A fallacy of the multiplicative QALY model for low-quality weights in students and patients judging hypothetical health states

Testing Nonmonotonicity in Health Preferences

OBJECTIVE

The main aim of this article is to test monotonicity in life duration. Previous findings suggest that, for poor health states, longer durations are preferred to shorter durations up to some threshold or maximum endurable time (MET), and shorter durations are preferred to longer ones after that threshold.

METHODS

Monotonicity in duration is tested through 2 ordinal tasks: choices and rankings. A convenience sample (n = 90) was recruited in a series of experimental sessions in which participants had to rank-order health episodes and to choose between them, presented in pairs. Health episodes result from the combination of 7 EQ-5D-3L health states and 5 durations. Monotonicity is tested comparing the percentage rate of participants whose preferences were monotonic with the percentage of participants with nonmonotonic preferences for each health state. In addition, to test the existence of preference reversals, we analyze the fraction of people who switch their preference from rankings to choices.

RESULTS

Monotonicity is frequently violated across the 7 EQ-5D health states. Preference patterns for individuals describe violations ranging from almost 49% with choices to about 71% with rankings. Analysis performed by separate states shows that the mean rates of violations with choices and ranking are about 22% and 34%, respectively. We also find new evidence of preference reversals and some evidence-though scarce-of transitivity violations in choices.

CONCLUSIONS

Our results show that there is a medium range of health states for which preferences are nonmonotonic. These findings support previous evidence on MET preferences and introduce a new "choice-ranking" preference reversal. It seems that the use of 2 tasks with a similar response scale may make preference reversals less substantial, although it remains important and systematic.

HIGHLIGHTS

Two procedures based on ordinal comparisons are used to elicit preferences: direct choices and rankings. Our study reports significant rates of nonmonotonic preferences (or maximum endurable time [MET]-type preferences) for different combinations of durations and EQ-5D health states.Analysis for separate health states shows that the mean rates of nonmonotonicity range from 22% (choices) to 34% (rankings), but within-subject analysis shows that nonmonotonicity is even higher, ranging from 49% (choices) to 71% (rankings). These violations challenge the validity of multiplicative QALY models.We find that the MET phenomenon may affect particularly those EQ-5D health states that are in the middle of the severity scale and not so much the extreme health states (i.e., very mild and very severe states).We find new evidence of preference reversals even using 2 procedures of a similar (ordinal) nature. Percentage rates of preference reversals range from 1.5% to 33%. We also find some (although scarce) evidence on violations of transitivity.

The clinical and economic value of a successful shutdown during the SARS-CoV-2 pandemic in Germany

BACKGROUND AND AIM

A shutdown of businesses enacted during the SARS-CoV-2 pandemic can serve different goals, e.g., preventing the intensive care unit (ICU) capacity from being overwhelmed ('flattening the curve') or keeping the reproduction number substantially below one ('squashing the curve'). The aim of this study was to determine the clinical and economic value of a shutdown that is successful in 'flattening' or 'squashing the curve' in Germany.

METHODS

In the base case, the study compared a successful shutdown to a worst-case scenario with no ICU capacity left to treat COVID-19 patients. To this end, a decision model was developed using, e.g., information on age-specific fatality rates, ICU outcomes, and the herd protection threshold. The value of an additional life year was borrowed from new, innovative oncological drugs, as cancer reflects a condition with a similar morbidity and mortality burden in the general population in the short term as COVID-19.

RESULTS

A shutdown that is successful in 'flattening the curve' is projected to yield an average health gain between 0.01 and 0.05 life years (0.1 to 0.6 months) per capita in the German population. The corresponding economic value ranges between €616 and €4797 per capita or, extrapolated to the total population, 1%-12% of the gross domestic product (GDP) in 2019. A shutdown that is successful in 'squashing the curve' is expected to yield a minimum health gain of 0.08 life years (1 month) per capita, corresponding to 19 % of the GDP in 2019. Results are particularly sensitive to mortality data and the prevalence of undetected cases.

CONCLUSION

A successful shutdown is forecasted to yield a considerable gain in life years in the German population. Nevertheless, questions around the affordability and underfunding of other parts of the healthcare system emerge.

