Time Trade-off Values Research Articles

Cost-Effectiveness of Femtosecond Laser-Assisted Cataract Surgery versus Phacoemulsification Cataract Surgery

To perform a comparative cost-effectiveness analysis (CEA) of femtosecond laser-assisted cataract surgery (LCS) and conventional phacoemulsification cataract surgery (PCS) DESIGN: Retrospective CEA using computer-based econometric modeling. Hypothetical cohort of patients undergoing cataract surgery in the better eye based on a review of the current literature and our direct experience using LCS. A cost-effectiveness decision tree model was constructed to analyze the cost-effectiveness of LCS compared with PCS. Complication rates of cataract surgery were obtained from a review of the current literature to complete the cohort of patients and outcomes. This data was incorporated with time trade-off utility values converted from visual acuity outcomes. Improvements in best-corrected visual acuity obtained from the literature were used to calculate the increase in quality-adjusted life-years (QALYs) in a hypothetical cohort between 6 months and 1 year after cataract surgery. This was combined with approximate costs in a cost-utility analysis model to determine the incremental cost-effectiveness ratios (ICERs). Based on the simulated complication rates of PCS and LCS and assuming resultant visual acuity outcome improvement of 5% in uncomplicated cases of LCS, the cost-effectiveness (dollars spent per QALY) gained from LCS was not cost-effective at $92 862 Australian Dollars. The total QALY gain for LCS over PCS was 0.06 units. Multivariate sensitivity analyses revealed that LCS would need to significantly improve visual outcomes and complications rates over PCS, along with a reduction in cost to patient, to improve cost effectiveness. Modeling a best-case scenario of LCS with excellent visual outcomes (100%), a significant reduction in complications (0%) and a significantly reduced cost to patient (of $300) resulted in an ICER of $20 000. Laser cataract surgery, irrespective of potential improvements in visual acuity outcomes and complication rates, is not cost effective at its current cost to patient when compared with cost-effectiveness benchmarks and other medical interventions, including PCS. A significant reduction in the cost to patient (via reduced consumable/click cost) would increase the likelihood of LCS being considered cost effective.

Swedish experience-based value sets for EQ-5D health states

PurposeTo estimate Swedish experience-based value sets for EQ-5D health states using general population health survey data.MethodsApproximately 45,000 individuals valued their current health status by means of time trade off (TTO) and visual analogue scale (VAS) methods and answered the EQ-5D questionnaire, making it possible to model the association between the experience-based TTO and VAS values and the EQ-5D dimensions and severity levels. The association between TTO and VAS values and the different severity levels of respondents’ answers on a self-rated health (SRH) question was assessed.ResultsAlmost all dimensions (except usual activity) and severity levels had less impact on TTO valuations compared with the UK study based on hypothetical values. Anxiety/depression had the greatest impact on both TTO and VAS values. TTO and VAS values were consistently related to SRH. The inclusion of age, sex, education and socioeconomic group affected the main effect coefficients and the explanatory power modestly.ConclusionsA value set for EQ-5D health states based on Swedish valuations has been lacking. Several authors have recently advocated the normative standpoint of using experience-based values. Guidelines of economic evaluation for reimbursement decisions in Sweden recommend the use of experience-based values for QALY calculations. Our results that anxiety/depression had the greatest impact on both TTO and VAS values underline the importance of mental health for individuals’ overall HRQoL. Using population surveys is in line with recent thinking on valuing health states and could reduce some of the focusing effects potentially appearing in hypothetical valuation studies. Electronic supplementary materialThe online version of this article (doi:10.1007/s11136-013-0496-4) contains supplementary material, which is available to authorized users.

The effects of lead time and visual aids in TTO valuation: a study of the EQ-VT framework

BackgroundThe effect of lead time in time trade-off (TTO) valuation is not well understood. The purpose of this study was to investigate the effects on health-state valuation of the length of lead time and the way the lead-time TTO task is displayed visually.MethodsUsing two general population samples, we compared three lead-time TTO variants: 10 years of lead time in full health preceding 5 years of unhealthy time (standard); 5 years of lead time preceding 5 years of unhealthy time (experimental); and 10 years of lead time and 5 years of unhealthy time, presented with a visual aid to highlight the point where the lead time ends (experimental). Participants were randomized to receive one of the lead-time variants, as administered by a computer software program.ResultsHealth-state values generated by TTO valuation tasks using a longer lead time were slightly lower than those generated by tasks using a shorter lead time. When lead time and unhealthy time were presented with visual aids highlighting the difference between the lead time and unhealthy time, respondents spent more time considering health states with a value close to 0.ConclusionsDifferent lead-time time trade-off variants should be carefully studied in order to achieve the best measurement of health-state values using this new method.

