A consistency test of the time trade-off

Research trends in contemporary health economics: a scientometric analysis on collective content of specialty journals

INTRODUCTION

Health economics is a thriving sub-discipline of economics. Applied health economics research is considered essential in the health care sector and is used extensively by public policy makers. For scholars, it is important to understand the history and status of health economics-when it emerged, the rate of research output, trending topics, and its temporal evolution-to ensure clarity and direction when formulating research questions.

METHODS

Nearly 13,000 articles were analysed, which were found in the collective publications of the ten most specialised health economic journals. We explored this literature using patterns of term co-occurrence and document co-citation.

RESULTS

The research output in this field is growing exponentially. Five main research divisions were identified: (i) macroeconomic evaluation, (ii) microeconomic evaluation, (iii) measurement and valuation of outcomes, (iv) monitoring mechanisms (evaluation), and (v) guidance and appraisal. Document co-citation analysis revealed eighteen major research streams and identified variation in the magnitude of activities in each of the streams. A recent emergence of research activities in health economics was seen in the Medicaid Expansion stream. Established research streams that continue to show high levels of activity include Child Health, Health-related Quality of Life (HRQoL) and Cost-effectiveness. Conversely, Patient Preference, Health Care Expenditure and Economic Evaluation are now past their peak of activity in specialised health economic journals. Analysis also identified several streams that emerged in the past but are no longer active.

CONCLUSIONS

Health economics is a growing field, yet there is minimal evidence of creation of new research trends. Over the past 10 years, the average rate of annual increase in internationally collaborated publications is almost double that of domestic collaborations (8.4% vs 4.9%), but most of the top scholarly collaborations remain between six countries only.

Multivariate risk preferences in the quality-adjusted life year model

The interest in multivariate and higher-order risk preferences has increased. A growing body of literature has demonstrated the relevance and impact of these preferences, but for health the evidence is lacking. We measure multivariate and higher-order risk preferences for quality of life (QoL) and longevity, the two attributes of the Quality-Adjusted Life Year (QALY) model. We observe preferences for a positive correlation between these attributes and for pooling together a fixed loss in one of the attributes and a mean-zero risk in the other, and for pooling together mean-zero risks in QoL and longevity. The findings indicate that higher-order risk preferences are stronger for health than for money. Furthermore, we test if preferences for a risky treatment for a disease affecting only QoL, depend on life expectancy. We find no such a relation, but there is a positive relation between riskiness of a comorbidity affecting life expectancy and risk aversion for a QoL treatment. We therefore observe no definitive deviation from the QALY model, although the model is more robust when expected longevity is high. Our findings suggest that the current practice of cost-effectiveness analysis should be generalized to account for risk aversion in QoL and longevity, and higher-order preferences.

An overview of the time trade-off method: concept, foundation, and the evaluation of distorting factors in putting a value on health

INTRODUCTION

Preference-based instruments measuring health status express the value of specific health states in a single number. One method used is time trade-off (TTO). Health-status values are key elements in calculating quality-adjusted life years (QALYs) and are pertinent for resource allocation. Since they are used in economic evaluations of healthcare, searching for a theoretical foundation of TTO in economics is justified.

AREA COVERED

This paper provides an overview of TTO, including its relation to economic theory, and discusses biases and distortions, compiled from recent and older research. Inconsistencies between TTO and random utility theory were detected; The TTO is confounded by time preferences and by respondents' life expectancies. TTO is cognitively challenging, therefore guidance during the interviews is needed, producing interview effects. TTO does not measure one thing at a time, nor are the values independent of other states that are being valued in the same task. That is, TTO does not exhibit theoretical measurement properties such as unidimensionality and the invariance principle.

EXPERT OPINION

We conclude that the TTO may be a pragmatic method of eliciting health state values, but the limitations in regard to measurement theory and practical elicitation problems makes it prone to inconsistencies and arbitrariness.

New findings from the time trade-off for income approach to elicit willingness to pay for a quality adjusted life year

In this paper we empirically investigate how to appropriately model utility of wealth and health. We use a recently proposed alternative approach to value willingness to pay (WTP) for health, making use of trade-offs between income and life years or quality of life, which we extend to allow for a more realistic multiplicative utility function over health and money. Moreover, we show how reference-dependency can be incorporated into this model and derive its predictions for WTP elicitation. We propose three experimental elicitation procedures and test these in a feasibility study, analysing the responses under different assumptions about the discount rate. Several interesting results are reported: first, the data are highly skewed, but if we trim the 5% lowest and highest values, we obtain plausible WTP estimates. Second, the results differ considerably between procedures, indicating that WTP estimates are sensitive to the assumed utility function. Third, respondents appear to be loss averse for both health and money, which is consistent with assumptions from prospect theory. Finally, our results also indicate that respondents are more willing to trade quality of life than life years.

