option. The approaches to anchoring the results on the required scale were (1) using only preferences between non-dead health profiles; (2) including the dead data, treating it as a health profile with zero duration; (3) explicitly modelling both duration and dead; and (4) using the preferences regarding the dead health state as an external anchor subsequent to the estimation of approach 1.

RESULTS

All approaches lead to differences in the scale of utility decrements, but not the ranking of EQ-5D health states. The models differ in their ability to predict preferences around dead health states, and the characteristics of the value sets in terms of their range and the proportion of states valued as worse than dead.

DISCUSSION

Appropriate anchoring of DCEs with or without complementary time trade-off (TTO) data remains unresolved, and the method chosen will impact on health resource allocation decision making employing the value sets.

Applications of the Capability Approach in the Health Field: A Literature Review

The primary aims of this review are to document capability applications in the health field and to explore the objectives and decision-rules of studies measuring capability more broadly. Relevant studies are identified using a literature search strategy known as "comprehensive pearl growing". All studies with a primary focus on health are assessed individually, whilst a summary narrative analysis of the full review examines the objectives of capability studies. Four distinct groups in the health field are identified in the review: (1) physical activity and diet; (2) patient empowerment; (3) multidimensional poverty and (4) assessments of health and social care interventions. Different approaches to applying mixed methods, selecting capability dimensions and weighting capabilities are found across studies. There is a noticeable non-reliance on health status as a sole indicator of capability in health. In terms of objectives of studies measuring capability, although there is a lack of consistency, an objective related to sufficiency of capabilities appeared most often in the studies found in this review. Even though one of the appeals of the capability perspective is its underspecified nature, this review highlights the challenge of finding a coherent alternative to more established approaches of evaluation.

The impact of social support at home on health-related quality of life among veterans with spinal cord injury participating in a supported employment program

PURPOSE

To investigate the impact of social support at home on health-related quality of life (HRQOL) as measured by the VR-6D utility index for spinal cord injury (SCI) veterans participating in a program of supported employment (SE).

METHODS

We calculated a preference-based utility index called the VR-6D from the responses from a 36-item instrument called the VR-36. We estimated a growth curve model to examine the change in the VR-6D utility index over time adjusting for social support status, demographics, and chronic comorbidities.

RESULTS

Study participants experienced an increase in HRQOL over time. The initial level and the rate of increase in HRQOL varied by groups based on their support status. The rate of increase in HRQOL diminished over time. Participants reporting no support at home experienced lower initial HRQOL but reached the same level of those who reported having support at home by the ninth month of follow-up. Quality-adjusted life-years, as measured by the area under the curves, were approximately the same for both groups after 2 years.

CONCLUSIONS

Differences in the rate of change in HRQOL by support status have important implications for evaluations of SE programs. Participants in this program of SE experienced improvement in HRQOL beyond 12 months and extending to 2 years. Follow-up times for evaluations should extend beyond 12 months to assess complete improvements in HRQOL. Future comparison groups in comparative effectiveness evaluations of SE need to be balanced carefully on support status in addition to other factors.

Public views on principles for health care priority setting: findings of a European cross-country study using Q methodology

Resources available to the health care sector are finite and typically insufficient to fulfil all the demands for health care in the population. Decisions must be made about which treatments to provide. Relatively little is known about the views of the general public regarding the principles that should guide such decisions. We present the findings of a Q methodology study designed to elicit the shared views in the general public across ten countries regarding the appropriate principles for prioritising health care resources. In 2010, 294 respondents rank ordered a set of cards and the results of these were subject to by-person factor analysis to identify common patterns in sorting. Five distinct viewpoints were identified, (I) "Egalitarianism, entitlement and equality of access"; (II) "Severity and the magnitude of health gains"; (III) "Fair innings, young people and maximising health benefits"; (IV) "The intrinsic value of life and healthy living"; (V) "Quality of life is more important than simply staying alive". Given the plurality of views on the principles for health care priority setting, no single equity principle can be used to underpin health care priority setting. Hence, the process of decision making becomes more important, in which, arguably, these multiple perspectives in society should be somehow reflected.

