Time to tweak the TTO: results from a comparison of alternative specifications of the TTO

This Dead or That Dead: Framing Effects in the Evaluation of Health States

OBJECTIVES

Current approaches to health state valuation rely on credible classification of states as either "better than dead" or "worse than dead" (WTD). We investigate how such evaluations of health states are affected by the framing in pairwise comparison tasks.

METHODS

We conducted an online survey with 361 participants to compare the propensity to evaluate a state as WTD under 6 frames: (A) using a regular time trade-off (TTO) choice task, (B) using a lead-time TTO choice task, (C) excluding the immediacy of death, (D) avoiding reference to the process of dying, (E) focusing on longevity, and (F) focusing on improvements in quality of life. Each participant evaluated 9 EQ-5D-5L health states using 3 frames. The frames were compared using several statistical approaches to confirm robustness to indirect comparisons or respondent heterogeneity and inattentiveness.

RESULTS

The odds of a state being evaluated as WTD, compared with frame A, increase 2.7-fold and 1.5-fold in frame B and E, respectively, and decrease >5-fold in frame F. Frames C and D do not differ significantly from frame A.

CONCLUSIONS

Different framings for questions about whether a state is WTD or better than dead, even if theoretically equivalent, yield substantially different results. Notably, whether a state is evaluated as WTD differs greatly between the regular TTO and lead-time TTO choice tasks and when either final outcomes or improvements over time are considered.

Comparison of Preferences and Data Quality between Discrete Choice Experiments Conducted in Online and Face-to-Face Respondents

INTRODUCTION

Discrete choice experiments (DCE) are increasingly being conducted using online panels. However, the comparability of such DCE-based preferences to traditional modes of data collection (e.g., in-person) is not well established. In this study, supervised, face-to-face DCE was compared with its unsupervised, online facsimile on face validity, respondent behavior, and modeled preferences.

METHODS

Data from face-to-face and online EQ-5D-5L health state valuation studies were compared, in which each used the same experimental design and quota sampling procedure. Respondents completed 7 binary DCE tasks comparing 2 EQ-5D-5L health states presented side by side (health states A and B). Data face validity was assessed by comparing preference patterns as a function of the severity difference between 2 health states within a task. The prevalence of potentially suspicious choice patterns (i.e., all As, all Bs, and alternating As/Bs) was compared between studies. Preference data were modeled using multinomial logit regression and compared based on dimensional contribution to overall scale and importance ranking of dimension-levels.

RESULTS

One thousand five Online respondents and 1,099 face-to-face screened (F2FS) respondents were included in the main comparison of DCE tasks. Online respondents reported more problems on all EQ-5D dimensions except for Mobility. The face validity of the data was similar between comparators. Online respondents had a greater prevalence of potentially suspicious DCE choice patterns ([Online]: 5.3% [F2FS] 2.9%, P = 0.005). When modeled, the relative contribution of each EQ-5D dimension differed between modes of administration. Online respondents weighed Mobility more importantly and Anxiety/Depression less importantly.

DISCUSSION

Although assessments of face validity were similar between Online and F2FS, modeled preferences differed. Future analyses are needed to clarify whether differences are attributable to preference or data quality variation between modes of data collection.

Time and lexicographic preferences in the valuation of EQ-5D-Y with time trade-off methodology

In the valuation of EQ-5D-Y-3L, adult respondents are asked to complete composite time trade-off (cTTO) tasks for a 10-year-old child. Earlier work has shown that cTTO utilities elicited in such a child perspective are generally higher than when adults take their own perspective. We explore how differences in time preference in child and adult perspectives could explain this effect. Furthermore, as cTTO valuation in a child perspective involves explicit consideration of immediate death for a child, we also consider how cTTO utilities could be affected by decision-makers lexicographically avoiding death in children. We report the results of an experiment in which 219 respondents valued 5 health states in both adult and child perspectives with either a standard cTTO or a lead-time TTO only approach, in which immediate death is less focal. Time preferences were measured in both perspectives. Our results suggest that utilities were lower when lead-time TTO, rather than cTTO, was used. We find large heterogeneity in time preference in both perspectives, with predominantly negative time preference. The influence of time preferences on utilities, however, was small, and correcting for time preferences did not reduce differences between utilities elicited in both perspectives. Surprisingly, we found more evidence for differences in utilities between adult and child perspectives when lead-time TTO was used. Overall, these results suggest that time and lexicographic preferences affect time trade-off valuation in child and adult perspectives, but are not the explanation for differences between these perspectives. We discuss the implications of our findings for EQ-5D-Y-3L valuation.