Health utilities for chronic low back pain

BACKGROUND

Chronic low back pain (LBP) is a common health problem, with a large potential for primary prevention. Health utilities (HU) reflect which proportion of their expected remaining life time individuals would hypothetically trade to be alleviated of a health condition of interest. A value of 0 means "prefer to die immediately", a value of 1 means "not willing to trade any life time". The aim of this cross-sectional study was to assess HU for LBP patients and for healthy participants and to examine whether HU for LBP are useful indicators to substantiate preventive and therapeutic decision making.

METHODS

Healthy participants (n = 126) and LBP patients (n = 32) were recruited mainly among the employees of a tertiary care hospital in Germany. Standardized LBP scenarios were presented to all participants and HU values were assessed using the time-trade-off method.

RESULTS

Median HU for LBP were 0.90 (IQR 0.31) for participants and 0.93 (IQR 0.10) for LBP patients. Measurements were consistent across illness severity ratings with HU and with a visual analogue scale (VAS); in the healthy sample the intraclass correlation coefficient (ICC) was 0.61 (95% CI 0.23-1.00, F(1125) = 190, p < .001), in the patient sample the ICC was 0.66 (95% CI = 0.24-1.00, F(1,31) = 62, p < .001). 8% of participants reported HU of 1. There was no statistically significant relation between HU and age, income, or gender.

CONCLUSION

On average, participants chose a 7 to 10% shorter life expectancy to avoid LBP, but almost 1 in 10 participants were not willing to trade any life years. The results indicate a certain stability of HU due to the comparability of HU ratings across patients and healthy participants, the measurement consistency when comparing VAS and HU ratings, and the lack of association between demographic variables and HU. This underlines the usefulness of HU for measuring illness severity in comparative health economics evaluations of preventive and therapeutic measures that address chronic LBP or other pain-characterized diseases. Future studies should focus on different LBP intensities and derive stratified HU that reflect the distribution of pain intensity in the population.

Exploring a new method for deriving the monetary value of a QALY

Several studies have sought to determine the monetary value of health gains expressed as quality adjusted life years (QALYs) gained, predominantly using willingness to pay approaches. However, willingness to pay has a number of recognized problems, most notably its insensitivity to scope. This paper presents an alternative approach to estimate the monetary value of a QALY, which is based on the time trade-off method. Moreover, it presents the results of an online study conducted in the Netherlands exploring the feasibility of this novel approach. The results seem promising, but also highlight a number of methodological problems with this approach, most notably nontrading and the elicitation of negative values. Additional research is necessary to try to overcome these problems and to determine the potential of this new approach.

Correcting Biases in Standard Gamble and Time Tradeoff Utilities

The standard gamble (SG) method and the time tradeoff (TTO) method are commonly used tomeasure utilities. However, they are distorted by biases due to loss aversion, scale compatibility, utility curvature for life duration, and probability weighting. This article applies corrections for these biases and provides new data on these biases and their corrections. The SG and TTO utilities of 6 rheumatoid arthritis health states were assessed for 45 healthy respondents. Various corrections of utilities were considered. The uncorrected TTO scores and the corrected (for utility curvature) TTO scores provided similar results. This article provides arguments suggesting that the TTO scores are biased upward rather than having balanced biases. The only downward bias in TTO scores was small and probably cannot offset the upward biases. TheTTOscores are higher than the theoretically most preferred correction of the SG, the mixed correction. These findings suggest that uncorrected SG scores, which are higher than TTO scores, are too high.

An elicitation of utility for quality of life under prospect theory

This paper performs several tests of decision analysis applied to the health domain. First, we conduct a test of the normative expected utility theory. Second, we investigate the possibility to elicit the more general prospect theory. We observe risk aversion for gains and losses and violations of expected utility. These results imply that mechanisms governing decisions in the health domain are similar to those in the monetary domain. However, we also report one important deviation: utility is universally concave for the health outcomes used in this study, in contrast to the commonly found S-shaped utility for monetary outcomes, with concave utility for gains and convex utility for losses.

