Composite Time Trade-off Research Articles

Estimating Australian Population Utilities for Inherited Retinal Disease Using Time Trade-Off.

Inherited retinal disease (IRD) causes progressive loss of visual function, degenerating towards complete blindness. Economic evaluation of gene therapies for rare forms of genetic IRDs have had to rely on health-related quality of life (HR-QoL) estimates from other diseases because there is limited data available for such a rare condition. This study aimed to estimate Australian societal-based utility values for IRD health states that can be used in cost-utility analyses (CUA) using a time trade-off (TTO) protocol adapted from a UK study. The EuroQol Valuation Technology (EQVT) protocol composite TTO (cTTO) framework was followed, which includes worse-than-death (WTD) states and quality control (QC) measures. Preferences were collected from a general population sample of 110 Australian adult participants. Five health state vignettes from the UK study which had been validated with patients and clinicians were presented randomly to participants during videoconferencing (VC) interviews with one of four interviewers. Technical and protocol feasibility were assessed in a pilot of 10 interviews. QC measures were used to monitor interviewers' performance during the study. One participant withdrew consent. The final analysis was conducted on 109 respondents (including 4 non-traders). The average time to complete the interview was 44.2 minutes (SD 8.7). Participants reported mean visual analogue scale (VAS) scores between 63.15 for 'moderate impairment' and 17.98 for 'hand motion' to 'no light perception'. Mean health state utilities (HSU) varied between 0.76 (SD 0.26) in 'moderate impairment', and 0.20 (SD 0.58) in 'hand motion' to 'no light perception'. Of all HSU evaluations, 14% were considered WTD which most commonly occurred in the most severe visually impaired health state. This study provides valuable information on HSUs across a range of IRD health states from the Australian general population perspective. The utilities obtained in this study can be used as inputs into CUA of IRD therapies.

The EQ-5D-3L valuation study for Bermuda: using an on-line EQ-VT protocol.

In many countries, methods of economic evaluation and Health Technology Assessment are used to inform healthcare resource allocation decisions. These approaches often require EQ-5D health outcomes measures. This study aimed to create an EQ-5D-3L value set for Bermuda from which EQ-5D-5L Crosswalk values could be obtained. Respondents in Bermuda were recruited locally. A team of Trinidad-based interviewers with prior EQ-5D-3L valuation experience conducted valuation interviews on-line using the EQ-VT protocol. Respondents completed composite time-trade off (cTTO) and discrete choice experiment (DCE) tasks. A hybrid model that included both the cTTO and DCE data was estimated. An EQ-5D-5L crosswalk value set was then created from the EQ-5D-3L index values. Coefficients in the resulting crosswalk model were compared with those of crosswalk and valuation studies from other countries. The valuation tasks were completed by a near-representative sample of 366 adult Bermuda citizens. Half of the respondents reported being in state 11111. The lowest EQ VAS and EQ-5D-3L index values were 20 and -0.120 respectively. The hybrid model produced all logically consistent and statistically significant coefficients that in turn produced index values that were very similar to those obtained in a preliminary model (MAD of 0.027). The on-line EQ-VT valuation study was successfully conducted in Bermuda and the values therein can now be used for economic analysis in Bermuda. The Bermuda values differed considerably from those of the other countries against which they were compared. Challenges were encountered with recruitment for an on-line survey in a small population.

A New and Improved Experimental Design for the Discrete Choice Experiment Module of the EuroQol Valuation Technology Protocol