Time and lexicographic preferences in the valuation of EQ-5D-Y with time trade-off methodology

In the valuation of EQ-5D-Y-3L, adult respondents are asked to complete composite time trade-off (cTTO) tasks for a 10-year-old child. Earlier work has shown that cTTO utilities elicited in such a child perspective are generally higher than when adults take their own perspective. We explore how differences in time preference in child and adult perspectives could explain this effect. Furthermore, as cTTO valuation in a child perspective involves explicit consideration of immediate death for a child, we also consider how cTTO utilities could be affected by decision-makers lexicographically avoiding death in children. We report the results of an experiment in which 219 respondents valued 5 health states in both adult and child perspectives with either a standard cTTO or a lead-time TTO only approach, in which immediate death is less focal. Time preferences were measured in both perspectives. Our results suggest that utilities were lower when lead-time TTO, rather than cTTO, was used. We find large heterogeneity in time preference in both perspectives, with predominantly negative time preference. The influence of time preferences on utilities, however, was small, and correcting for time preferences did not reduce differences between utilities elicited in both perspectives. Surprisingly, we found more evidence for differences in utilities between adult and child perspectives when lead-time TTO was used. Overall, these results suggest that time and lexicographic preferences affect time trade-off valuation in child and adult perspectives, but are not the explanation for differences between these perspectives. We discuss the implications of our findings for EQ-5D-Y-3L valuation.

Valuing EQ-5D-Y: the current state of play

BACKGROUND

For nearly a decade, value sets for the EQ-5D-Y were not available, reflecting challenges in valuing child HRQoL. A methodological research programme led to publication of a valuation protocol in 2020, which was rapidly taken up by local study teams. By the end of 2022, between 11 and 17 EQ-5D-Y value sets will be available, more than for any other child HRQoL measure. It is timely to review the experience of those using the protocol to identify early learnings and remaining issues where more research is needed.

METHODS

In June 2021, the EuroQol Group organised a three-day workshop, bringing together all those involved in EQ-5D-Y value set studies and related methodological research concerning EQ-5D-Y and valuation. Workshop discussions were captured by note taking and recording all sessions and online chat. A narrative summary of all sessions was produced and synthesised to identify points of agreement and aspects of methods where uncertainty remains.

RESULTS

There was broad agreement that DCE is working well as the principal valuation method. However, the most appropriate means of anchoring the latent scale values produced by DCE remains unclear. Some studies have deviated from the protocol by extending the number of states included in TTO tasks, to better support modelling of DCE and TTO. There is ongoing discussion about the relative merits of alternative variants of TTO and other methods for anchoring. Very few studies have consulted with local end-users to gauge the acceptability of methods used to value EQ-5D-Y.

CONCLUSIONS

Priority areas for research include testing alternative methods for anchoring DCE data; exploring the preferences of adolescents; and scale differences in values for EQ-5D-Y and adult EQ-5D states, and implications of such differences for the use of EQ-5D-Y values in HTA. Given the normative elements of the protocol, engaging with HTA bodies and other local users should be the first step for all future value set studies. Value sets undertaken to date are for the three-level EQ-5D-Y. However, the issues discussed in this paper are equally relevant to valuation of the five-level version of EQ-5D-Y; indeed, similar challenges are encountered valuing any measure of child HRQoL.

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

Aim

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

Methods

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

Results

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

Discussion

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

Increasing respondent engagement in composite time trade-off tasks by imposing three minimum trade-offs to improve data quality

BACKGROUND

Web-based surveys are increasingly utilized for health valuation studies but may be more prone to lack of engagement and, therefore, poor data validity. The objective of this study was to evaluate the effect of imposed engagement (i.e., at least three trade-offs) in the composite time trade-off (cTTO) task.

METHODS

The EQ-5D-5L valuation study protocol and study design were adapted for online, unsupervised completion in two arms: base case and engagement. Validity of preferences was assessed using the prevalence of inconsistent valuations and expected patterns of TTO values. Respondent task engagement was measured using time per task. Value sets were generated using linear regression with a random intercept (RILR).