Are people consistent when trading time for health?

The conventional, or standard, time trade-off (TTO) procedure, which is used to elicit the values that people place on health states that are in turn required to calculate quality adjusted life-years (QALYs), asks respondents to trade off fewer life years for better health. It is possible to reverse the procedure to ask respondents to trade off less health for more life years. Theoretically, these two procedures should generate the same TTO values for any given health state. This article reports that for health states defined by differing frequencies of migraine attack, the standard TTO gives health state values that are significantly higher than those given by the reverse TTO. The observed systematic procedural invariance, which substantiates some previous findings reported in the literature and is consistent with a loss aversion effect, challenges the validity of the TTO for generating reliable valuations of health states.

Quantifying Long-Term Care Preferences

Background. Current policies redirecting long-term care (LTC) delivery away from institutional care to home- and community-based services are being made in the absence of crucial evidence on preferences. Studies indicate that the shift to home care is generally not cost-saving; thus, an empirical assessment of effectiveness is needed to evaluate policies incenting home care investment. This study quantifies LTC preferences between different delivery modes. Design. This study extended the time tradeoff method to elicit utilities and LTC preferences associated with the receipt of different modes of LTC services, conditional on health states defined by varying levels of functional and cognitive impairment. Users’ LTC preferences are measured as differential utilities between alternative LTC options for each health state. Results. For the same health state, respondents ( n = 81) significantly preferred home care over institutional care, except for the most impaired health state. The preference for home care over institutional care is quantified as 0.30 quality-of-life (QOL) weight when people need help with only 1 activity of daily living (ADL). The preference for home care depends significantly on levels of disability and was weaker once the need for help became greater. Under the most severe health state of having moderate to severe dementia and needing help with 6 ADLs, the quantified home care preference was only 0.03 QOL weight and was not statistically significant. Limitations. Because the sample is mostly composed of African Americans, the results may not be generalizable to other racial and ethnic groups. Conclusions. People do not always strongly prefer home care over institutional care, as is often assumed. The costs of expanding home- and community-based care should be weighed against these preferences.

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.

Utility elicitation study in the UK general public for late-stage chronic lymphocytic leukaemia

OBJECTIVES

In the United Kingdom (UK), chronic lymphocytic leukaemia (CLL) makes up 40 % of all leukaemias in patients over 65 years. The study objective was to obtain societal preferences in the UK for "progression-free" and "progressive" states of late-stage CLL, refractory to current first and second line regimens. Preferences were also obtained for selected treatment-related adverse events (AEs).

METHODS

A utility elicitation study, using the time trade-off (TTO) method, was conducted by face-to-face interviews with 110 subjects for a baseline disease state (before treatment), three primary disease states [progression-free survival (PFS) and treatment responder, PFS and treatment non-responder and disease progression], and 4 AE sub-states (PFS responder with thrombocytopenia, neutropenia, and infection, and PFS non-responder with infection). TTO scores were converted into utility values, and disutilities were calculated for AEs. Visual analogue scale (VAS) scores were obtained.

RESULTS

The primary disease state mean TTO utility scores were: baseline: 0.549; PFS response: 0.671; PFS non-response: 0.394; and progression: 0.214. The mean TTO utility (disutility) scores for the AEs were: PFS response with thrombocytopenia, 0.563 (-0.108), neutropenia, 0.508 (-0.163), and infection, 0.476 (-0.195); PFS non-response with infection, 0.333 (-0.061). The VAS results were in line with the TTO results.

CONCLUSIONS

The utility was higher for the PFS state than baseline, but decreased below baseline in non-response and disease progression states. AEs had an impact on utility within the PFS response state. The severe infection AE had a greater impact on utilities for the responding to treatment state compared to the non-responder state.

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.

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.

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.

Elicitation of health state utilities associated with differing durations of morning stiffness in rheumatoid arthritis

OBJECTIVE

Specific symptoms of rheumatoid arthritis (RA), including joint stiffness and functional disability, are most severe in the morning. 'Morning stiffness' has a negative impact on health-related quality-of-life (HRQoL); however, how HRQoL is correlated to morning stiffness duration is unknown. The objective of this study was to obtain population-based utility values associated with different durations of morning stiffness in RA.