Review of disability weight studies: comparison of methodological choices and values

INTRODUCTION

The disability-adjusted life year (DALY) is widely used to assess the burden of different health problems and risk factors. The disability weight, a value anchored between 0 (perfect health) and 1 (equivalent to death), is necessary to estimate the disability component (years lived with disability, YLDs) of the DALY. After publication of the ground-breaking Global Burden of Disease (GBD) 1996, alternative sets of disability weights have been developed over the past 16 years, each using different approaches with regards to the panel, health state description, and valuation methods. The objective of this study was to review all studies that developed disability weights and to critically assess the methodological design choices (health state and time description, panel composition, and valuation method). Furthermore, disability weights of eight specific conditions were compared.

METHODS

Disability weights studies (1990¿2012) in international peer-reviewed journals and grey literature were identified with main inclusion criteria being that the study assessed DALY disability weights for several conditions or a specific group of illnesses. Studies were collated by design and methods and evaluation of results.

RESULTS

Twenty-two studies met the inclusion criteria of our review. There is considerable variation in methods used to derive disability weights, although most studies used a disease-specific description of the health state, a panel that consisted of medical experts, and nonpreference-based valuation method to assess the values for the majority of the disability weights. Comparisons of disability weights across 15 specific disease and injury groups showed that the subdivision of a disease into separate health states (stages) differed markedly across studies. Additionally, weights for similar health states differed, particularly in the case of mild diseases, for which the disability weight differed by a factor of two or more.

CONCLUSIONS

In terms of comparability of the resulting YLDs, the global use of the same set of disability weights has advantages, though practical constraints and intercultural differences should be taken into account into such a set.

The better than dead method: feasibility and interpretation of a valuation study

BACKGROUND

Traditionally, the valuation of health states worse than being dead suffers from two problems: [1] the use of different elicitation methods for positive and negative values, necessitating arbitrary transformations to map negative to positive values; and [2] the inability to quantify that values are time dependent. The Better than Dead (BTD) method is a health-state valuation method where states with a certain duration are compared with being dead. It has the potential to overcome these problems.

OBJECTIVES

To test the feasibility of the BTD method to estimate values for the EQ-5D system.

METHODS

A representative sample of 291 Dutch respondents (aged 18-45 years) was recruited. In a web-based questionnaire, preferences were elicited for a selection of 50 different health states with six durations between 1 and 40 years. Random-effects models were used to estimate the effects of socio-demographic and experimental variables, and to estimate values for the EQ-5D. Test-retest reliability was assessed in 41 respondents.

RESULTS

Important determinants for BTD were a religious life stance [odds ratio 4.09 (2.00-8.36)] and the educational level. The fastest respondents more often preferred health-state scenarios to being dead and had lower test-retest reliability (0.45 versus 0.77 and 0.84 for fast, medium and slow response times, respectively). The results showed a small number of so-called maximal endurable time states.

CONCLUSION

Valuating health states using the BTD method is feasible and reliable. Further research should explore how the experimental setting modifies how values depend on time.

Calibration of quality-adjusted life years for oncology clinical trials

CONTEXT

Quality-adjusted life year (QALY) estimation is a well-known but little used technique to compare survival adjusted for complications. Lack of calibration and interpretation guidance hinders implementation of QALY analyses.

OBJECTIVES

We conducted simulation studies to assess the impact of differences in survival, toxicity rates, and utility values on QALY results.

METHODS

Survival comparisons used both log-rank and Wilcoxon testing. We examined power considerations for a North Central Cancer Treatment Group Phase III lung cancer clinical trial (89-20-52).

RESULTS

Sample sizes of 100 events per treatment have low power to generate a statistically significant difference in QALYs unless the toxicity rate is 44% higher in one arm. For sample sizes of 200 per arm and equal survival times, toxicity needs to be at least 38% more in one arm for the result to be statistically significant, using a utility of 0.3 for days with toxicity. Sample sizes of 300 (500)/arm provide 80% power if there is a 31% (25%) toxicity difference. If the overall survival hazard ratio between the two treatment arms is 1.25, then samples of at least 150 patients and 13% increased toxicity are necessary to have 80% power to detect QALY differences. In study 89-20-52, there was only 56% power to determine the statistical significance of the observed QALY differences, clarifying the enigmatic conclusion of no statistically significant difference in QALY despite an observed 14.5% increase in toxicity between treatments.

CONCLUSION

This calibration allows researchers to interpret the clinical significance of QALY analyses and facilitates QALY inclusion in clinical trials through improved study design.