RESULTS

The base case (n = 501) and engagement arms (n = 504) clustered at different TTO values: [base case] 0, 1; [engagement] -0.5, 0.45, 0.6. Mean TTO values were lower for the engagement arm. Engagement respondents did not spend more time per TTO task: [base case] 63.3 s (SD 77.9 s); [engagement] 64.7 s (SD 73.3 s); p = 0.36. No significant difference was found between arms for prevalence of respondents with at least one inconsistent TTO value: [base case] 61.1%; [engagement] 63.5%; p = 0.43. Both value sets had significant intercepts far from 1: [base case] 0.846; [engagement] 0.783. The relative importance of the EQ-5D dimensions also differed between arms.

CONCLUSIONS

Both online arms had poor quality data. A minimum trade-off threshold did not improve engagement nor face validity of the data, indicating that modifications to the number of iterations are insufficient alone to improve data quality/validity of online TTO studies.

Comparison of online and face-to-face valuation of the EQ-5D-5L using composite time trade-off

OBJECTIVE

The aim of this study was to compare online, unsupervised and face-to-face (F2F), supervised valuation of EQ-5D-5L health states using composite time trade-off (cTTO) tasks.

METHODS

The official EuroQol experimental design and valuation protocol for the EQ-5D-5L of 86 health states were implemented in interviewer-assisted, F2F and unsupervised, online studies. Validity of preferences was assessed using prevalence of inconsistent valuations and expected patterns of TTO values. Respondent task engagement was measured using number of trade-offs and time per task. Trading patterns such as better-than-dead only was compared between modes. Value sets were generated using linear regression with a random intercept (RILR). Value set characteristics such as range of scale and dimension ranking were evaluated between modes.

RESULTS

Five hundred one online and 1,134 F2F respondents completed the surveys. Mean elicited TTO values were higher online than F2F when compared by health state severity. Compared to F2F, a larger proportion of online respondents did not assign the poorest EQ-5D-5L health state (i.e., 55555) the lowest TTO value ([Online] 41.3% [F2F] 12.2%) (p < 0.001). A higher percentage of online cTTO tasks were completed in 3 trade-offs or fewer ([Online] 15.8% [F2F] 3.7%), (p < 0.001). When modeled using the RILR, the F2F range of scale was larger than online ([Online] 0.600 [F2F] 1.307) and the respective dimension rankings differed.

CONCLUSIONS

Compared to F2F data, TTO tasks conducted online had more inconsistencies and decreased engagement, which contributed to compromised data quality. This study illustrates the challenges of conducting online valuation studies using the TTO approach.

US population norms for the EQ-5D-5L and comparison of norms from face-to-face and online samples

Purpose

Normative scores (norms) allow for comparisons between population(s) of interest and the general population, which is useful for burden of disease studies and cost-effectiveness analysis. The primary aim of this study was to estimate US visual analogue scale (EQ VAS) and utility-based norms for the EQ-5D-5L using the face-to-face sample. The secondary aim was to compare norms estimated in the face-to-face and online populations.

Methods

This study estimated population norms from two general population surveys: (a) face-to-face and (b) online. In these surveys, respondents provided their health state using the EQ-5D-5L health classifier and the EQ VAS. Descriptive statistics, including mean, standard deviation (SD), 95% confidence interval, and median for the 5L utility and EQ VAS were estimated for each sample and across relevant respondent characteristics to serve as the basis for US EQ-5D-5L norms

Results

Face-to-face sample respondents (n = 1134) were representative of the US adult general population. In this sample, mean (SD) utility decreased with increasing age until age 45 or greater (age 45–54: 0.816 (0.249) age 55–64: 0.815 (0.243) age 65–74: 0.824 (0.217) age 75 + : 0.811 (0.218)). With increasing age, more problems were reported on all dimensions except anxiety/depression; a smaller proportion of respondents age 65 and older reported problems with anxiety/depression (23.8%) as compared to the youngest respondents (42.1%). Online (n = 2018) mean utility and EQ VAS values were consistently lower than the face-to-face sample.

Conclusions

The availability of US EQ-5D-5L norms facilitates interpretation and understanding of general population and patient health.