ObjectivesThe EuroQol Valuation Technology (EQ-VT) protocol, which is used to value the EQ-5D-5L instrument, comprises a composite time trade-off and a discrete choice experiment (DCE) module. Despite significant limitations, the DCE module has not been updated since its inception in 2012. This study aimed to update the EQ-VT DCE design using state-of-the-art methods. MethodsDCE data from 19 EQ-5D-5L valuation studies were summarized using a Bayesian hierarchical meta-analysis model, which created the priors for our Bayesian efficient DCE design. This design comprised 20 subdesigns, each with 12 choice tasks, and included 2 levels that overlapped to reduce the complexity of the choice tasks. The relative efficiency and robustness of the new design were established by comparing the D-errors and minimal sample size requirements for the 19 within-sample and 7 out-of-sample countries with the previous DCE design. ResultsThe updated DCE design shows large reductions in the D-error: by 20% and 22% for the 19 within-sample and 7 out-of-sample countries, respectively. Sample size requirements were also reduced, resulting in an average reduction of 45% for both the within and out-of-sample countries. ConclusionsThe updated DCE design outperforms the current EQ-VT design. Given its enhanced performance and reduced complexity, it is set to replace the existing DCE design in future EQ-5D-5L valuation studies using the EQ-VT protocol.

Estimating an EQ-5D-Y-3L Value Set for Brazil.

The EQ-5D-Y-3L is a generic measure of health-related quality of life in children and adolescents. Although the Brazilian-Portuguese EQ-5D-Y-3L version is available, there is no value set for it, hampering its use in economic evaluations. This study aimed to elicit a Brazilian EQ-5D-Y-3L value set based on preferences of the general adult population. Two independent samples of adults participated in an online discrete choice experiment (DCE) survey and a composite time trade-off (cTTO) face-to-face interview. The framing was "considering your views for a 10-year-old child". DCE data were analyzed using a mixed-logit model. The 243 DCE predicted values were mapped into the observed 28 cTTO values using linear and non-linear mapping approaches with and without intercept. Mapping approaches' performance was assessed to estimate the most valid method to rescale DCE predicted values using the model fit (R2), Akaike Information Criteria (AIC), root mean squared error (RMSE), and mean absolute error (MAE). A representative sample of 1376 Brazilian adults participated (DCE, 1152; cTTO, 211). The linear mapping without intercept (R2 = 96%; AIC, - 44; RMSE, 0.0803; MAE, - 0.0479) outperformed the non-linear without intercept (R2 = 98%; AIC, - 63; RMSE, 0.1385; MAE, - 0.1320). Utilities ranged from 1 (full health) to - 0.0059 (the worst health state). Highest weights were assigned to having pain or discomfort (pain/discomfort), followed by walking about (mobility), looking after myself (self-care), doing usual activities (usual activities), and feeling worried, sad, or unhappy (anxiety/depression). This study elicited the Brazilian EQ-5D-Y-3L value set using a mixed-logit DCE model with a power parameter based on a linear mapping without intercept, which can be used to estimate the quality-adjusted life-years for economic evaluations of health technologies targeting the Brazilian youth population.

The EQ-5D-5L valuation study for Trinidad and Tobago

PurposeThe 2016 EQ-5D-3L value set for Trinidad and Tobago (T&T) allows for the calculation of EQ-5D-5L values via the crosswalk algorithm. The 2016 value set was based on methods predating the EQ-VT protocol, now considered the gold standard for developing EQ-5D value sets. Furthermore, direct elicitation of EQ-5D-5L is preferred over crosswalked values. This study aimed to produce an EQ-5D-5L value set for T&T.MethodsA representative sample (age, sex, geography) of adults each completed 10 composite Time Trade-Off (cTTO) tasks and 12 Discrete Choice Experiment (DCE) tasks in face-to-face interviews. The cTTO data were analyzed using a Tobit model that corrects for heteroskedasticity. DCE data were analyzed using a mixed logit model. The cTTO and DCE data were combined in hybrid models.ResultsOne thousand and seventy-nine adults completed the valuation interviews. Among the modelling approaches that were explored, the hybrid heteroskedastic Tobit model produced all internally consistent, statistically significant coefficients, and performed best in terms of out-of-sample predictivity for single states. Compared to the existing EQ-5D-5L crosswalk set, the new value set had a higher number of negative values (236 or 7.6% versus 21 or 0.7%). The mean absolute difference was 0.157 and the correlation coefficient between the two sets was 0.879.ConclusionThis study provides a value set for the EQ-5D-5L for T&T using the EQ-VT protocol. We recommend this value set for QALY computations relating to T&T.