DESIGN AND METHODS

The time-trade-off (TTO) approach was used to elicit utility values for four different health states (HS), which differed in morning stiffness duration. One hundred and nine members of the UK general public rated each HS in individual face-to-face interviews with trained investigators. TTO scores were converted into utility values. Visual Analog Scale (VAS) scores were obtained to validate TTO scores.

RESULTS

On a scale of 0 (death) to 1 (full health), a mean utility value of 0.45±0.29 was elicited for ∼3 h of morning stiffness (anchor HS), 0.50±0.28 for 2-3 h of morning stiffness (HS1), 0.61±0.25 for 1-2 h of morning stiffness (HS2) and 0.78±0.20 for <1 h of morning stiffness (HS3). The difference between each HS was statistically significant (p<0.01). Mean VAS utility scores followed the same trend. Utility incrementally increased with each HS associated with a shorter duration of morning stiffness. Limitations of this research include potential bias from the TTO method due to the discounting effect of time, scale compatibility, and loss aversion.

CONCLUSIONS

The UK population-based utility values show a reduction in morning stiffness duration in RA is associated with improved HRQoL. Despite the impact of morning stiffness on HRQoL, it is rarely evaluated and little is known as to how it is affected by current treatments. The results of this study can be applied in future cost-utility analyses of healthcare interventions which target an improvement in morning stiffness duration for RA patients.

A test of independence of discounting from quality of life

The quality-adjusted life-years (QALY) model assumes quality and quantity of life can be multiplied into a single index and requires quality and quantity to be mutually independent, which need not hold empirically. This paper proposes a new test for measuring independence of utility of life duration from quality of life in a riskless setting. We use a large representative sample of Dutch citizens and include two health states generally considered better than dead (BTD) and one health state considered worse than dead (WTD). Independence cannot be rejected when comparing the BTD health states, but is rejected when comparing the BTD states with the WTD state. In particular, utility of life duration becomes more concave for the WTD state. This may suggest that independence holds only for BTD health states. This has implications for the QALY model and would require using sign-dependent utility of life duration functions.

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.

Comparison of one and two-stage revision of total hip arthroplasty complicated by infection: a Markov expected-utility decision analysis

BACKGROUND

Two-stage revisions of total hip arthroplasties complicated by chronic infection result in reinfection rates that are lower than those following single-stage revisions but may also result in increased surgical morbidity. Using a decision analysis, we compared single-stage and two-stage revisions to determine which treatment modality resulted in greater quality-adjusted life years (QALYs).

METHODS

A review of the literature on the treatment of patients with an infection at the site of a total hip arthroplasty provided probabilities; utility values for common postoperative health states were determined in a previously published study. With these data, we conducted a Markov cohort simulation decision analysis. Sensitivity analysis validated the model, and comparisons were made in terms of QALYs.

RESULTS

The twelve-month model favored direct-exchange revision over the two-stage approach, regardless of whether surgeon or patient-derived utilities were used (0.945 versus 0.896 and 0.897 versus 0.861 QALYs for the patient and surgeon models, respectively). Similar results were observed in a lifetime model with a ten-year life expectancy (7.853 versus 7.771, and 7.438 versus 7.362 QALYs, respectively). The findings were found to be robust in sensitivity analyses in which clinically relevant ranges of input variables were used.

CONCLUSIONS

This analysis favored the direct-exchange arthroplasty over the two-stage approach. This study should be considered hypothesis-generating for future randomized controlled trials in which, ideally, health end points will be considered in addition to the eradication of infection.

The value of correcting values: influence and importance of correcting TTO scores for time preference

OBJECTIVES

Quality-adjusted life year (QALY) values measured by means of the time tradeoff (TTO) method are often used in economic evaluations. However, these values are mostly not corrected for time preference, i.e., a lower valuation being attached to later life years than to earlier life years, and therefore may underestimate the true QALY weights. Moreover, the magnitude of the underestimation depends on the severity of the health state and the horizon chosen in the TTO method. Hence, we cannot just add a constant component to all existing QALY tariffs. In this study, we estimated the value of correcting TTO scores. We showed the possible consequences for health policymaking when we correct TTO scores for time preference, thereby taking into account severity and horizon.

METHODS

We employed the results obtained using a nonparametric time preference elicitation method. We made use of experimental time preference data, in order to better represent individuals' time preferences.