Electronic supplementary material

The online version of this article (10.1007/s11136-020-02650-y) contains supplementary material, which is available to authorized users.

What Difference Does It Make? A Comparison of Health State Preferences Elicited From the General Population and From People With Multiple Sclerosis

BACKGROUND

A major debate in the quality-adjusted life-year (QALY) literature concerns whose preferences should be used to estimate health state values (HSVs) and to calculate QALYs.

OBJECTIVES

This study explores differences between public and patient values for multiple sclerosis (MS) health states, described using an MS-specific classification system (Multiple Sclerosis Impact Scale-8 Dimensions [MSIS-8D]).

METHODS

The MSIS-8D is an existing preference-based measure of health-related quality of life in MS, which has 2 tariffs of HSVs, based on the preferences of a representative sample of the UK general population (n = 1702) and of people with MS living in the United Kingdom (n = 1635), elicited using the time trade-off technique. Here, we explore differences between HSVs by sample type, using descriptive statistics and multivariate regression methods.

RESULTS

Overall, the survey of people with MS produced significantly higher HSVs; estimated values ranged from 0.079 to 0.883 for the general population survey and from 0.138 to 0.894 for the MS survey. Differences in HSVs were more pronounced for severe health states. The difference between patient and public values varied across the dimensions of the MSIS-8D. People with MS placed greater importance on cognition than the general population, leading to lower HSVs when impairment was at a worse level; the reverse was true for the daily activities, fatigue, and depression dimensions.

CONCLUSIONS

We identified significant differences in HSVs by sample type. Using patient rather than public values may influence the results of economic evaluations, depending on the dimensions of health-related quality of life affected by the intervention being assessed, and may therefore have important consequences for reimbursement decisions.

Valuing health states: is the MACBETH approach useful for valuing EQ-5D-3L health states?

BACKGROUND

Quality Adjusted Life Years (QALYs) are a key outcome measure widely used within health technology assessment and health service research studies. QALYs combine quantity and quality of life, with quality of life calculations relying on the value of distinct health states. Such health states' values capture the preferences of a population and have been typically built through numerical elicitation methods. Evidence points to these value scores being influenced by methods in use and individuals reporting cognitive difficulties in eliciting their preferences. Evidence from other areas has further suggested that individuals may prefer using distinct elicitation techniques and that this preference can be influenced by their numeracy. In this study we explore the use of the MACBETH (Measuring Attractiveness by a Categorical Based Evaluation Technique) non-numerical preference elicitation approach for health states' evaluation.

METHODS

A new protocol for preference elicitation based on MACBETH (only requiring qualitative judgments) was developed and tested within a web survey format. A sample of the Portuguese general population (n=243) valued 25 EQ-5D-3L health states with the MACBETH protocol and with a variant of the time trade-off (TTO) protocol, for comparison purposes and for understanding respondents' preference for distinct protocols and differences in inconsistent evaluations. Respondents answered to a short numeracy test, and basic socio-economic information collected.

RESULTS

Results show that the mean values derived from MACBETH and the TTO variant are strongly correlated; however, there are substantial differences for several health states' values. Large and similar numbers of logical inconsistencies were found in respondents' answers with both methods. Participants with higher levels of numeracy according to the test preferred expressing value judgments with MACBETH, while participants with lower levels were mostly indifferent to both methods. Higher correlations between MACBETH and TTO variant evaluations were observed for individuals with higher numeracy.

CONCLUSION

Results suggest that it is worth researching the use of non-numerical preference elicitation methods. Numeracy tests more appropriate for preference elicitation when no explicit considerations of uncertainty are made need to be explored and used. Further behavioural research is needed to fully understand the potential for using these methods in distinct settings (e.g. in different evaluation contexts and in face-to-face and non-face-to-face environments), as well as to explore the effect of literacy on assessments and on respondents' preferences.

Evaluation of Split Version and Feedback Module on the Improvement of Time Trade-Off Data

BACKGROUND

EQ-5D-5L valuation studies previously reported many inconsistent responses in time trade-off (TTO) data. A number of possible elements, including ordering effects of the valuation tasks, mistakes at the sorting question, and interviewers' (learning) effects, may contribute to their inconsistency.