Testing a discrete choice experiment including duration to value health states for large descriptive systems: addressing design and sampling issues

There is interest in the use of discrete choice experiments that include a duration attribute (DCETTO) to generate health utility values, but questions remain on its feasibility in large health state descriptive systems. This study examines the stability of DCETTO to estimate health utility values from the five-level EQ-5D, an instrument with depicts 3125 different health states. Between January and March 2011, we administered 120 DCETTO tasks based on the five-level EQ-5D to a total of 1799 respondents in the UK (each completed 15 DCETTO tasks on-line). We compared models across different sample sizes and different total numbers of observations. We found the DCETTO coefficients were generally consistent, with high agreement between individual ordinal preferences and aggregate cardinal values. Keeping the DCE design and the total number of observations fixed, subsamples consisting of 10 tasks per respondent with an intermediate sized sample, and 15 tasks with a smaller sample provide similar results in comparison to the whole sample model. In conclusion, we find that the DCETTO is a feasible method for developing values for larger descriptive systems such as EQ-5D-5L, and find evidence supporting important design features for future valuation studies that use the DCETTO.

Valuing the health states associated with Chlamydia trachomatis infections and their sequelae: a systematic review of economic evaluations and primary studies

OBJECTIVES

Economic evaluations of interventions to prevent and control sexually transmitted infections such as Chlamydia trachomatis are increasingly required to present their outcomes in terms of quality-adjusted life-years using preference-based measurements of relevant health states. The objectives of this study were to critically evaluate how published cost-effectiveness studies have conceptualized and valued health states associated with chlamydia and to examine the primary evidence available to inform health state utility values (HSUVs).

METHODS

A systematic review was conducted, with searches of six electronic databases up to December 2012. Data on study characteristics, methods, and main results were extracted by using a standard template.

RESULTS

Nineteen economic evaluations of relevant interventions were included. Individual studies considered different health states and assigned different values and durations. Eleven studies cited the same source for HSUVs. Only five primary studies valued relevant health states. The methods and viewpoints adopted varied, and different values for health states were generated.

CONCLUSIONS

Limitations in the information available about HSUVs associated with chlamydia and its complications have implications for the robustness of economic evaluations in this area. None of the primary studies could be used without reservation to inform cost-effectiveness analyses in the United Kingdom. Future debate should consider appropriate methods for valuing health states for infectious diseases, because recommended approaches may not be suitable. Unless we adequately tackle the challenges associated with measuring and valuing health-related quality of life for patients with chlamydia and other infectious diseases, evaluating the cost-effectiveness of interventions in this area will remain problematic.

Introducing the composite time trade-off: a test of feasibility and face validity

INTRODUCTION

This study was designed to test the feasibility and face validity of the composite time trade-off (composite TTO), a new approach to TTO allowing for a more consistent elicitation of negative health state values.

METHODS

The new instrument combines a conventional TTO to elicit values for states regarded better than dead and a lead-time TTO for states worse than dead.

RESULTS

A total of 121 participants completed the composite TTO for ten EQ-5D-5L health states. Mean values ranged from -0.104 for health state 53555 to 0.946 for 21111. The instructions were clear to 98 % of the respondents, and 95 % found the task easy to understand, indicating feasibility. Further, the average number of steps taken in the iteration procedure to achieve the point of indifference in the TTO and the average duration of each task were indicative of a deliberate cognitive process.

CONCLUSION

Face validity was confirmed by the high mean values for the mild health states (>0.90) and low mean values for the severe states (<0.42). In conclusion, this study demonstrates the feasibility and face validity of the composite TTO in a face-to-face standardized computer-assisted interview setting.

Lead time TTO: leading to better health state valuations?

Preference elicitation tasks for better than dead (BTD) and worse than dead (WTD) health states vary in the conventional time trade-off (TTO) procedure, casting doubt on uniformity of scale. 'Lead time TTO' (LT-TTO) was recently introduced to overcome the problem. We tested different specifications of LT-TTO in comparison with TTO in a within-subject design. We elicited preferences for six health states and employed an intertemporal ranking task as a benchmark to test the validity of the two methods. We also tested constant proportional trade-offs (CPTO), while correcting for discounting, and the effect of extending the lead time if a health state is considered substantially WTD. LT-TTO produced lower values for BTD states and higher values for WTD states. The validity of CPTO varied across tasks, but it was higher for LT-TTO than for TTO. Results indicate that the ratio of lead time to disease time has a greater impact on results than the total duration of the time frame. The intertemporal ranking task could not discriminate between TTO and LT-TTO.

