Types of inconsistency in health-state utility judgments

Logical Inconsistencies in 3 Preference Elicitation Methods for EQ-5D Health States: A Study in the Brazilian Population

BACKGROUND

. Logical inconsistency for health states preferences occurs when one logically worse health state, in terms of quality of life, is ranked higher than a logically better health state.

OBJECTIVE

. This study explores the presence of inconsistent responses for the EQ-5D health states valuations in a Brazilian population survey. It compares the level of inconsistency in 3 preference-based methods: ranking, visual analog scale (VAS), and time tradeoff (TTO). The influence of EQ-5D health state descriptions is explored by examining the distance between states using a city-block metric as an indicator of proximity. Moreover, it examines the association between formal education and the presence of inconsistencies, as well as the effect of removing inconsistent respondents on the estimation of social value sets from TTO and VAS.

METHODS

. Data came from a valuation study with 3362 literate individuals aged between 18 and 64 years living in urban areas of Minas Gerais state, Brazil. Logical inconsistency was assessed using the percentage of inconsistent respondents and inconsistency rate. A logistic model was estimated to assess the association between formal education and the logical inconsistency. Societal preferences were estimated excluding inconsistent respondents considering city-block metric.

RESULTS

. The percentage of inconsistent respondents and inconsistency rate are similar for TTO and ranking and lower for VAS. The probability of being inconsistent is higher among less educated groups in ranking and TTO. Inconsistency decreases with distance for all 3 methods. The removal of inconsistent individuals by considering city-block distance improves TTO estimation of social value sets.

CONCLUSION

. Findings suggest that removal of inconsistencies in TTO should consider city-block distance. For VAS, inconsistencies are not associated with formal education and do not affect social value set estimation.

When are person tradeoffs valid?

The person tradeoff (PTO) is commonly used in health economic applications. However, to date it has no theoretical basis. The purpose of this paper is to provide this basis from a set of assumptions that together justify the most common applications of the PTO method. Our analysis identifies the central assumptions in PTO measurements. We test these assumptions in an experiment, but find only limited support for the validity of the PTO.

A pilot Internet "value of health" panel: recruitment, participation and compliance

OBJECTIVES

To pilot using a panel of members of the public to provide preference data via the Internet

METHODS

A stratified random sample of members of the general public was recruited and familiarized with the standard gamble procedure using an Internet based tool. Health states were periodically presented in "sets" corresponding to different conditions, during the study. The following were described: Recruitment (proportion of people approached who were trained); Participation (a) the proportion of people trained who provided any preferences and (b) the proportion of panel members who contributed to each "set" of values; and Compliance (the proportion, per participant, of preference tasks which were completed). The influence of covariates on these outcomes was investigated using univariate and multivariate analyses.

RESULTS

A panel of 112 people was recruited. 23% of those approached (n = 5,320) responded to the invitation, and 24% of respondents (n = 1,215) were willing to participate (net = 5.5%). However, eventual recruitment rates, following training, were low (2.1% of those approached). Recruitment from areas of high socioeconomic deprivation and among ethnic minority communities was low. Eighteen sets of health state descriptions were considered over 14 months. 74% of panel members carried out at least one valuation task. People from areas of higher socioeconomic deprivation and unmarried people were less likely to participate. An average of 41% of panel members expressed preferences on each set of descriptions. Compliance ranged from 3% to 100%.

CONCLUSION

It is feasible to establish a panel of members of the general public to express preferences on a wide range of health state descriptions using the Internet, although differential recruitment and attrition are important challenges. Particular attention to recruitment and retention in areas of high socioeconomic deprivation and among ethnic minority communities is necessary. Nevertheless, the panel approach to preference measurement using the Internet offers the potential to provide specific utility data in a responsive manner for use in economic evaluations and to address some of the outstanding methodological uncertainties in this field.

Person tradeoffs and the problem of risk

Recently, the person tradeoff method has received much attention because it directs one to value health improvements of those other than one's self. As a result, several researchers have suggested that the person tradeoff measures preferences in pharmaceutical and health economic analysis more accurately than the standard gamble, which many consider the gold standard approach. However, the person tradeoff exercise as it is currently practiced assumes a riskless world where policy decisions lead to certain societal outcomes. In reality, health policy decisions are made under risk or uncertainty. Evidence suggests riskless and risky values differ for health improvements over persons. A problem with using the riskless person tradeoff method in economic evaluation of health is that the method conflates a change in the objects of measurement (i.e., a change from health gains with respect to self to gains with respect to others) with a change in the measurement context (i.e., a change from a risk context to a risk-free one). Therefore, it is wise to examine what is sacrificed by ignoring risk and uncertainty inherent in health policy decision making. Given that the choices we make in the context of risk are often different than those we make under certainty, the authors argue that if one assumes context is important, the measurement of health improvements over persons should then be carried out in the context of risk. The authors propose the application of standard methods from utility theory to carry out elicitations for valuing health improvements of others within the context of risky choices. In addition, an alternative perspective of utility is discussed that in comparison puts forth a context free notion of utility.

The validity of person tradeoff measurements: randomized trial of computer elicitation versus face-to-face interview

Can person tradeoff (PTO) value judgments be elicited by a computer, or is a face-to-face interview needed? The authors randomly assigned 95 subjects to interview or computer methods for the PTO, a valuation measure that is often difficult for subjects. They measured relative values of foot numbness, leg paralysis, and quadriplegia (all 3 pairs) at 2 reference group sizes (10 or 100). Relative values did not differ between computer and interview. Overall, 21% of responses were equality responses, 13% were high extreme values, and 5% violated ordinal criteria. The groups did not differ in these measures. The authors also assessed consistency across reference group size (10 v. 100). Although relative values were significantly lower for 100 than for 10, mode did not influence the size of this effect. Subjects made, on average, equally consistent judgments for the 3 comparisons. A computerized PTO elicitation protocol produced results of similar quality to that of a face-to-face interview.