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

This article examines the effect that different specifications of the time trade-off (TTO) valuation task may have on values for EQ-5D-5L health states. The new variants of the TTO, namely lead-time TTO and lag-time TTO, along with the classic approach to TTO were compared using two durations for the health states (15 and 20 years). The study tested whether these methods yield comparable health-state values. TTO tasks were administered online. It was found that lag-time TTO produced lower values than lead-time TTO and that the difference was larger in the longer time frame. Classic TTO values most resembled those of the lag-time TTO in a 20-year time frame in terms of mean absolute difference. The relative importance of different domains of health was systematically affected by the duration of the health state. In the tasks with a 10-year health-state duration, anxiety/depression had the largest negative impact on health-state values; in the tasks with a 5-year duration, the pain/discomfort domain had the largest negative impact.

One-to-one versus group setting for conducting computer-assisted TTO studies: findings from pilot studies in England and the Netherlands

We compare two settings for administering time trade-off (TTO) tasks in computer-assisted interviews (one-to-one, interviewer-led versus group, self-complete) by examining the quality of the data generated in pilot studies undertaken in England and the Netherlands. The two studies used near-identical methods, except that in England, data were collected in one-to-one interviews with substantial amounts of interviewer assistance, whereas in the Netherlands, the computer aid was used as a self-completion tool in group interviews with lesser amounts of interviewer assistance. In total, 801 members of the general public (403 in England; 398 in the Netherlands) each completed five TTO valuations of EQ-5D-5L health states. Respondents in the Netherlands study showed a greater tendency to give ‘round number’ values such as 0 and 1 and to complete tasks using a minimal number of iterative steps. They also showed a greater tendency to skip the animated instructions that preceded the first task and to take into account assumptions that they were specifically asked not to take into account. When faced with a pair of health states in which one state dominated the other, respondents in the Netherlands study were more likely than those in the England study to give a higher value to the dominant health state. On the basis of these comparisons, we conclude that the one-to-one, interviewer-led setting is superior to the group, self-complete setting in terms of the quality of data generated and that the former is more suitable than the latter for TTO studies being used to value EQ-5D-5L.

The valuation of the EQ-5D in Portugal

The EQ-5D is a preference-based measure widely used in cost-utility analysis (CUA). Several countries have conducted surveys to derive value sets, but this was not the case for Portugal. The purpose of this study was to estimate a value set for the EQ-5D for Portugal using the time trade-off (TTO). A representative sample of the Portuguese general population (n = 450) stratified by age and gender valued 24 health states. Face-to-face interviews were conducted by trained interviewers. Each respondent ranked and valued seven health states using the TTO. Several models were estimated at both the individual and aggregated levels to predict health state valuations. Alternative functional forms were considered to account for the skewed distribution of these valuations. The models were analyzed in terms of their coefficients, overall fit and the ability for predicting the TTO values. Random effects models were estimated using generalized least squares and were robust across model specification. The results are generally consistent with other value sets. This research provides the Portuguese EQ-5D value set based on the preferences of the Portuguese general population as measured by the TTO. This value set is recommended for use in CUA conducted in Portugal.