Monthly migraine days, tablet utilization, and quality of life associated with Rimegepant - post hoc results from an open label safety study (BHV3000-201)

Background

The objective of this study was to describe patterns in monthly migraine days (MMD) and tablet utilization, and to estimate health-related quality of life (HRQoL) measures in patients treated as needed (PRN) with rimegepant 75 mg over 52-weeks.

Methods

Eligible subjects were adults with ≥1 year history of migraine and ≥ 6 MMD at baseline, who used rimegepant 75 mg up to once daily PRN (at their discretion) for up to 52-weeks in an open-label safety study (BHV3000–201; NCT03266588). Mean MMD were calculated at each 4-week period, along with mean monthly tablets taken. Migraine-specific quality of life (MSQv2) data were mapped to EQ-5D utilities and used to characterize HRQoL over time. A published network meta-analysis was used to characterize pain hours as well as time periods spent migraine free.

Results

One thousand forty four subjects were included in this post-hoc analysis. Overall mean MMD were 10.9 at baseline and decreased to 8.9 by week 52. Tablet use remained stable over the follow-up period. A total of 0.08 incremental QALYs were associated with rimegepant use.

Conclusion

For subjects with 6 or more MMD, acute treatment of migraine attacks with rimegepant 75 mg on a PRN basis over one-year of follow-up was found to be associated with reduced MMD frequency without an increase in monthly tablet utilization, and improved HRQoL. There was no evidence of medication-related increases in MMDs when rimegepant 75 mg was used as needed for the acute treatment of migraine over 52-weeks.

Trial registration

ClinicalTrials.gov identifier NCT03266588.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10194-021-01378-5.

How Many Intensive Care Beds are Justifiable for Hospital Pandemic Preparedness? A Cost-effectiveness Analysis for COVID-19 in Germany

INTRODUCTION

Germany is experiencing the second COVID-19 pandemic wave. The intensive care unit (ICU) bed capacity is an important consideration in the response to the pandemic. The purpose of this study was to determine the costs and benefits of maintaining or expanding a staffed ICU bed reserve capacity in Germany.

METHODS

This study compared the provision of additional capacity to no intervention from a societal perspective. A decision model was developed using, e.g. information on age-specific fatality rates, ICU costs and outcomes, and the herd protection threshold. The net monetary benefit (NMB) was calculated based upon the willingness to pay for new medicines for the treatment of cancer, a condition with a similar disease burden in the near term.

RESULTS

The marginal cost-effectiveness ratio (MCER) of the last bed added to the existing ICU capacity is €21,958 per life-year gained assuming full bed utilization. The NMB decreases with an additional expansion but remains positive for utilization rates as low as 2%. In a sensitivity analysis, the variables with the highest impact on the MCER were the mortality rates in the ICU and after discharge.

CONCLUSIONS

This article demonstrates the applicability of cost-effectiveness analysis to policies of hospital pandemic preparedness and response capacity strengthening. In Germany, the provision of a staffed ICU bed reserve capacity appears to be cost-effective even for a low probability of bed utilization.

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

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

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.

Values for health states with different life durations

BACKGROUND

Recent research suggests that the value of health states may depend on their duration, implying a more complex relationship between quality and quantity of life than the standard linear relationship assumed in the quality-adjusted life years (QALY) model.

OBJECTIVE

This study models how duration affects the value of health states, using discrete choice data.

METHODS

A study was conducted comprising health profiles including various durations. Health states were described with the EQ-5D. Duration was introduced as a sixth domain with six levels (1, 5, 10, 15, 30, 50 years). Sixty pairs of health profiles were selected, applying a Bayesian approach. Two hundred eight university students self-completed the computerized response tasks. Data were analyzed with a conditional logistic regression model.

RESULTS

There is clear evidence for non-linear values for duration, that is, preferences for duration are more accurately described by a logarithmic function.

CONCLUSIONS

In discrete choice experiments using health states with different durations, these data present the first evidence for decreasing marginal utility for duration. Our results suggest that refinement of the standard QALY framework may be needed for states with a long duration.

Maximal endurable time states and the standard gamble: more preference reversals

BACKGROUND

The time trade off (TTO) method is not sensitive to maximal endurable time preferences, as preference reversals occur. The standard gamble (SG) method has not been tested regarding its sensitivity to maximal endurable time preferences.