OBJECTIVES

This study aimed to evaluate the effect of two modifications on consistency of TTO data in The Netherlands (NL) and Hong Kong (HK): (1) separating the valuation of the Better than Dead (BTD) and Worse than Dead (WTD) states; and (2) Implementation of feedback (FB) module by offering an opportunity to review TTO responses.

METHODS

A crossover design with two study arms was used to test the effect of the modifications. In each jurisdiction, six interviewers were involved where half the interviewers started using the standard version, and the other half started with the split version. Each version was switched after every 25 (NL) or 30 (HK) interviews until 400 interviews were completed.

RESULTS

In the NL and HK, 404 and 403 respondents participated, respectively. With the use of the FB module, the proportion of respondents with inconsistent responses was lowered from 17.8% to 10.6% (P < 0.001) in NL and from 31.8% to 22.3% (P = 0.003) in HK. The result of separating the valuation of BTD and WTD states was not straightforward because it reduced the inconsistency rate in NL but not in HK.

CONCLUSIONS

The results support implementation of the FB module to promote the consistency of the data. The separation of the BTD and WTD task is not supported.

A Computer-Assisted Personal Interview App in Research Electronic Data Capture for Administering Time Trade-off Surveys (REDCap): Development and Pretest

Background

The time trade-off (TTO) task is a method of eliciting health utility scores, which range from 0 (equivalent to death) to 1 (equivalent to perfect health). These scores numerically represent a person’s health-related quality of life. Software apps exist to administer the TTO task; however, most of these apps are poorly documented and unavailable to researchers.

Objective

To fill the void, we developed an online app to administer the TTO task for a research study that is examining general public proxy health-related quality of life estimates for persons with Alzheimer’s disease. This manuscript describes the development and pretest of the app.

Methods

We used Research Electronic Data Capture (REDCap) to build the TTO app. The app’s modular structure and REDCap’s object-oriented environment facilitated development. After the TTO app was built, we recruited a purposive sample of 11 members of the general public to pretest its functionality and ease of use.

Results

Feedback from the pretest group was positive. Minor modifications included clarity enhancements, such as rearranging some paragraph text into bullet points, labeling the app to delineate different question sections, and revising or deleting text. We also added a research question to enable the identification of respondents who know someone with Alzheimer’s disease.

Conclusions

We developed an online app to administer the TTO task. Other researchers may access and customize the app for their own research purposes.

"Naming and Framing": The Impact of Labeling on Health State Values for Multiple Sclerosis

INTRODUCTION

Health state valuation is a key input in many economic evaluations that inform resource allocation across competing healthcare interventions. Empirical evidence has shown that, in preference elicitation surveys, respondents may value a health state differently if they are aware of the condition causing it ('labeling effects'). This study investigates the impact of including a multiple sclerosis (MS) label for valuation of MS health states.

METHODS

Health state values for MS were elicited using two internet-based surveys in representative samples of the UK population ( n = 1702; n = 1788). In one survey respondents were not informed that health states were caused by MS. The second survey included a condition label for MS. Surveys were identical in all other ways. Health states were described using a MS-specific eight-dimensional classification system (MSIS-8D), and the time trade-off valuation technique was used. Differences between values for labeled and unlabeled states were assessed using descriptive statistics and multivariate regression methods.

RESULTS

Adding a MS condition label had a statistically significant effect on mean health state values, resulting in lower values for labeled MS states v. unlabeled states. The data suggest that the MS label had a more significant effect on values for less severe states, and no significant effect on values for the most severe states. The inclusion of the MS label had a differential impact across the dimensions of the MSIS-8D. Across the MSIS-8D, predicted values ranged from 0.079 to 0.883 for unlabeled states, and 0.066 to 0.861 for labeled states.

CONCLUSION

Differences reported in health state values, using labeled and unlabeled states, demonstrate that condition labels affect the results of valuation studies, and can have important implications in decision-analytic modelling and in economic evaluations.