Inquiry into the relationship between equity weights and the value of the QALY

BACKGROUND

A commonly held view of the decision rule in economic evaluations in health care is that the final incremental cost-effectiveness ratio needs to be judged against some threshold, which is equal for all quality-adjusted life-year (QALY) gains. This reflects the assumption that "a QALY is a QALY" no matter who receives it, or the equity notion that all QALY gains are equally valuable, regardless of the context in which they are realized. If such an assumption does not adequately reflect the distributional concerns in society, however, different thresholds could be used for different QALY gains, whose relative values can be seen as "equity weights."

AIM

Our aim was to explore the relationship between equity or distributional concerns and the social value of QALYs within the health economics literature. In light of the empirical interest in equity-related concerns as well as the nature and height of the incremental cost-effectiveness ratio threshold, this study investigates the "common ground" between the two streams of literature and considers how the empirical literature estimating the incremental cost-effectiveness ratio threshold treats existing distributional considerations.

Who are the patients with early arthritis with worse than death scores on the EQ-5D? Results from the ESPOIR cohort

OBJECTIVES

The EQ-5D is a five-dimension multi-attribute questionnaire widely used to calculate quality-adjusted life-year scores. We aimed to describe patients with early arthritis (EA) and EQ-5D < 0, a state worse than death, at baseline and over 2 years and determine aspects of EA associated with a negative score.

METHODS

EQ-5D scores for 813 patients were longitudinally assessed over 24 months. Characteristics and health status of patients with EQ-5D < 0 were analysed. Multivariate logistic regression was used to determine aspects of EA associated with a negative score.

RESULTS

At baseline, 90 (11%) patients had a negative EQ-5D score (median EQ-5D -0.052; range -0.530 to -0.011). Almost all patients had extreme pain/discomfort and at least moderate problems in anxiety/depression domain. These patients had lower educational level, greater disease activity, higher HAQ score (greater functional disability), greater pain and fatigue, lower Short Form 36 (SF-36) mental component scores and higher CRP levels than patients with EQ-5D ≥ 0 (all P < 0.001). In the logistic regression model, worse HAQ and SF-36 mental component scores were associated with EQ-5D < 0. Results were similar at 6, 12 and 24 months, with 25, 23 and 24 patients, respectively, in a state worse than death.

CONCLUSION

Pain or discomfort, often severe, is a key domain of the EQ-5D for patients with EA in a health state worse than death, and poor HAQ and SF-36 mental component scores were always independently associated with a state worse than death. EA patients may have specific needs necessitating better management of pain and psychological state.

Quantitative benefit-risk assessment using only qualitative information on utilities

BACKGROUND

Utilities of pertinent clinical outcomes are crucial variables for assessing the benefits and risks of drugs, but numerical data on utilities may be unreliable or altogether missing. We propose a method to incorporate qualitative information into a probabilistic decision analysis framework for quantitative benefit-risk assessment.

OBJECTIVE

To investigate whether conclusive results can be obtained when the only source of discriminating information on utilities is widely agreed upon qualitative relations, for example, ''sepsis is worse than transient headache'' or ''alleviation of disease is better without than with complications.''

METHOD

We used the structure and probabilities of 3 published models that were originally evaluated based on the standard metric of quality-adjusted life years (QALYs): terfenadine versus chlorpheniramine for the treatment of allergic rhinitis, MCV4 vaccination against meningococcal disease, and alosetron for irritable bowel syndrome. For each model, we identified clinically straightforward qualitative relations among the outcomes. Using Monte Carlo simulations, the resulting utility distributions were then combined with the previously specified probabilities, and the rate of preference in terms of expected utility was determined for each alternative.

RESULTS

Our approach conclusively favored MCV4 vaccination, and it was concordant with the QALY assessments for the MCV4 and terfenadine versus chlorpheniramine case studies. For alosetron, we found a possible unfavorable benefit-risk balance for highly risk-averse patients not identified in the original analysis.

CONCLUSION

Incorporation of widely agreed upon qualitative information into quantitative benefit-risk assessment can provide for conclusive results. The methods presented should prove useful in both population and individual-level assessments, especially when numerical utility data are missing or unreliable, and constraints on time or money preclude its collection.