OBJECTIVE

This study investigates whether preference reversals occur for the SG method as well.

METHODS

Fifty-nine respondents stated for several migraine health states their preference for living 10 or 20 years in that state. A migraine state was selected for which a respondent preferred 10-20 years, a maximal endurable time preference. Two probability equivalent gambles were obtained for the migraine states lasting 10 and 20 years, respectively. Preference reversals occurred when the gamble, equivalent to the longer duration, was preferred to the gamble equivalent to the shorter duration.

RESULTS

Out of 59 respondents, 48 had maximal endurable time preferences. Of these 48 respondents, 34 (71%) showed a preference reversal. This percentage differed significantly from chance, that is 50% (P = 0.004), indicating that preference reversals occurred reliably.

CONCLUSION

The observed reversal rate for the standard gamble is similar to rates observed previously with the TTO method. Utility measurement of poor health states is problematic, both with the TTO and standard gamble methods.

Testing the rate of preference reversal in personal and social decision-making

Classic preference reversal, where choice and valuation procedures generate inconsistent preference orderings, has rarely been tested in hypothetical health care treatment scenarios. Two studies - the first non-incentivised and the second incentivised - are reported in this article. In both studies, respondents are asked to make decisions that affect themselves (a personal decision making frame) and those for whom they are responsible (a social decision making frame). The results show non-negligible and systematic rates of preference reversal in both frames, although these rates are slightly, but non-significantly, lower in the incentivised condition. Moreover, in both studies, the rate of predicted preference reversal was somewhat higher in the social than in the personal decision making frame, a finding that is explained by greater risk aversion when choosing treatment options for others than when choosing treatments for oneself.

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.

Testing procedural invariance in the context of health

Violations of procedural invariance, epitomised by 'classic' preference reversals, have been observed for more than 40 years, and yet the study of this phenomenon in health remains nascent. This is an oversight because such violations pose a challenge to health economics, where choice and valuation methodologies often are used interchangeably. This article reports two experiments that aim to test for preference reversals over outcomes defined by health status, using both 'open' and 'assisted' valuation procedures. Although systematic preference reversals in the direction generally reported in the literature were not observed, the rates of non-systematic reversal were substantial, measuring 35-40%. By analysing the respondents' explanations for their answers, it is clear that many of them used heuristics to answer the questions, and they may have good reasons to do so, which undermines the notion that preferences are always fixed and stable. These results, and others like it, pose a challenge to those who unquestioningly assume procedural invariance and maintain that population preferences should be used to inform health policy.

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

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

A test of independence of discounting from quality of life

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

Using QALYs in cancer: a review of the methodological limitations

The objective of this paper is to examine how well the QALY captures the health gains generated by cancer treatments, with particular focus on the methods for constructing QALYs preferred by the UK National Institute for Health and Clinical Excellence (NICE). Data were obtained using a keyword search of the MEDLINE database and a hand search of articles written by leading researchers in the subject area (with follow up of the references in these articles). Key arguments were discussed and developed at an oncology workshop in September 2009 at the Office of Health Economics. Three key issues emerged. First, the EQ-5D, NICE's preferred measure of health-related quality of life (QOL) in adults, has been found to be relatively insensitive to changes in health status of cancer patients. Second, the time trade-off, NICE's preferred technique for estimating the values of health states, involves making assumptions that are likely to be violated in end-of-life scenarios. Third, the practice of using valuations of members of the general population, as recommended by NICE, is problematic because such individuals typically display a misunderstanding of what it is really like for patients to live with cancer. Because of the way in which it is constructed, the QALY shows important limitations in terms of its ability to accurately capture the value of the health gains deemed important by cancer patients. A research agenda for addressing these limitations is proposed.

A new prize system for drug innovation

We propose a new prize (reward) system for drug innovation which pays a price based on the value of health benefits accrued over time. Willingness to pay for a unit of health benefit is determined based on the cost-effectiveness ratio of palliative/nursing care. We solve the problem of limited information on the value of health benefits by mathematically relating reward size to the uncertainty of information including information on potential drug overuse. The proposed prize system offers optimal incentives to invest in research and development because it rewards the innovator for the social value of drug innovation. The proposal is envisaged as a non-voluntary alternative to the current patent system and reduces excessive marketing of innovators and generic drug producers.