Valuation of Multi-Dimensional Health States With a Bolt-On: Is There a Shortcut?

ObjectivesTo use the EQ-5D questionnaire with bolt-on dimensions in economic evaluation studies, new value sets are needed. In this study, we explored the feasibility of a new approach called the scaling factor model, which estimates bolt-on value sets using estimated EQ-5D dimensional weights. MethodsWe designed a 2-arm study, inviting university students to value health states with and without bolt-on items using the composite time trade-off method. We selected 25 health states from an orthogonal array and added the 5 mildest EQ-5D states in the design. In arm 1, EQ-5D without self-care and standard EQ-5D states were valued, and in arm 2, standard EQ-5D states and EQ-5D with vision were valued. By arm, we compared the mean observed values of health states with and without bolt-on item. Next, by arm, we estimated value sets for the EQ-5D with bolt-on states using both standard model and scaling factor model. Model performances were compared in terms of prediction accuracy and correlation with likelihood-based mean values. ResultsAdding a five-level bolt-on to EQ-5D resulted in statistically lower values. This effect was consistent across 2 arms and bolt-on items. The scaling factor models outperformed the standard models in all statistics. ConclusionsThe scaling factor model offers a methodologically viable and low-cost option for producing value sets for EQ-5D supplemented with bolt-on items. Future studies should further test this method using other bolt-on items and more relevant study populations.

A Direct Comparison Between Discrete Choice With Duration and Composite Time Trade-Off Methods: Do They Produce Similar Results?

ObjectivesDiscrete choice experiments including a duration attribute (DCEd) represent a promising candidate method for valuing health-related quality-of-life instruments. However, it has not been established that DCEd can produce similar results as composite time trade-off (cTTO) or EuroQol Valuation Technology (EQ-VT) valuations of the EQ-5D-5L instrument. This study provides a direct comparison between cTTO and EQ-VT, and DCEd valuation methods. MethodsAn EQ-VT study was conducted in Trinidad and Tobago to value the EQ-5D-5L. 1079 respondents each completed 10 cTTO tasks and 12 discrete choice experiments tasks without a duration attribute. A separate sample of 970 respondents each completed 18 split-triplet DCEd tasks. Several regression models were applied to the EQ-VT data, and the DCEd data were analyzed using mixed logit models with an exponential discount rate. The estimated values were compared using scatterplots and Bland-Altman plots. ResultsThe ordering of dimensions was identical in level 5 for cTTO/EQ-VT and DCEd models, with pain/discomfort being the most important dimension and usual activities being least important. cTTO/EQ-VT models produced a value for state 55555 ranging between −0.52 and −0.69, whereas this was −0.543 for the nonlinear mixed logit model for the DCEd data. Scatterplots and Bland-Altman plots suggested excellent agreement between cTTO/EQ-VT and DCEd-based estimates. ConclusionsCTTO/EQ-VT and DCEd valuations produce similar results when correcting DCEd for nonlinear time preferences. The ordering of importance of the dimensions and scale are identical, suggesting that the 2 methods measure the same construct and produce similar results.

Comparison of four value sets derived using different TTO and DCE approaches: application to the new region-specific PBM, AP-7D