PRM124 - Examination of preferences elicited from the general public: Subgroup comparisons of results from the time trade-off and standard gamble instruments

The time trade-off (TTO) and the standard gamble (SG) are two methods used for the direct measurement of health-related quality of life, expressed as health utilities (HU), among the general public. Significant overall correlation was observed in a previous systematic review comparing TTO and SG values reported by the general public (19 pertinent publications, 77 study arms and 24 diseases). In the present analysis, correlation was further explored among specific demographic, clinical and analytic subgroups. When a sufficient sample of study arms was available, Spearman’s rank correlation test was applied to test the correlation between mean or median TTO and SG by sorting the TTO values in increasing increments of 0.1, based on the following subgroups: incremental HU, disease, gender, age, income, education level and employment status. Significance was defined as p-value<0.05. Significant positive correlation was observed between mean TTO and SG values for all increments of TTO except when TTO<0.5 (r = 0.429), for ocular disease (r = 0.976), skin disease (r = 0.964) and arthritis (r = 0.956). A post-hoc analysis quadrupling the sample of studies with TTO<0.5 resulted in significant positive correlation, indicating that the lack of significant correlation was possibly due to the scarcity of studies. The series of subgroup analyses focusing on median incremental HU values or median HU values associated with skin disease resulted in similar findings to the analysis of means. No analysis of demographic subgroups could be undertaken due to the limited study sample. A correlation between TTO and SG outcomes reported by members of the general public was observed for numerous subgroups. It is possible that correlation would have been observed in additional subgroups, but was not, due to the limited study sample.

PRM159 - The effect of lead time in time trade-off valuation of health states

PRM159 - The effect of lead time in time trade-off valuation of health states

A comparison of directly elicited and pre-scored preference-based measures of quality of life: the case of adhesive capsulitis

To assess the convergent validity and comparative responsiveness in measuring the health-related quality of life associated with adhesive capsulitis of a disease-specific measure (Shoulder Pain and Disability Index), a generic quality of life measure (SF-36), a preference-based multi-attribute utility scale (assessment of quality of life), and two direct patient preference elicitation methods (willingness to pay and time trade-off). Instruments administered to all 156 participants in both arms of a randomized placebo-controlled trial of physiotherapy following arthrographic joint distension at baseline were reported at 6, 12, and 26weeks. Convergent validity was measured using both pooled correlation between instruments and within subjects over time. Responsiveness was measured using the effect size for those with no improvement, moderate improvement, and marked improvement. With the exception of the monetary measure, all of the instruments showed a low quality of life at baseline with adhesive capsulitis (66- 87% of perfect health) and a substantial improvement in quality of life to week 26 on recovery. The time trade-off and willingness to pay measures of patient preferences were not responsive to changes in health, but all of the other instruments were at least moderately sensitive to change and moderately correlated with one another. These findings verify the significant adverse impact of adhesive capsulitis upon quality of life found in larger studies. There was a fair degree of convergence, as measured by the correlation between the instruments but while the time trade-off mean values were quite plausible, at a mean of 87% of full health before treatment, there was a low correlation with health profile and disease-specific measures. It may be that the time trade-off measured wider aspects of quality of life and that individuals were not prepared to trade survival for potential gains in a self-limiting condition.

DERIVING TIME DISCOUNTING CORRECTION FACTORS FOR TTO TARIFFS

The Time Trade-off (TTO) method is a popular method for valuing health state utilities and is frequently used in economic evaluations. However, this method produces utilities that are distorted by several biases. One important bias entails the failure to incorporate time discounting. This paper aims to measure time discounting for health outcomes in a sample representative for the general population. In particular, we estimate TTO scores alongside time discounting in order to derive a set of correction factors that can be employed to correct raw TTO scores for the downward bias caused by time discounting. We find substantial positive correction factors, which are increasing with the severity of the health state. Furthermore, higher discounting is found when using more severe health states in the discounting elicitation task. More research is needed to further develop discount rate elicitation procedures and test their validity, especially in general public samples. Moreover, future research should investigate the correction of TTO values for other biases as well, such as loss aversion, and to develop a criterion to test the external validity of TTO scores.