EuroQol Protocols for Time Trade-Off Valuation of Health Outcomes

The time trade-off (TTO) valuation technique is widely used to determine utility values of health outcomes to inform quality-adjusted life-year (QALY) calculations for use in economic evaluation. Protocols for implementing TTO vary in aspects such as the trade-off framework, iteration procedure and its administration model and method, training of respondents and interviewers, and quality control of data collection. The most widely studied and utilized TTO valuation protocols are the Measurement and Valuation of Health (MVH) protocol, the Paris protocol and the EuroQol Valuation Technology (EQ-VT) protocol, all developed by members of the EuroQol Group. The MVH protocol and its successor, the Paris protocol, were developed for valuation of EQ-5D-3L health states. Both protocols were designed for a trained interviewer to elicit preferences from a respondent using the conventional TTO framework with a fixed time horizon of 10 years and an iteration procedure combining bisection and titration. Developed for valuation of EQ-5D-5L health states, the EQ-VT protocol adopted a composite TTO framework and made use of computer technology to facilitate data collection. Training and monitoring of interviewers and respondents is a pivotal component of the EQ-VT protocol. Research is underway aiming to further improve the EuroQol protocols, which form an important basis for the current practice of health technology assessment in many countries.

Dutch Tariff for the Five-Level Version of EQ-5D

BACKGROUND

In 2009, a new version of the EuroQol five-dimensional questionnaire (EQ-5D) was introduced with five rather than three answer levels per dimension. This instrument is known as the EQ-5D-5L. To make the EQ-5D-5L suitable for use in economic evaluations, societal values need to be attached to all 3125 health states.

OBJECTIVES

To derive a Dutch tariff for the EQ-5D-5L.

METHODS

Health state values were elicited during face-to-face interviews in a general population sample stratified for age, sex, and education, using composite time trade-off (cTTO) and a discrete choice experiment (DCE). Data were modeled using ordinary least squares and tobit regression (for cTTO) and a multinomial conditional logit model (for DCE). Model performance was evaluated on the basis of internal consistency, parsimony, goodness of fit, handling of left-censored values, and theoretical considerations.

RESULTS

A representative sample (N = 1003) of the Dutch population participated in the valuation study. Data of 979 and 992 respondents were included in the analysis of the cTTO and the DCE, respectively. The cTTO data were left-censored at -1. The tobit model was considered the preferred model for the tariff on the basis of its handling of the censored nature of the data, which was confirmed through comparison with the DCE data. The predicted values for the EQ-5D-5L ranged from -0.446 to 1.

CONCLUSIONS

This study established a Dutch tariff for the EQ-5D-5L on the basis of cTTO. The values represent the preferences of the Dutch population. The tariff can be used to estimate the impact of health care interventions on quality of life, for example, in context of economic evaluations.

Influenced from the start: anchoring bias in time trade-off valuations

Purpose

The de facto standard method for valuing EQ-5D health states is the time trade-off (TTO), an iterative choice procedure. The TTO requires a starting point (SP), an initial offer of time in full health which is compared to a fixed offer of time in impaired health. From the SP, the time in full health is manipulated until preferential indifference. The SP is arbitrary, but may influence respondents, an effect known as anchoring bias. The aim of the study was to explore the potential anchoring effect and its magnitude in TTO experiments.

Methods

A total of 1249 respondents valued 8 EQ-5D health states in a Web study. We used the lead time TTO (LT-TTO) which allows eliciting negative and positive values with a uniform method. Respondents were randomized to 11 different SPs. Anchoring bias was assessed using OLS regression with SP as the independent variable. In a secondary experiment, we compared two different SPs in the UK EQ-5D valuation study TTO protocol.

Results

A 1-year increase in the SP, corresponding to an increase in TTO value of 0.1, resulted in 0.02 higher recorded LT-TTO value. SP had little impact on the relative distance and ordering of the eight health states. Results were similar to the secondary experiment.

Conclusion

The anchoring effect may bias TTO values. In this Web-based valuation study, the observed anchoring effect was substantial. Further studies are needed to determine whether the effect is present in face-to-face experiments.

Estimating a Preference-Based Index for an Eight-Dimensional Health State Classification System for Multiple Sclerosis

BACKGROUND

Condition-specific measures are frequently used to assess the health-related quality of life of people with multiple sclerosis (MS). Such measures are unsuitable for use in economic evaluations that require estimates of cost per quality-adjusted life-year because they are not based on preferences.

OBJECTIVES

To report the estimation of a preference-based single index for an eight-dimensional instrument for MS, the Multiple Sclerosis Impact Scale - Eight Dimensions (MSIS-8D), derived from an MS-specific measure of health-related quality of life, the 29-item Multiple Sclerosis Impact Scale (MSIS-29).