The way that you do it? An elaborate test of procedural invariance of TTO, using a choice-based design

The time tradeoff (TTO) method is often used to derive Quality-Adjusted Life Year health state valuations. An important problem with this method is that results have been found to be responsive to the procedure used to elicit preferences. In particular, fixing the duration in the health state to be valued and inferring the duration in full health that renders an individual indifferent, causes valuations to be higher than when the duration in full health is fixed and the duration in the health state to be valued is elicited. This paper presents a new test of procedural invariance for a broad range of time horizons, while using a choice-based design and adjusting for discounting. As one of the known problems with the conventional procedure is the violation of constant proportional tradeoffs (CPTO), we also investigate CPTO for the alternative TTO procedure. Our findings concerning procedural invariance are rather supportive for the TTO procedure. We find no violations of procedural invariance except for the shortest gauge duration. The results for CPTO are more troublesome: TTO scores depend on gauge duration, reinforcing the evidence reported when using the conventional procedure.

Constantly proving the opposite? A test of CPTO using a broad time horizon and correcting for discounting

PURPOSE

An important assumption underlying the quality-adjusted life year (QALY) model is that people trade off life years against health in the same proportion irrespective of the number of remaining life years. This is known as the constant proportional trade-offs (CPTO) condition. Previous studies have produced mixed empirical evidence about the validity of CPTO. This paper is the first to test CPTO using the time trade-off (TTO) method for a broad time horizon.

METHODS

In a sample of 83 students, we use a choice based TTO protocol to elicit TTO scores for back pain, using ten different gauge durations ranging between 1 and 46 years. The TTO scores are corrected for discounting, which is elicited by means of the direct method.

RESULTS

We find average TTO scores varying between 0.72 and 0.81. Although the scores do not differ much for different durations in absolute terms, some differences are significant, rejecting CPTO, with and without correcting for discounting. No clear relationship between TTO scores and gauge duration is found. An anchoring and rounding heuristic to some extent explains our results.

CONCLUSIONS

Our findings highlight the importance of elicitation methods and context dependencies in QALY measurement and warrant detailed investigation of their influence.

Using a discrete choice experiment to estimate health state utility values

In this study we explored a novel application of the discrete choice experiment (DCE) that resembles the time trade off (TTO) task to estimate values on the health utility scale for the EQ-5D. The DCE was tested in a survey alongside the TTO in a sample of English-speaking Canadians recruited by a market research company. The study found that the DCE is able to derive logical and consistent values for health states valued on the full health - dead scale. The DCE overcame some issues identified in the version of TTO currently used to value EQ-5D, notably allowing for fewer data exclusions and incorporating values considered worse than dead without introducing a separate valuation procedure. This has important implications for providing robust values that represent the preferences of all respondents.

Lifestyle behaviours and quality-adjusted life years in middle and older age

OBJECTIVE

to examine the relationship between combined lifestyle behaviours and quality-adjusted life years (QALYs) in a general population.

METHODS

a population-based study was conducted in 13,358 men and women who participated in the European Prospective Investigation into Cancer (EPIC)-Norfolk (baseline 1993-97). A score of 1 was given to each of non-smoking, physically not inactive, moderate alcohol consumption (1-14 units) and consumption of at least five portions of fruit and vegetables (vitamin C level ≥50 µmol/l). Short-Form Six-Dimension (SF-6D) health utility index scores were derived from the SF-36. QALYs were estimated up to follow-up (July 2007).

RESULTS

a total of 13,358 men and women were eligible to be included in the study (aged 40-79 years at baseline). A total of 12,921 people were alive at follow-up (117, 784 person-years). Mean follow-up period was ∼11.5 years. 437 (4.4% of men and 2.4% of women) died. The death rate was 6.5 times higher in people with health behaviour score 0 compared with those who scored 4 (8.4 versus 1.3%). People with higher scores had significantly higher QALYs.

CONCLUSION

our findings support the view that modifiable lifestyle factors are an important component in health improvement.

A preference-based measure of health: the VR-6D derived from the veterans RAND 12-Item Health Survey

PURPOSE

The Veterans RAND 12-Item Health Survey (VR-12) is currently the major endpoint used in the Medicare managed care outcomes measure in the Healthcare Effectiveness Data and Information Set (HEDIS(®)), referred to as the Health Outcomes Survey (HOS). The purpose of this study is to adapt the Brazier SF-6D utility measure to the VR-12 to generate a single utility index.