RESULTS

Our results demonstrate that correcting for time preference does not result in one clear influence on the QALY gains from health changes. When considering these changes in the context of cost-utility ratios, the proportional change in the QALY gain is crucial.

CONCLUSIONS

Correcting TTO scores has a moderate, yet nonnegligible influence on outcomes. We conclude that correcting TTO scores for time preference is feasible and influential, so that there can be a substantial value of correcting values for time preference.

A prospective cohort study defining utilities using time trade-offs and the Euroqol-5D to assess the impact of cancer-related lymphedema

BACKGROUND

The devastating impact of lymphedema on cancer survivors' quality of life has prompted consideration of several changes in medical and surgical care. Unfortunately, our understanding of the benefits gained from these approaches relative to their cost remains limited. This study was designed to estimate utilities for lymphedema and characterize how utilities differ between subgroups defined by lymphedema etiology and distribution.

METHODS

A consecutive sample of 236 subjects with lymphedema seen at a lymphedema clinic completed both a time trade-off (TTO) exercise and the Euroqol 5D. Responses were adjusted in multivariate regression models for demographic factors, comorbidities, and lymphedema severity/location.

RESULTS

Most participants (167 of 236, 71%) had lymphedema as a consequence of cancer treatment; 123 with breast cancer and upper extremity involvement. Mean TTO utility estimates were consistently higher than Euroqol 5D estimates. Unadjusted TTO (0.85; standard deviation [SD], 0.21) and Euroqol 5D (0.76; SD, 0.18) scores diminished with increasing lymphedema stage and patient body mass index (BMI). Adjusted utility scores were lowest in patients with cancer-related lower extremity lymphedema (TTO=0.82; SD, 0.04 and Euroqol 5D=0.80; SD, 0.03). Breast cancer patients also had lower adjusted Euroqol 5D scores (0.80; SD, 0.02).

CONCLUSIONS

Lymphedema-associated utilities are in the range of 0.80. Lower utilities are observed for patients with higher lymphedema stages, elevated BMI, and cancer-related lymphedema. Greater expenditures for the prevention and treatment of cancer-related lymphedema are warranted.

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 comparison of preferences for two GLP-1 products--liraglutide and exenatide--for the treatment of type 2 diabetes

OBJECTIVE

To use time trade-off (TTO) to compare patient preferences for profiles of two glucagon-like peptide (GLP-1) products for the treatment of type 2 diabetes (liraglutide and exenatide) that vary on four key attributes - efficacy (as measured by hemoglobin A(1C)), incidence of nausea, incidence of hypoglycemia, and dosing frequency (QD vs. BID) - and measure the contribution of those attributes to preferences.

METHODS

A total of 382 people with T2DM were recruited to participate in an internet-based survey consisting of a series of health-related questions, a conjoint exercise and a set of time trade-off items. In the conjoint exercise, respondents were presented with eight pairs of hypothetical GLP-1 profiles, and completed a time-tradeoff exercise for each pair.

RESULTS

The product profile representing liraglutide was preferred by 96% of respondents and resulted in significantly higher health utilities (0.038) than the product profile representing exenatide (0.978 vs. 0.94, p < 0.05). Estimated preference scores from the conjoint analysis revealed that efficacy measured by hemoglobin A(1C) is the most important attribute, followed by nausea, hypoglycemia, and dosing schedule.

LIMITATIONS

On-line participants may not represent 'typical' type 2 diabetes patients, and brief product profiles represented results from clinical trials, not clinical practice

CONCLUSION

Based on the four attributes presented, patients prefer liraglutide over exenatide. Preference is based on superior efficacy and less nausea more than less hypoglycemia and once-daily dosing.

International comparisons in valuing EQ-5D health states: a review and analysis

OBJECTIVE

To identify the key methodological issues in the construction of population-level EuroQol 5-dimensions (EQ-5D)/time trade-off (TTO) preference elicitation studies.

METHOD

This study involved three components. The first was to identify existing population-level EQ-5D TTO studies. The second was to illustrate and discuss the key areas of divergence between studies, including the international comparison of tariffs. The third was to portray the relative merits of each of the approaches and to compare the results of studies across countries.

RESULTS

While most articles report use of the protocol developed in the original UK study, we identified three key areas of divergence in the construction and analysis of surveys. These are the number of health states valued to determine the algorithm for estimating all health states, the approach to valuing states worse than immediate death, and the choice of algorithm. The evidence on international comparisons suggests differences between countries although it is difficult to disentangle differences in cultural attitudes with random error and differences as a result of methodological divergence.