METHODS

We elicited preferences for a sample of MSIS-8D states (n = 169) from a sample (n = 1702) of the UK general population. Preferences were elicited using the time trade-off technique via an Internet-based survey. We fitted regression models to these data to estimate values for all health states described by the MSIS-8D. Estimated values were assessed against MSIS-29 scores and values derived from generic preference-based measures in a large, representative sample of people with MS.

RESULTS

Participants reported that the time trade-off questions were easy to understand. Observed health state values ranged from 0.08 to 0.89. The best-performing model was a main effects, random effects model (mean absolute error = 0.04). Validation analyses support the performance of the MSIS-8D index: it correlated more strongly than did generic measures with MSIS-29 scores, and it discriminated effectively between subgroups of people with MS.

CONCLUSIONS

The MSIS-8D enables health state values to be estimated from the MSIS-29, adding to the methods available to assess health outcomes and to estimate quality-adjusted life-years for MS for use in health technology assessment and decision-making contexts.

The lead time tradeoff: the case of health states better than dead

BACKGROUND

Lead time tradeoff (L-TTO) is a variant of the time tradeoff (TTO). L-TTO introduces a lead period in full health before illness onset, avoiding the need to use 2 different procedures for states better and worse than dead. To estimate utilities, additive separability is assumed. We tested to what extent violations of this assumption can bias utilities estimated with L-TTO.

METHODS

A sample of 500 members of the Spanish general population evaluated 24 health states, using face-to-face interviews. A total of 188 subjects were interviewed with L-TTO and the rest with TTO. Both samples evaluated the same set of 24 health states, divided into 4 groups with 6 health states per set. Each subject evaluated 1 of the sets. A random effects regression model was fitted to our data. Only health states better than dead were included in the regression since it is in this subset where additive separability can be tested clearly.

RESULTS

Utilities were higher in L-TTO in relation to TTO (on average L-TTO adds about 0.2 points to the utility of health states), suggesting that additive separability is violated. The difference between methods increased with the severity of the health state. Thus, L-TTO adds about 0.14 points to the average utility of the less severe states, 0.23 to the intermediate states, and 0.28 points to the more severe estates.

CONCLUSIONS

L-TTO produced higher utilities than TTO. Health problems are perceived as less severe if a lead period in full health is added upfront, implying that there are interactions between disjointed time periods. The advantages of this method have to be compared with the cost of modeling the interaction between periods.

Interim EQ-5D-5L Value Set for Poland: First Crosswalk Value Set in Central and Eastern Europe

OBJECTIVE

To estimate an interim five-level EuroQol five-dimensional (EQ-5D-5L) value set for Poland on the basis of the crosswalk methodology developed by the EuroQol Group.

METHODS

On the basis of data from 3691 respondents from six European countries, the EuroQol Group has developed a method of obtaining interim value sets for the EQ-5D-5L by means of mapping to the available three-level EuroQol five-dimensional (EQ-5D-3L) value sets ("crosswalk" methodology). A significant part of the data in this study came from Polish respondents (n = 972; 26.3%). Poland is the first Central European country with EQ-5D-3L time trade-off-based social value set published. To obtain an interim EQ-5D-5L value set, we applied the crosswalk methodology to the Polish EQ-5D-3L value set.

RESULTS

Estimated Polish values for 3125 EQ-5D-5L health states are presented. Both EQ-5D-5L and EQ-5D-3L value sets have the same range (from -0.523 to 1.000), but different means (0.448 vs. 0.380) and medians (0.483 vs. 0.403), respectively. Proportionately fewer states worse than dead were observed in the EQ-5D-5L (5.4%) value set than in the EQ-5D-3L (13.2%) value set.

CONCLUSIONS

The crosswalk-based value set is available for use in EQ-5D-5L studies in Poland to calculate health state utilities. It should be considered an interim value set until values based on preferences elicited directly from a sample representative of the Polish general population become available. This study helps users of the crosswalk algorithm understand the properties of the EQ-5D-5L values generated using this method, in comparison to EQ-5D-3L values obtained with the Polish time trade-off value set. It is likely that similar results would be observed for values sets in other countries because the same crosswalk methodology applies across all countries.

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.

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.