METHODS

We used the HOS cohorts 2 and 3 for SF-36 data and 9 for VR-12 data. We calculated SF-6D scores from the SF-36 using the algorithms developed by Brazier and colleagues. The values of the Brazier SF-6D were used to estimate utility scores from the VR-12 using a mapping approach based on a 2-stage mapping procedure, named as VR-6D.

RESULTS

The VR-6D derived from the VR-12 has similar distributional properties as the SF-6D. The change in VR-6D showed significant variations across disease groups with different levels of morbidity and mortality.

CONCLUSIONS

This study produced a utility measure for the VR-12 that is comparable to the SF-6D and responsive to change. The VR-6D can be used in evaluations of health care plans and cost-effectiveness analysis to compare the health gains that health care interventions can achieve.

Using threshold values for cost per quality-adjusted life-year gained in healthcare decisions

BACKGROUND

In many countries, the incremental cost-effectiveness ratio (ICER) is used to assess whether an intervention is worth its costs. At the same time, policy makers often feel uncomfortable with refusing reimbursement of any intervention purely on the basis of the fact that the ICER exceeds a specific threshold value. Reluctance to define a single threshold value for the ICER seems to have been stronger in social security systems than in national healthcare services systems. This study explores how basic differences between healthcare systems impact upon the potential usefulness of an ICER threshold value.

METHODS

This study is a narrative review of literature about the theoretical foundations of the ICER threshold value approach and its practical relevance in different types of healthcare systems.

RESULTS

A single ICER threshold value cannot be maintained, defined, or measured and should not be used as a policy-making tool. None of the solutions presented up until now to make the ICER threshold approach a valuable policy-making tool overcome the important weaknesses of the approach.

CONCLUSIONS

ICERs and ICER threshold values are insufficient for assessing interventions' value for money. Rather, they should be considered as one element in the decision-making process. Complete rationalization of the decision-making process by means of quantitative decision criteria is undesirable and not feasible. Increasing transparency in the criteria used for a decision and explicitness about the relative importance of each criterion should, therefore, be the major goal.

Implications of an economic model of health states worse than dead

We introduce a formal definition of health equivalent to dead into a standard model to develop previously unrecognized insights. We find that the health state viewed as equivalent to dead will depend on an individual's health prognosis, probability of survival, and rate of time preference. Our work on maximum endurable time shows that using QALY scores based on long-run preferences to value health states that last for shorter periods can alter cardinal and ordinal valuations. Simulations show that errors of substantial magnitude in QALY scores can consequently result. We describe situations where biases are likely and identify possible corrections.

On the (not so) constant proportional trade-off in TTO

Purpose

The linear and power QALY models require that people in Time Trade-off (TTO) exercises sacrifice the same proportion of lifetime to obtain a health improvement, irrespective of the absolute amount. However, evidence on these constant proportional trade-offs (CPTOs) is mixed, indicating that these versions of the QALY model do not represent preferences. Still, it may be the case that a more general version of the QALY model represents preferences. This version has the property that people want to sacrifice the same proportion of utilities of lifetime for a health improvement, irrespective of the amount of this lifetime.

Methods

We use a new method to correct TTO scores for utility of life duration and test whether decision makers trade off utility of duration and quality at the same rate irrespective of duration.

Results

We find a robust violation of CPTO for both uncorrected and corrected TTO scores. Remarkably, we find higher values for longer durations, contrary to most previous studies. This represents the only study correcting for utility of life duration to find such a violation.

Conclusions

It seems that the trade-off of life years is indeed not so constantly proportional and, therefore, that health state valuations depend on durations.

[A proposed guideline for economic evaluation of health technologies]

Over the last few years, economic evaluation of health technologies has become a major tool used by European health policy decision-makers to create strategies for prioritizing the allocation of health resources and the approval of new technologies. Spain was a pioneer in proposing the standardization of methodology applicable to economic evaluation studies. However, because health policy decision-makers refused to support the initiative, the methodology was never put into practice. In the medium term, evidence of the economic value of new health technologies financed by the national health system will probably be increasingly required. At that time, stakeholders and decision-makers will have to agree upon a clear and concise set of rules on the technical and methodological issues that must be followed by economic evaluations of health technologies. Consequently, we have provided guidelines and recommendations for producing first-rate economic evaluations. The recommendations appear under seventeen headings or sections. In each case, the recommended requirements to be satisfied by an economic evaluation of health technologies are provided and each recommendation is followed by a commentary, providing a justification and comparing and contrasting the proposal with other available alternatives.