CONCLUSIONS

Differences in methods may obscure true differences in values between countries. Nevertheless, population-specific valuation sets for countries engaging in economic evaluation would better reflect cultural differences and are therefore more likely to accurately represent societal attitudes.

A comparison of physician and patient time trade-offs for postoperative hip outcomes

OBJECTIVE

To elicit infected hip arthroplasty preferences from outpatients and surgeons using time trade-off method based on a paper-based survey.

METHODS

Outpatients were included if they were 20 to 80 years of age, did not have a history of hip pain or surgery, and did not have a diagnosis of dementia. Orthopedic surgeons were high-volume joint replacement specialists or who performed >or=50 joint replacements per year. Preference measures were elicited using trade-offs between impaired health versus full health with shortened life, and between two temporary health states.

RESULTS

Patient preference scores were in some cases higher than surgeon preference scores. The difference was most pronounced for the health state constant severe pain. Outpatients revealed much higher preferences for staying in short-term major medical complication as compared with surgeons.

CONCLUSIONS

Preference measures derived in this study can be used in decision-making for complications related to hip surgeries.

The duration effect: a link between TTO and VAS values

The value of a health state may depend on how long an individual has had to endure the health state (i.e. hedonic load). In this paper, we test the constant proportionality (CP) assumption and determine the sign of relationship between duration and health state value for 42 health states using the nationally representative data from the United Kingdom Measurement and Valuation of Health study. The results reject the CP assumption and suggest that the relationship is negative for optimal health (i.e. fair innings argument) and that the relationship is positive for poorer health states (i.e. adaptation). We find no evidence of the maximum endurable time hypothesis using these data. This evidence on the duration effect has important implications for outcomes research and the economic evaluation of interventions.

The correction of TTO-scores for utility curvature using a risk-free utility elicitation method

This paper describes and employs a new method to correct time tradeoff (TTO)-scores for utility of life duration curvature. In contrast to most previous attempts to do so, it uses a risk-free method that corresponds well to the risk-free properties of the TTO-method. In addition, the method is robust to several biases that occur under methods that incorporate risk. Our results show a significant degree of curvature in utility of life duration and therefore a clear bias in TTO-scores. The risk-free method seems to be useful to correct TTO-scores for this influence and leads to significantly higher quality-adjustment factors.

Can we fix it? Yes we can! But what? A new test of procedural invariance in TTO-measurement

The TTO-method is often used to value health states, but it is susceptible to several biases and methodological difficulties. One of these is a violation of procedural invariance, which means that the way a TTO-question is framed, i.e. either by fixing the period in imperfect health or that in perfect health, can have a substantial effect on the elicited value of a health state. There are four important sources of discrepancy of the two procedures: loss aversion, maximum endurable time, scale compatibility and discounting. In this article, we present the results of a new test of procedural invariance in which we avoided or corrected for two of these sources (discounting and maximum endurable time). Our results indicate that while correcting for discounting does diminish the difference between the two TTO-procedures, a large and significant violation of procedural invariance remains. Loss aversion is probably the main determinant of the remainder of this difference.

Health state utilities: a framework for studying the gap between the imagined and the real

OBJECTIVES

Health state utilities play an important role in decision analysis and cost-utility analysis. The question whose utilities to use at various levels of health-care decision-making has been subject of considerable debate. The observation that patients often value their own health, but also other health states, higher than members of the general public raises the question what underlies such differences? Is it an artifact of the valuation methods? Is it adaptation versus poor anticipated adaptation? This article describes a framework for the understanding and study of potential mechanisms that play a role in health state valuation. It aims at connecting research from within different fields so that cross-fertilization of ideas may occur.

METHODS

The framework is based on stimulus response models from social judgment theory. For each phase, from stimulus, through information interpretation and integration, to judgment, and, finally, to response, we provide evidence of factors and processes that may lead to different utilities in patients and healthy subjects.

RESULTS

Examples of factors and processes described are the lack of scope of scenarios in the stimulus phase, and appraisal processes and framing effects in the information interpretation phase. Factors that play a role in the judgment phase are, for example, heuristics and biases, adaptation, and comparison processes. Some mechanisms related to the response phase are end aversion bias, probability distortion, and noncompensatory decision-making.