BackgroundAP-7D is a newly developed preference-based measure (PBM) in East and Southeast Asia. However, no value set has been established yet. Comparison of the characteristics of value sets obtained by different methods is necessary to consider the most appropriate methodology for valuation survey of AP-7D.MethodWe surveyed the general population’s preference of AP-7D health states by four valuation methods (a) composite time trade-off (cTTO); (b) simple discrete choice experiment (DCE); (c) DCE with duration; and (d) ternary DCE. In Japan, we collected approximately 1,000 samples for cTTO tasks through a face-to-face survey and 2,500 samples for each of the three DCE tasks. Respondents were selected through quota sampling based on the sex and age. The cTTO data were analyzed using a linear mixed and tobit model; the DCE data were analyzed using a simple and panel conditional logit model. Where the results of the analysis showed inconsistencies, a constrained model was used.ResultsSince all the unconstrained models, except simple DCE, showed one or more inconsistencies, the constrained model was used for the analyses. The minimum values for the models were as follows: TTO model, -0.101; simple DCE model, -0.106; DCE with duration model, -0.706; ternary DCE model, -0.306. The score for the DCE with the duration model was much lower than that for the other models. Although the value sets for AP-7D differed among the four valuation methods, the ternary DCE model showed intermediate characteristics between those of the cTTO and DCE with duration models. As compared with to EQ-5D-5L, the distributions of all the scores on the Japanese AP-7D moved to the left. Although “Energy” was one of the domains with the least influence on the AP-7D score in all four models, “Burden to others” had the largest impact on the preferences.ConclusionWe constructed four value sets using different TTO and DCE methods. Our findings are expected not only to contribute to the development of AP-7D, but also other preference-based measures.

Comparing heuristic valuation processes between health state valuation from child and adult perspectives

ObjectivesHealth state valuation assumes that respondents trade off between all aspects of choice tasks and maximize their utility. Yet, respondents may use heuristic valuation processes, i.e., strategies to simplify or avoid the trade-offs that are core to health state valuation. The objective of this study is to explore if heuristic valuation processes are more prevalent for valuation from a 10-year-old child’s perspective compared to the use of an adult perspective.MethodsWe reused existing data in which EQ-5D health states were valued from adult and child perspectives with composite time trade-off (cTTO) and discrete choice experiment (DCE) tasks. Our analyses focused on comparing completion time and responding patterns across both perspectives. We also explored how reflective of a set of heuristic strategies respondents’ choices were in both perspectives.ResultsWe found no evidence for systematic differences in completion time across perspectives. Generally, we find different responding patterns in child perspectives, e.g., more speeding, dominance violations, and clustering of utilities at 1.0, 0.8, and 0. Very few heuristic strategies provide a coherent explanation for the observed DCE responses.ConclusionOur results provide some, albeit indirect, evidence for differences in heuristic valuation processes between perspectives, although not across all data sources. Potential effects of heuristic valuation processes, such as transfer of responsibility, may be identified through studying responding patterns in cTTO and DCE responses.

Are Web-Based Valuation Surveys for Preference-Based Measures as Reliable as Face-to-Face Surveys? TTO, DCE and DCE with Duration.

Valuation surveys of preference-based measures are typically conducted face-to-face or on web panels. In this survey, we considered whether face-to-face and online surveys were reliable using three tasks: composite time trade-off (cTTO), discrete choice experiment (DCE), and DCE with duration. Respondents (aged 20-69 years) for both face-to-face (N = 1000, target sample size) and web surveys were selected through quota sampling by sex and age from each panel of the general population in Japan. They were then allocated to one of the three tasks and divided into six groups (two survey modes × three tasks, N = 334 per group). For the cTTO, respondents were asked to rate ten health states described by the EQ-5D-5L. For the DCE and DCE with duration surveys, respondents were asked about 15 health-state pairs. For all participants, as in the second-stage survey, a similar process was repeated two weeks after the first survey. Reliability was evaluated by calculating the percentage of agreement and intraclass correlation coefficients. The cTTO scores of the face-to-face and web surveys were systematically different. Between the face-to-face and web surveys, the agreement of the TTO survey was not good. The intraclass correlation coefficient (ICC) was 0.37 for the face-to-face test-test and 0.59 for the web test-retest. Discrete choice experiment (DCE) and DCE with duration had similarly good agreement (more than 70%), regardless of face-to-face or web surveys. However, between the first and second surveys (test-retest) of DCE and DCE with duration, the agreement depends on whether the positions of the two cards (health states) are identical. If the face-to-face cTTO score is the gold standard, a web-based survey of cTTO is not recommended regardless of the ICC. If a DCE survey is performed, positioning effects should be considered.