Societal Preferences for EQ-5D Health States from a Brazilian Population Survey

ObjectiveTo elicit preference weights for a subset of EuroQol five-dimensional (EQ-5D) questionnaire health states from a representative sample for the state of Minas Gerais, Brazil, using a time trade-off (TTO) method and to analyze these data so as to estimate social preference weights for the complete set of 243 states. MethodsData came from a valuation study with 3362 literate individuals aged between 18 and 64 years living in urban areas. The present study was based on quota sampling by age and sex. Face-to-face interviews were conducted in participants’ own homes. A total of 99 EQ-5D questionnaire health states were selected, presorted into 26 blocks of six unique health states. Each participant valued one block together with the full health, worst health, and dead states. Each health state was evaluated by more than 100 individuals. TTO data were modeled at both individual and aggregate levels by using ordinary least squares and random effects methods. ResultsValues estimated by different models yielded very similar results with satisfactory goodness-of-fit statistics: the mean absolute error was around 0.03 and fewer than 25% of the states had a mean absolute error greater than 0.05. Dummies coefficients for each level within the EQ-5D questionnaire dimensions of health displayed an internally consistent ordering, with the mobility dimension demonstrating the largest value decrement. The values of mean observed transformed TTO values range from 0.869 to−0.235. ConclusionsThe study demonstrates the feasibility of conducting face-to-face interviews using TTO in a Brazilian population setting. The estimated values for EQ-5D questionnaire health states based on this Minas Gerais survey represent an important first step in establishing national Brazilian social preference weights for the EQ-5D questionnaire.

Estimating quality weights for EQ-5D (EuroQol-5 dimensions) health states with the time trade-off method in Taiwan

EQ-5D (EuroQol-5 dimensions) is a preference-based measure of health, which is widely used in cost-utility analyses. It has been suggested that each country should develop its own value set. We therefore sought to develop the quality weights of the EQ-5D health states with the time trade-off (TTO) method in Taiwan. A total of 745 respondents consisting of employees and volunteers in 17 different hospitals were recruited and interviewed. Each of them valued 13 of 73 EQ-5D health states using the TTO method. Based on the three exclusion criteria for valuation data, only 456 (61.21%) respondents were considered eligible for data analysis. The quality weights for all EQ-5D health states were modeled by generalized estimating equations (GEEs). Over half of the responses were given negative values, and the medical personnel seemed to have a significantly higher TTO value (+0.1) than others after controlling for other predictors. The N3 model (level 3 occurred within at least 1 dimension) yielded an acceptable fit for the observed OTT data [mean absolute error (MAE)=0.056, R(2)=0.35]. The magnitude of mean absolute differences (MADs) between Taiwan data and those from the UK, Japan, and South Korea ranged from 0.146 to 0.592, but the rank correlation coefficients were all above 0.811. This study reaffirms the differences in health-related preference values across countries. The high proportion of negative values might indicate that we have also partially measured the intensity of fear in addition to the utility of different health states.

Utility Values for Advanced Soft Tissue Sarcoma Health States from the General Public in the United Kingdom

Soft tissue sarcomas are a rare type of cancer generally treated with palliative chemotherapy when in the advanced stage. There is a lack of published health utility data for locally advanced “inoperable”/metastatic disease (ASTS), essential for calculating the cost-effectiveness of current and future treatments. This study estimated time trade-off (TTO) and standard gamble (SG) preference values associated with four ASTS health states (progressive disease, stable disease, partial response, complete response) among members of the general public in the UK (n = 207). The four health states were associated with decreases in preference values from full health. Complete response was the most preferred health state (mean utility of 0.60 using TTO). The second most preferred health state was partial response followed by stable disease (mean utilities were 0.51 and 0.43, respectively, using TTO). The least preferred health state was progressive disease (mean utility of 0.30 using TTO). The utility value for each state was significantly different from one another (P < 0.001). This study demonstrated and quantified the impact that different treatment responses may have on the health-related quality of life of patients with ASTS.

Impact of Transformation of Negative Values and Regression Models on Differences Between the UK and US EQ-5D Time Trade-Off Value Sets