CONCLUSIONS

The framework serves to explain many of the differences in valuations between respondent groups. We discuss some of the findings as they relate to the field of response shift research. We propose issues for discussion in the field, and suggestions for improvement of the process of utility assessment.

Decision analysis of medical and surgical treatments for trigeminal neuralgia: How patient evaluations of benefits and risks affect the utility of treatment decisions

Trigeminal neuralgia (TN) is a rare form of neuropathic facial pain characterised by severe, paroxysmal pains in the face. Little is known about the decision process in treatment of TN, and management with anti-epileptic drugs or surgical procedures carries risks of side effects, recurrence and complications. One hundred fifty-six previously diagnosed TN patients completed an adapted time-trade-off utility measurement questionnaire to ascertain how they valued the potential outcomes from various surgical and medical treatments. The decision analysis revealed that microvascular decompression surgery (MVD) offered the best chance of improved quality of life or highest maximum expected utility (MEU). MVD (MEU=16.08 out of a possible 20) was closely followed by balloon compression (MEU=15.97), percutaneous glycerol rhizolysis (MEU=15.61) and then radiofrequency thermocoagulation (MEU=14.93). Medication offered the least optimal chance of improved quality of life (MEU=14.61). The difference between the highest (MVD) and lowest scoring treatments (medication) was 7.3% (1.46/20). These results were sensitive to some utility values, meaning the preferred treatment is changed by the values patients assign to outcomes. As surgical techniques narrowly offer the highest chance of maximising patient quality of life, all patients with TN should consider surgery. However, surgery is not right for everyone, and patients should be informed about their full range of choices. Treatment decisions must take place after careful consideration of the values patients place on benefits and risks of treatment.

Utilities and disutilities for type 2 diabetes treatment-related attributes

INTRODUCTION

Although cost-utility analyses are frequently used to estimate treatment outcomes for type 2 diabetes, utilities are not available for key medication-related attributes. The purpose of this study was to identify the utility or disutility of diabetes medication-related attributes (weight change, gastrointestinal side effects, fear of hypoglycemia) that may influence patient preference.

METHODS

Patients with type 2 diabetes in Scotland and England completed standard gamble (SG) interviews to assess utility of hypothetical health states and their own current health state. The EQ-5D, PGWB, and Appraisal of Diabetes Symptoms were administered. Construct validity and differences among health states were examined with correlations, t-tests, and ANOVAs.

RESULTS

A total of 129 patients (51 Scotland; 78 England) completed interviews. Mean utility of diabetes without complications was 0.89. Greater body weight was associated with disutility, and lower body weight with added utility (e.g., 3% higher = -0.04; 3% lower = +0.02). Gastrointestinal side effects and fear of hypoglycemia were associated with significant disutility (p < 0.001). SG utility of current health (mean = 0.87) demonstrated construct validity through correlations with patient-reported outcome measures (r = 0.08-0.31).

DISCUSSION

The vignette-based approach was feasible and useful for assessing added utility or disutility of medication-related attributes.

Recombinant erythropoietin for chemotherapy-related anaemia: economic value and health-related quality-of-life assessment using direct utility elicitation and discrete choice experiment methods

OBJECTIVE

To assess both the health-related quality of life (HR-QOL) and the economic value of erythropoietin treatment in chemotherapy-related anaemia using direct utility elicitation and discrete choice experiment (DCE) methods from a societal perspective in the UK.

METHODS

The time trade-off (TTO) method was employed to obtain utility values suitable for the calculation of QALYs for no, mild, moderate and severe anaemia. Health-state descriptions were developed using the Functional Assessment of Cancer Therapy - Anaemia (FACT-AN) subscale and the EQ-5D questionnaires, and were validated by clinical experts and patients. In addition, a DCE was implemented to elicit preferences for various anaemia treatment scenarios. The DCE analysis comprised important aspects of treatment identified from a literature review and by consultation with expert clinicians and cancer patients. The DCE included cost as an attribute in order to elicit willingness-to-pay (WTP) values (pound, 2004 values). The two methods were applied in the same cross-sectional sample of 110 lay people. Face-to-face interviews were conducted between February and March 2004.