Health State Utilities Associated with False-Positive Cancer Screening Results.

Early cancer detection can significantly improve patient outcomes and reduce mortality rates. Novel cancer screening approaches, including multi-cancer early detection tests, have been developed. Cost-utility analyses will be needed to examine their value, and these models require health state utilities. The purpose of this study was to estimate the disutility (i.e., decrease in health state utility) associated with false-positive cancer screening results. In composite time trade-off interviews using a 1-year time horizon, UK general population participants valued 10 health state vignettes describing cancer screening with true-negative or false-positive results. Each false-positive vignette described a common diagnostic pathway following a false-positive result suggesting lung, colorectal, breast, or pancreatic cancer. Every pathway ended with a negative result (no cancer detected). The disutility of each false positive was calculated as the difference between the true-negative and each false-positive health state, and because of the 1-year time horizon, each disutility can be interpreted as a quality-adjusted life-year decrement associated with each type of false-positive experience. A total of 203 participants completed interviews (49.8% male; mean age = 42.0 years). The mean (SD) utility for the health state describing a true-negative result was 0.958 (0.065). Utilities for false-positive health states ranged from 0.847 (0.145) to 0.932 (0.059). Disutilities for false positives ranged from -0.031 to -0.111 (-0.041 to -0.111 for lung cancer; -0.079 for colorectal cancer; -0.031 to -0.067 for breast cancer; -0.048 to -0.088 for pancreatic cancer). All false-positive results were associated with a disutility. Greater disutility was associated with more invasive follow-up diagnostic procedures, longer duration of uncertainty regarding the eventual diagnosis, and perceived severity of the suspected cancer type. Utility values estimated in this study would be useful for economic modeling examining the value of cancer screening procedures.

Quality-of-life survey of pancreatic cancer patients: a comparison between general public and physicians.

Quality-of-life (QOL) is important for cancer patients with poor prognosis. However, conducting a QOL survey with patients is difficult. Therefore, we conducted a QOL survey with physicians. Specifically, this study aimed to clarify how physicians assess QOL in patients with pancreatic cancer by conducting a survey and comparing the results between physicians and the general public. A survey was conducted by interviewing physicians administering chemotherapy to patients for recurrent/metastatic pancreatic cancer. This method is similar to that of the QOL survey conducted among the general public. Responses were evaluated using the composite time trade-off (cTTO) and the visual analog scale (VAS) for 11 pancreatic cancer status scenarios (survey scenarios). These scenarios consisted of patients' health states as well as the types and grades of adverse events (AEs). Health status was classified into two categories: Stable disease (SD) and Progressive disease (PD). In addition, we conducted a survey using the EuroQol 5 Dimensions 5-Level (EQ-5D-5l) as reference values. Twenty physicians responded to the survey. SD had the highest mean QOL value for both assessment methods (Physicians: 0.78, General public: 0.63), whereas PD had the lowest mean QOL value (Physicians: 0.15, General public: -0.12). The physicians assigned higher QOL values on both the VAS and cTTO than the general public did in all survey scenarios. The QOL values obtained from physicians were consistent with the degree of status in any assessment scenarios. Based on the differences in the QOL survey results between physicians and the general public, physicians tended to assign higher QOL values than the general public in cTTO and VAS assessments.

Beyond 10-year lead-times in EQ-5D-5L: leveraging alternative lead-times in willingness-to-accept questions to capture preferences for worse-than-dead states and their implication.