National EQ-5D value sets are developed because preferences for health may vary in different populations. UK values are lower than US values for most of the 243 possible EQ-5D health states. Although similar protocols were used for data collection, analytic choices regarding how to model values from the collected data may also influence national value sets. Participants in the UK and US studies assessed the same subset of 42 EQ-5D health states using the time trade-off (TTO) method. However, different methods were used to transform negative values to a range bounded by 0 and -1, and values for all 243 health states were estimated using two different regression models. The transformation of negative values is inconsistent with expected utility theory, and the choice of which transformation method to use lacks a theoretical foundation. Our objectives were to assess how much of the observed difference between the UK and US EQ-5D value sets may be explained by the choice of transformation method for negative values relative to the choice of regression model and the differences between elicited TTO values in the respective national studies (datasets). We applied both transformation methods and both regression models to each of the two datasets, resulting in eight comparable value sets. We arranged these value sets in pairs in which one source of difference (transformation method, regression model or dataset) was varied. For each of these paired value sets, we calculated the mean difference between the two matching values for each of the 243 health states. Finally, we calculated the mean utility gain for all possible transitions between pairs of EQ-5D health states within each value set and used the difference in transition scores as a measure of impact from changing transformation method, regression model or dataset. The mean absolute difference in values was 1.5 times larger when changing the transformation method than when using different datasets. The choice of transformation method had a 3.2 times larger effect on the mean health gain (transition score) than the choice of dataset. The mean health gain in the UK value set was 0.09 higher than in the US value set. Using the UK transformation method on the US dataset reduced this absolute difference to 0.02. The choice of regression model had little overall impact on the differences between the value sets. Most of the observed differences between the UK and US value sets were caused by the use of different transformation methods for negative values, rather than differences between the two study populations as reflected in the datasets. Changing the regression model had little impact on the differences between the value sets.

Estimating a Preference-Based Index from the Clinical Outcomes in Routine Evaluation–Outcome Measure (CORE-OM)

Background. The Clinical Outcomes in Routine Evaluation–Outcome Measure (CORE-OM) is used to evaluate the effectiveness of psychological therapies in people with common mental disorders. The objective of this study was to estimate a preference-based index for this population using CORE-6D, a health state classification system derived from the CORE-OM consisting of a 5-item emotional component and a physical item, and to demonstrate a novel method for generating states that are not orthogonal. Methods. Rasch analysis was used to identify 11 emotional health states from CORE-6D that were frequently observed in the study population and are, thus, plausible (in contrast, conventional statistical design might generate implausible states). Combined with the 3 response levels of the physical item of CORE-6D, they generate 33 plausible health states, 18 of which were selected for valuation. A valuation survey of 220 members of the public in South Yorkshire, United Kingdom, was undertaken using the time tradeoff (TTO) method. Regression analysis was subsequently used to predict values for all possible states described by CORE-6D. Results. A number of multivariate regression models were built to predict values for the 33 health states of CORE-6D, using the Rasch logit value of the emotional state and the response level of the physical item as independent variables. A cubic model with high predictive value (adjusted R2 = 0.990) was selected to predict TTO values for all 729 CORE-6D health states. Conclusion. The CORE-6D preference-based index will enable the assessment of cost-effectiveness of interventions for people with common mental disorders using existing and prospective CORE-OM data sets. The new method for generating states may be useful for other instruments with highly correlated dimensions.

PIH34 Identifying Individuals with Different Time Preferences in Time Trade-Off Valuations of Hypothetical Health States: A Latent Class Analysis of the US EQ-5D-3L Valuation Data

PIH34 Identifying Individuals with Different Time Preferences in Time Trade-Off Valuations of Hypothetical Health States: A Latent Class Analysis of the US EQ-5D-3L Valuation Data

The effect of chronic conditions on stated preferences for health

While patients tend to value their own health state systematically higher than others would rate it, it is less clear whether stated preferences for hypothetical health states differ between persons with and without specific medical conditions. The aim of this study was to determine if specific conditions affect the valuation of health using a generic measure. Using data from the US Valuation of EQ-5D Health States (n=3,773), we focused on six conditions of interest (COI), e.g., arthritis, diabetes, depression, heart failure, cancer, and hay fever, and time trade-off values for 12 of 243 EQ-5D health states. For each COI, regression models compared differences in pooled health state preferences among four groups: COI, COI plus one or more additional conditions, no COI but other conditions, or no chronic conditions. No differences in health state preferences were found among the four groups for any of the COIs except for patients with cancer and additional conditions, whose mean scores were 0.07 lower compared to no chronic conditions (P<0.01). The strongest predictors of health state preferences were race/ethnicity, age, and marital status. Most self-reported chronic conditions had a trivial impact on preferences for hypothetical health states, which suggests that utility algorithms for generic preference-based measures will be similar when estimated from preferences of the general population or patients with chronic illness, conceivably because both types of respondents have not experienced many health states in the classifier system.