A Markov decision process approach to temporal modulation of dose fractions in radiation therapy planning

The current state of the art in cancer treatment by radiation optimizes beam intensity spatially such that tumors receive high dose radiation whereas damage to nearby healthy tissues is minimized. It is common practice to deliver the radiation over several weeks, where the daily dose is a small constant fraction of the total planned. Such a 'fractionation schedule' is based on traditional models of radiobiological response where normal tissue cells possess the ability to repair sublethal damage done by radiation. This capability is significantly less prominent in tumors. Recent advances in quantitative functional imaging and biological markers are providing new opportunities to measure patient response to radiation over the treatment course. This opens the door for designing fractionation schedules that take into account the patient's cumulative response to radiation up to a particular treatment day in determining the fraction on that day. We propose a novel approach that, for the first time, mathematically explores the benefits of such fractionation schemes. This is achieved by building a stylistic Markov decision process (MDP) model, which incorporates some key features of the problem through intuitive choices of state and action spaces, as well as transition probability and reward functions. The structure of optimal policies for this MDP model is explored through several simple numerical examples.

Holistic preferences for 1-year health profiles describing fluctuations in health: the case of chronic obstructive pulmonary disease

BACKGROUND

There are few empirical studies on the valuation of health profiles that describe the short-term fluctuations of chronic diseases.

OBJECTIVE

This study aimed to value chronic obstructive pulmonary disease (COPD) health profiles, which describe the health of these patients over the course of 1 year from a societal perspective.

METHODS

We developed 16 COPD health profiles. Each profile combined a description of the severity of COPD during the stable phase with a description of the exacerbation profile in terms of severity, frequency and duration. These profiles were valued by a representative sample of 239 Dutch adults using the visual analogue scale (VAS) and time trade-off (TTO) methods. Value functions were estimated using random effects regression analysis.

RESULTS

Both VAS and TTO values consistently decreased as severity of the COPD profiles increased. Estimated TTO values ranged from 0.97 for mild COPD without exacerbations to 0.43 for very severe COPD with one non-serious and one serious exacerbation per year. The estimated decrements in TTO values ranged from 0.010 for having one non-serious exacerbation to 0.088 for having one non-serious plus one serious exacerbation per year.

CONCLUSIONS

The value function may be an alternative way to model the joint impact of COPD severity and exacerbations on utility values in health economic modelling studies.

A note on the nature of utility in time and health and implications for cost utility analysis

Time Trade-Off (TTO) valuations of health are widely used in economic evaluation of health care. Current approaches to eliciting TTO values, and their use in economic evaluation, rest on specific assumptions about the way utility relates to time and health. Both the assumptions themselves and evidence of violations of them are discussed in the literature - yet the issues appear not to be widely appreciated by those using and applying TTO in economic evaluation. This paper adds to that literature by demonstrating both the requirements of TTO and violations of these assumptions in terms of the underlying indifference curve maps and utility functions. The advantage of this approach is that it demonstrates very clearly a number of fundamental problems for the way TTO values are currently elicited and used in cost utility analysis. In essence, it is extremely unwise to assume that the current 'tariffs' of TTO values, such as those widely used in cost utility analysis to inform health sector decisions in many countries can be applied irrespective of the duration of the health states to which they are assigned. The estimates of QALYs that result will, quite often, simply be wrong. We conclude by pointing to a number of possible solutions.

On future non-medical costs in economic evaluations

Economic evaluation in health care is still an evolving discipline. One of the current controversies in cost-effectiveness analysis regards the inclusion or exclusion of future non-medical costs (i.e. consumption net of production) due to increased survival. This paper examines the implications of a symmetry rule stating that there should be consistency between costs included in the numerator and utility aspects included in the denominator. While the observation that no quality-adjusted life year (QALY) instruments explicitly include consumption and leisure seems to give support to the notion that future non-medical costs should be excluded when QALYs are used as the outcome measure, a better understanding of what respondents actually consider when reporting QALY weights is required. However, the more fundamental question is whether QALYs can be interpreted as utilities. Or more precisely, what are the assumptions needed for a general utility model also including consumption and leisure to be consistent with QALYs? Once those assumptions are identified, they need to be experimentally tested to see whether they are at least approximately valid. Until we have answers to these areas for future research, it seems premature to include future non-medical costs.