A fixed 10-year lead-time in composite time-trade-off (C-TTO) tasks might compromise the precision of utility values below -1. This study explored how alternative lead-times (ALTs) influence EQ-5D-5L value sets and their implications in economic evaluations. Leveraging data from Taiwan's EQ-5D-5L valuation and capitalizing on its exploratory willingness-to-accept question, we explored participants' quantification of "worse-than-dead (WTD)" health states with ALTs up to 50years. We then derived alternative value sets incorporating these ALTs through interval regression and compared them against those from conventional models. To evaluate their impact on health change valuation, we simulated utility differences for all possible EQ-5D-5L health-state-pairs using each value set. With a salient floor effect observed in the C-TTO values, the model with ALT led to a wider range of predicted utilities ( - 2.3897 ~ 1), compared with those of conventional models (generalized least squares (GLS): - 0.7773 ~ 1; Tobit-GLS: - 0.9583 ~ 1). Compared to the Tobit-GLS model, the model with ALT increased the numerical distance in 80% of health-state-pairs, with 11% decreasing and 9% altering direction (e.g., positive to negative) in utility differences. While ALTs offer insights into patient preferences, their integration into economic evaluations might require rescaling. Future research should prioritize advanced rescaling methods or enhanced elicitation strategies for populations with substantial censoring. This is pivotal for improving the elicitation of extreme WTD states and accurately discerning the relative distances between health states. Countries developing EQ-5D-5L value sets should consider pilot studies and incorporating region-specific questions on social determinants, especially where pronounced floor effects are suspected.

Re-revisiting the Utilities of Health States Worse than Dead: The Problem Remains.

In valuation studies of the EQ-5D-5L instrument, the composite time tradeoff method (cTTO) is often used to elicit preferences. In cTTO, some health states are considered worse than dead (WTD) and are assigned negative utility values. However, these negative values correlate poorly with state severity, which suggests that cTTO is insufficiently sensitive. A recent threshold explanation has been offered to account for the lack of correlation: because the severity threshold beyond which a state is considered WTD differs between respondents, the correlation should be studied for individual respondents clustered by the number of WTD states. The results obtained in such a threshold approach were interpreted to disprove the insensitivity of the cTTO method. To scrutinize the threshold explanation and test whether it indeed refutes the insensitivity of cTTO. The study uses data from the EQ-5D-5L Polish valuation study, which includes cTTO responses from 1,510 participants, each of whom evaluated 10 EQ-5D-5L states. The correlation analysis and threshold approach are repeated to confirm the results from previous studies. The data are then modified in 2 contrasting ways. First, negative utilities are randomly reshuffled to test whether the threshold approach can capture cTTO insensitivity. Second, individual-level regressions are used to simulate negative values to ensure they correlate with severity at the individual respondent level, verifying whether the overall severity-utility correlation should be observed. First, reshuffling negative utilities does not change the results of the threshold approach. Hence, the threshold explanation fails to prove cTTO sensitivity. Second, when sensitivity was introduced on an individual level, a significant overall correlation between severity and negative utility arose. cTTO is insensitive to severity for WTD states. For the composite time tradeoff method, the utility values of health states worse than dead correlate poorly with state severity, which suggests that cTTO has insufficient sensitivity.Recently, a so-called threshold explanation was offered for the lack of correlation.I show why the threshold explanation fails and why the composite time tradeoff is indeed insensitive for worse-than-dead states.

UK Valuation of EQ-5D-5L, a Generic Measure of Health-Related Quality of Life: A Study Protocol

ObjectivesA high-quality and widely accepted UK EQ-5D-5L value set is urgently required to enable the latest version of EQ-5D scored using recent UK public preferences to inform policy including health technology assessments submitted to the National Institute for Health and Care Excellence. This article outlines the study protocol for the generation of a new EQ-5D-5L UK value set. MethodsTwelve hundred interviews will be undertaken using the composite time trade-off elicitation technique for 102 health states (86 from the international EQ-5D-5L valuation protocol, plus 16 with best predictive performance in an extended design used in the Native American EQ-5D-5L valuation). The sample will be UK adults (age ≥18 years) proportionately representative across England, Wales, Scotland, and Northern Ireland, representative for age, sex, ethnicity, and socioeconomic group, with inclusion of participants with/without health problems. Participants will choose to be interviewed via videoconference (by Zoom) or in-person in a central venue. Data quality will be rigorously assessed. ResultsThe value set will be generated using tobit random effects and heteroscedastic tobit models (with censoring at −1) using all data, excluding time trade-off values highlighted by participants as ones they would reconsider and data from interviewers failing protocol compliance. Quality and acceptance will be achieved by public involvement, regular Steering Group meetings, independent assessment of data quality at 4 time points, and final endorsement of data and analyses. ConclusionThis study will produce a UK value set for the EQ-5D-5L for use in prospective and retrospective data sets containing EQ-5D-5L data.