RESULTS

The mean utility scores were 0.86 (standard error [SE] 0.014) for the no-anaemia state, and 0.78 (SE 0.016), 0.61 (SE 0.020) and 0.48 (SE 0.020) for the mild, moderate and severe anaemia states, respectively. The DCE results revealed the following preferences as significant predictors of choice: higher level of relief from fatigue, lower duration of administration, subcutaneous/intravenous administration versus cannula injection, GP versus hospital location, lower risk of infection or allergic reactions and lower cost per month to the patient. Attribute levels were valued higher for recombinant erythropoietin than for blood transfusion; this is reflected in an incremental welfare value of 368 pounds (95% CI 318, 419).

CONCLUSIONS

The results highlight a societal view that the severity of chemotherapy-related anaemia will significantly affect cancer patients' HR-QOL. The DCE survey shows that the public value favourably the attributes of treatment with recombinant erythropoietin, and indicates a likely patient preference for treatment with recombinant erythropoietin over blood transfusion.

A theoretical framework for TTO valuations of health

This paper proposes a theoretical framework, drawing on Hicks utility theory, for the Time Trade-off (TTO) method conventionally used to value health states. We briefly describe that theory and posit four distinctive TTO valuation approaches suggested by it: each of compensating variation and equivalent variation for both gains and losses in health, with valuation of health states in each case derived from trade-offs between health and length of life. Recent developments and research on TTO valuation are placed in the context of this framework.

Towards a better QALY model

This paper presents a test of the predictive validity of various classes of QALY models (i.e. linear, power and exponential models). We first estimated TTO utilities for 43 EQ-5D chronic health states and next these states were embedded in nonchronic health profiles. The chronic TTO utilities were then used to predict the responses to TTO questions with nonchronic health profiles. We find that the power QALY model clearly outperforms linear and exponential QALY models. Optimal power coefficient is 0.65. Our results suggest that TTO-based QALY calculations may be biased. This bias can be corrected using a power QALY model.

Trading people versus trading time: what is the difference?

Background

Person trade-off (PTO) elicitations yield different values than standard utility measures, such as time trade-off (TTO) elicitations. Some people believe this difference arises because the PTO captures the importance of distributive principles other than maximizing treatment benefits. We conducted a qualitative study to determine whether people mention considerations related to distributive principles other than QALY-maximization more often in PTO elicitations than in TTO elicitations and whether this could account for the empirical differences.

Methods

64 members of the general public were randomized to one of three different face-to-face interviews, thinking aloud as they responded to TTO and PTO elicitations. Participants responded to a TTO followed by a PTO elicitation within contexts that compared either: 1) two life-saving treatments; 2) two cure treatments; or 3) a life-saving treatment versus a cure treatment.

Results

When people were asked to choose between life-saving treatments, non-maximizing principles were more common with the PTO than the TTO task. Only 5% of participants considered non-maximizing principles as they responded to the TTO elicitation compared to 68% of participants who did so when responding to the PTO elicitation. Non-maximizing principles that emerged included importance of equality of life and a desire to avoid discrimination. However, these principles were less common in the other two contexts. Regardless of context, though, participants were significantly more likely to respond from a societal perspective with the PTO compared to the TTO elicitation.

Conclusion

When lives are at stake, within the context of a PTO elicitation, people are more likely to consider non-maximizing principles, including the importance of equal access to a life-saving treatment, avoiding prejudice or discrimination, and in rare cases giving treatment priority based purely on the position of being worse-off.

A test of prospect theory

Objectives: Prospect theory (PT) hypothesizes that people judge states relative to a reference point, usually assumed to be their current health. States better than the reference point are valued on a concave portion of the utility function; worse states are valued on a convex portion. Using prospectively collected utility scores, the objective is to test empirically implications of PT.

Methods: Osteoarthritis (OA) patients undergoing total hip arthroplasty periodically provided standard gamble scores for three OA hypothetical states describing mild, moderate, and severe OA as well as their subjectively defined current state (SDCS). Our hypothesis was that most patients improved between the pre- and postsurgery assessments. According to PT, scores for hypothetical states previously > SDCS but now < SDCS should be lower at the postsurgery assessment.

Results: Fourteen patients met the criteria for testing the hypothesis. Predictions were confirmed for 0 patients; there was no change or mixed results for 6 patients (42.9 percent); and scores moved in the direction opposite to that predicted by PT for 8 patients (57.1 percent).

Conclusions: In general, the direction and magnitude of the changes in hypothetical-state scores do not conform to the predictions of PT.