Feasibility and Reliability of the Annual Profile Method for Deriving QALYs for Short-Term Health Conditions

Introduction . When health varies over time, the standard quality-adjusted life year model operates under the assumptions of time utility independence within each health state and additive independence between health states. These assumptions can be relaxed by an integral assessment of disease severity over time. The authors present the annual profile method (APM), which values health profiles on a 1-year base, and test the APM for feasibility, consistency, and test-retest reliability. Methods . A population panel, general practitioners, medical advisers, and a panel of the Dutch Consumers Association valued vignettes for 46 disease stages using the visual analog scale (VAS) and time tradeoff (TTO) methods. Vignettes contained disease-specific information, a generic description (EQ-6D5L), a description of the disease course over time, and a visual representation of the disease. Feasibility was tested by missing and inconsistent responses. Consistency between and within panels was tested with a generalizability study, analysis of variance, and standard correlation coefficients. Test-retest reliability was tested with a generalizability study and intra-class correlation coefficients. Results . Missing and inconsistent responses were < 2.6 %. The valuations were consistent across panels, with generalizability coefficients of 0.78 (VAS) and 0.64 (TTO). Within the main population panel, internal consistency was satisfactory and the influence of background characteristics negligible. Test-retest reliability was high, with generalizability coefficients of 0.90 (VAS) and 0.72 (TTO). Conclusion . Feasibility and reliability of the APM for realistic health profiles are good to excellent. The APM is a promising step to bridge the gap between the quality-adjusted life year methodology and clinical reality.

On the assessment of preferences for health and duration: maximal endurable time and better than dead preferences

BACKGROUND

Several studies revealed difficulties with the valuation and analysis of health states deemed worse than dead. These problems may be linked to maximal endurable time (MET) preferences, the phenomenon that for severe states better than dead (BTD), shorter durations are often preferred to longer durations.

OBJECTIVE

To test the association between the duration of health states and their valuation.

METHODS

A representative sample of 123 Dutch respondents (age range, 18-45 years) valued 5 EQ-5D health states. With a straightforward method using BTD preferences, respondents indicated whether a state of a certain duration is better, equal to, or worse than dead. To validate these BTD preferences, MET preferences (whether a longer duration of a health state is better, equal, or worse than a shorter duration) were collected.

RESULTS

BTD and MET preferences were strongly related (P < 0.001). For severe health states, although still judged as better than dead, BTD preferences curved downwards with increasing duration. Such curved BTD patterns occurred in 28% of the respondents, especially for more severe states (P < 0.001).

CONCLUSIONS

BTD preferences revealed that the value of moderate and severe states declines with increasing duration, suggesting that health and duration interact. For states worse than dead versus states better than dead, traditional valuation techniques have the drawback that different preference questions are used. Using BTD preferences, however, a single simple preference question can assess states better than dead, as well as states worse than dead.

What difference does it make? The calculation of QALY gains from health profiles using patient and general population values

OBJECTIVES

To compare the Quality-Adjusted Life Year (QALY) values produced from a direct health profile QALY calculation method, using patient values, with those derived from a conventional QALY calculation method, using general population values.

METHODS

Comparison of QALY values generated from patient valuations of health profiles, using a chained version of the Time Trade-Off method, with QALY values derived from a conventional QALY calculation method, using general population values of EQ-5D states, an observational survey of MS patients, and a randomized controlled trial.

RESULTS

Using patient valuations of health profiles, QALY values of treatment and placebo were 2.610 and 2.568, respectively, generating a gain of 0.042. The conventional QALY method gave values of 2.042 versus 1.998, producing a gain of 0.044. These findings were generally robust under sensitivity analyses.

CONCLUSIONS

QALY values were dependent on the calculation method used, but QALY gains were similar between methods. QALY values from the conventional QALY calculation method appeared robust to most changes in the assumptions used to derive values. The direct health profile QALY method was however more able to account for heterogeneity in preferences.