The EQ-5D-3L Valuation Study in Pakistan.

To utilize EQ-5D in economic evaluations, a societal-based value set is needed. To date, no value sets exist for any EQ-5D instrument in Pakistan. Previous EQ-5D studies conducted in Pakistan 'borrowed' health preferences developed in other countries. However, for a value set to be valid for Pakistani population, it should represent the preferences of the Pakistani population, and culture and living standards of Pakistan. The aim of this study was to derive a Pakistani EQ-5D-3L value set. A moderately representative sample aged 18 years and over was recruited from the Pakistani general population. A multi-stage stratified quota method with respect to ethnicity, gender, age and religion was utilized. Two elicitation techniques, the composite time trade-off (cTTO) and discrete choice experiments (DCE) were applied. Interviews were undertaken by trained interviewers using computer-assisted face-to-face interviews with the EuroQol Portable Valuation Technology (EQ-PVT) platform. To estimate the value set, a hybrid regression model combining cTTO and DCE data was used. A total of 289 respondents who completed the interviews were included for the analysis. The hybrid model correcting for heteroskedasticity without a constant was selected as the final model for the value set. It is shown that being unable to do usual activities (level 3) was assigned the largest weight, followed by mobility level 3, self-care level 3, pain/discomfort level 3 and anxiety/depression level 3. The worst health state was assigned the value - 0.171 in the final model. A Pakistani country-specific EQ-5D-3L value set is now available. The availability of this value set may help promote and facilitate health economic evaluations and health-related quality-of-life (HRQoL) research in Pakistan.

Societal Utilities for Cognitive Impairment in Schizophrenia: Developing a Preference-Based Scoring Algorithm Based on the Schizophrenia Cognition Rating Scale.

Loss of cognitive function is a common feature in schizophrenia. However, generic measures of health-related quality of life favored by decision-makers, such as the EQ-5D, are not designed to detect changes in cognitive function. We report the valuation of the Schizophrenia Cognition Rating Scale (SCoRS), a schizophrenia-specific measure of cognitive impairment. Expert opinion and psychometric analysis of the SCoRS from clinical trial data was undertaken to select 5 key items from the measure. These items were combined orthogonally to develop health-state vignettes. Vignettes were valued using composite time trade-off (cTTO) in one-on-one video calls. Several econometric models were fitted to the data to estimate disutilities. Performance of EQ-5D- and SCoRS-based utilities were compared in the trial data. The SCoRS items selected for the valuation study represented attention, learning, processing speed, social cognition and memory. Four hundred respondents participated in the valuation study. The best observed health state was valued at 0.855 [standard deviation (SD)=0.179] and the worst at 0.152 (SD=0.575). At the most severe levels, 'social cognition' received the largest disutility followed by 'learning' and 'memory'. The final model to estimate utilities had 15 parameters. SCoRS-based utilities were sensitive to change in cognition, but the EQ-5D was not. It is feasible to value different dimensions of cognition separately using a validated instrument for proxy assessment. The resulting utilities indicate loss of quality of life due to reduced cognitive functioning.