Time trade-off and attitudes toward euthanasia: implications of using ‘death’ as an anchor in health state valuation

Health state values are by convention anchored to 'perfect health' and 'death.' Attitudes toward death may consequently influence the valuations. We used attitudes toward euthanasia (ATE) as a sub-construct for attitudes toward death. We compared the influence on values elicited with time trade-off (TTO), lead-time TTO (LT-TTO) and visual analogue scale (VAS).Since the 'death' anchor is most explicit in TTO, we hypothesized that TTO values would be most influenced by ATE. Respondents valued eight EQ-5D health states with VAS, then TTO (n=328) or LT-TTO (n=484). We measured ATE on a scale from -2 (fully disagree) to 2 (fully agree) and used multiple linear regressions to predict VAS, TTO, and LT-TTO values by ATE, sex, age, and education. A one-point increase on the ATE scale predicted a mean TTO value change of -.113 and LT-TTO change of -.072. Demographic variables, but not ATE, predicted VAS values. TTO appears to measure ATE in addition to preferences for health states. Different ways of incorporating death in the valuation may impact substantially on the resulting values. 'Death' is a metaphysically unknown concept, and implications of attitudes toward death should be investigated further to evaluate the appropriateness of using 'death' as an anchor.

Time Trade-Off and Ranking Exercises Are Sensitive to Different Dimensions of EQ-5D Health States

BackgroundOne method suggested for creating preference-based tariffs for the new five-level EuroQol five-dimensional (EQ-5D) questionnaire is combining time trade-off (TTO) and discrete choice exercises. Rank values from previous valuation studies can be used as proxies for discrete choice exercises. This study examined rank and TTO data to determine whether the methods differ in sensitivity to the EQ-5D questionnaire dimensions. MethodsWe used rank and TTO data for 42 EQ-5D questionnaire health states from the US and UK three-level EQ-5D questionnaire valuation studies, extracting overall ranks of mean TTO and mean rank values, ranging from 1 (best) to 42 (worst). We identified pairs of health states with reversed overall ranks between TTO and rank data and regressed overall rank differences (TTO – ranking) on dummy variables representing impairments on EQ-5D questionnaire dimensions. ResultsForty-three (US) and 41 (UK) health state pairs displayed reversed rank order. Both US and UK regression models on rank differences indicated that respondents rated impairments involving pain/discomfort and anxiety/depression as relatively worse in TTO than in the ranking task. DiscussionDifferent dimension sensitivity between TTO and ranking methods suggests that combining them could lead to inconsistent tariffs. Differences could be caused by respondents focusing on the first presented dimensions when ranking states or could be related to the longest endurable time for health states involving pain/discomfort or anxiety/depression. The observed differences call into question which method best represents the preferences of the population.

The Influence of Time and Adaptation on Health State Valuations in Patients With Spinal Cord Injury

One of the explanations for the difference between health state utilities elicited from patients and the public--often provided but seldom studied--is adaptation. The influence of adaptation on utilities was investigated in patients with spinal cord injury. Interviews were held at 3 time points (T1, after admission to the rehabilitation center; T2, during active rehabilitation; T3, at least half a year after discharge). At T1, 60 patients were interviewed; 10 patients withdrew at T2 and T3. At all time points, patients were asked to value their own health and a health state description of rheumatoid arthritis on a time trade-off and a visual analogue scale. The Barthel Index, a measure of independence from help in activities of daily living, and the adjustment ladder were filled out. Main analyses were performed using mixed linear models taking the time-dependent covariates (Barthel Index and adjustment ladder) into account. Time trade-off valuations for patients' own health changed over time, even after correction for gain in independence from help in activities of daily living, F(2, 59) = 8.86, P < 0.001. This change was related to overall adaptation. Both a main effect for adaptation, F(87, 1) = 10.05; P = 0.002, and an interaction effect between adaptation and time, F(41, 1)= 4.10, P = 0.024, were seen for time trade-off valuations. Valuations given for one's own health on the visual analogue scale did not significantly change over time, nor did the valuations for the hypothetical health state. Patients' health state valuations change over time, over and above the change expected by the rehabilitation process, and this change is partly explained by adaptation. Experience with a chronic illness did not lead to change in valuations of hypothetical health states.