Empirical validation of patient versus population preferences in calculating QALYs

A fundamental assumption of the quality-adjusted life year model is mutual utility independence between life years and health status. However, this assumption may not hold for severe health states: living in a severe health state may cause disutility beyond a so-called maximal endurable time (MET). It is unknown, however, whether persons without experience of a disease, who are often used in health state valuation exercises, account for MET. Using data from 159 respondents from two convenience samples in Germany who were presented a health state description of depression, this study shows that persons without experience of depression had a lower rate of MET than persons with a history of depression. Furthermore, they had more preference reversals in case of MET, thus violating a fundamental principle of rational choice theory. While these findings suggest that severe health states should be assessed by patients rather than the community, confirmation in additional studies outside Germany and based on other health-state valuation techniques and diseases is recommended.

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

Purpose

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

Methods

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

Results

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

Conclusions

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

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

Purpose

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

Methods

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

Results

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

Conclusions

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

Incorporating extrinsic goals into decision and cost-effectiveness analyses

It has not been widely recognized that medical patients as individuals may have goals that are not easily expressed in terms of quality-adjusted life years (QALYs). The QALY model deals with ongoing goals such as reducing pain or maintaining mobility, but goals such as completing an important project or seeing a child graduate from college occur at unique points in time and do not lend themselves to easy expression in terms of QALYs. Such extrinsic goals have been posited as explanations for preferences inconsistent with the QALY model, such as unwillingness to trade away time or accept gambles. In this article, the authors examine methods for including extrinsic goals in medical decision and cost-effectiveness analyses. As illustrations, they revisit 2 previously published analyses, the management of unruptured intracranial arteriovenous malformations (AVMs) and the evaluation of preventive strategies for BRCA + women.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

The gap effect: discontinuities of preferences around dead

BACKGROUND

The assessment of health states considered to be worse than dead is a controversial issue.

OBJECTIVE

To investigate how health states are valued when they are close to dead. Differences between adjacent states are compared with the differences between the first positive/first negative state with death.

METHODS

A secondary analysis of the EuroQol EQ-5D data of the measurement of valuation and health (MVH) study was made. Visual analog scale (VAS) and time trade-off (TTO) preferences for 43 health states were obtained. Various subsets of 13 states were valued by 3395 respondents. States were rank ordered by their VAS and TTO values. Differences between adjacent states were calculated for the VAS and the positive and negative TTO values.

RESULTS

Complete data were obtained in 2997 respondents. The differences between the ordered VAS values were equally large. In contrast, significant gaps around dead were found for the positive as well as the negative TTO values.

DISCUSSION

These results are interpreted in light of a descriptive QALY model. This model was expanded to include utilities worse than dead. The VAS task does not pick up that bad states become intolerable, i.e. worse than dead, when they last too long, but the TTO task does. The current QALY model seems to lack descriptive validity for states valued worse than dead and for states with a maimal endurable time.

The value of life: individual preferences and social choice. A comment to Magnus Johannesson

In order to avoid undue discrimination of disabled people, we have suggested that all life years gained by the disabled should count as 1 in QALY calculations as long as the health states in question are preferred to being dead by those concerned. Johannesson noted that such a convention could lead to inconsistencies between societal and individual preferences. We believe the problem derives from the structure of preferences in the real world, rather than from our specific choice of model. The inconsistency is at any rate a much smaller practical problem than Johannesson suggests. Johannesson's alternative model has some virtues, but it does not resolve the inconsistency problem. It also leads to counter intuitive results.

The validity of time trade-off values in calculating QALYs: constant proportional time trade-off versus the proportional heuristic

In order to calculate quality adjusted life years (QALYs) from time trade-off (TTO) responses, individual preferences are required to satisfy the constant proportional time trade-off (CPTTO) assumption. Respondents who use a simple proportional heuristic may appear to satisfy CPTTO but will in fact generate preference reversals for states that are associated with a maximal endurable time (MET). Using data from 91 respondents, the study reported here examines the extent to which valuations satisfy the CPTTO assumption and the extent to which they might be generated by the proportional heuristic. The results suggest that respondents are using a proportional heuristic that casts doubt on the validity of using the TTO method to calculate QALYs for health states that are associated with MET preferences.