The effect of duration and time preference on the gap between adult and child health state valuations in time trade-off

Composite time trade-off (cTTO) utilities have been found to be higher when adults value health states for children than for themselves. It is not clear if these differences reflect adults assigning truly higher utilities to the same health state in different perspectives, or if they are caused by other factors, which are not accounted for in the valuation procedure. We test if the difference between children’s and adults’ cTTO valuations changes if a longer duration than the standard 10 years is used. Personal interviews with a representative sample of 151 adults in the UK were conducted. We employed the cTTO method to estimate utilities of four different health states, where adults considered states both from their own and a 10-year-old child’s perspective, for durations of 10 and 20 years. We corrected the cTTO valuations for perspective-specific time preferences in a separate task, again for both perspectives. We replicate the finding that cTTO utilities are higher for the child perspective than for the adult perspective, although the difference is only significant when controlling for other variables in a mixed effects regression. Time preferences are close to 0 on average, and smaller for children than adults. After correcting TTO utilities for time preferences, the effect of perspective is no longer significant. No differences were found for cTTO tasks completed with a 10- or 20-year duration. Our results suggest that the child–adult gap is partially related to differences in time preferences and, hence, that correcting cTTO utilities for these preferences could be useful.

EQ-5D-5L Value Set for Slovenia.

The aim of this valuation study was to produce a value set to support the use of EQ-5D-5L data in decision making in Slovenia. The study design followed the published EuroQol research protocol, and a quota sample was defined according to age, sex, and region. Overall, 1012 adult respondents completed 10 time trade-off and seven discrete choice experiment tasks in face-to-face interviews. The Tobit model was used to analyse the composite time trade-off (cTTO) data in order to generate values for the 3125 EQ-5D-5L health states. The data showed logical consistency, with more severe states being given lower values. The greatest disutility was shown in the pain/discomfort and anxiety/depression dimensions. In the EQ-5D-5L value set, the values range from -1.09 to 1. With the exception of UA5 (unable to perform usual activities), all other levels on all health dimensions were statistically different from 0 and from each other.Compared with the existing EQ-5D-3L value set, there is a slightly lower share of 'worse than dead' states (32.1% compared with 33.7%) and the minimum value is lower. Results have important implications for users of the EQ-5D-5L in Slovenia and regions. It is a robust and up-to-date value set and should be the preferred value set used in adults in Slovenia and in neighbouring countries without their own value set.

Derivation of a UK preference-based value set for the Short Warwick-Edinburgh Mental Well-being Scale (SWEMWBS) to allow estimation of Mental Well-being Adjusted Life Years (MWALYs)

BackgroundThe Mental Well-being Adjusted Life Year (MWALY) is an alternative outcome measure to the quality-adjusted life year (QALY) in economic evaluations of interventions aimed at improving mental well-being. However, there is a lack of preference-based mental well-being instruments for capturing population mental well-being preferences. ObjectivesTo derive a UK preference-based value set for the Short Warwick-Edinburgh Mental Well-being Scale (SWEMWBS). Methods225 participants that were interviewed between December 2020 and August 2021 completed 10 composite time trade-off (C-TTO) and 10 discrete choice experiment (DCE) interviewer-administered exercises. Heteroskedastic Tobit and conditional logit models were used to model C-TTO and DCE responses respectively. The DCE utility values were rescaled to a C-TTO comparable scale through anchoring and mapping. An inverse variance weighting hybrid model (IVWHM) was used to derive weighted-average coefficients from the modelled C-TTO and DCE coefficients. Model performance was assessed using statistical diagnostics. ResultsThe valuation responses confirmed the feasibility and face validity of the C-TTO and DCE techniques. Apart from the main effects models, statistically significant associations were estimated between the predicted C-TTO value and participants’ SWEMWBS scores, gender, ethnicities, education levels, and the interaction terms between age and useful feeling. The IVWHM was the most optimal model with the fewest logically inconsistent coefficients and the lowest pooled standard errors. The utility values generated by the rescaled DCE models and the IVWHM were generally higher than those of the C-TTO model. The predictive ability of the two DCE rescaling methods was similar according to the mean absolute deviation and root mean square deviation statistics. ConclusionsThis study has produced the first preference-based value set for a measure of mental well-being. The IVWHM provided a desirable blend of both C-TTO and DCE models. The value set derived by this hybrid approach can be used for cost-utility analyses of mental well-being interventions.