Title: Valuing health states: interviews with the general public
Authors: Gudex, Claire and Dolan, Paul and Kind, Paul and Thomas, Roger and Williams, Alan
Publisher: The European journal of public health, 7 (4). pp. 441-448
Abstract: The objective of this study was to develop methods to elicit the general public’s views on the comparative subjective value of different states of health. The resulting valuations form the basis for a set of British social preferences for use in clinical and economic evaluation of health care. The methods have proved extremely successful in generating complete data of high quality. Since the approach used is generally applicable for use in other national surveys, it is described here to encourage others to take the opportunity to generate comparable sets of social preferences. Face to face interviews, lasting approximately 1h, were conducted in the respondents’ own homes. There were 3, 395 interviews achieved (a response rate of 64%) and the sample was representative of the British general population in terms of age, sex, education, social class and geographical location. Each respondent valued 15 EuroQol health states using ranking, visual analogue scale (VAS) and time trade-off (TTO) methods, with 45 states being valued in all. Two hundred and twenty-one reinterviews were conducted after an average time of 10 weeks. Several methodological issues had to be confronted during the course of the study. These included the structure and format of the interview, the choice of health states to be valued, the determination of the sample size required, the achievement of a representative sample of the British adult population, interviewer training, data processing and data quality. Since few valuation studies have been undertaken on such a large scale, much time and effort was spent in resolving these issues. The methods used are recommended to others considering similar surveys.
Title: The time trade-off: a note on lifetime reallocation of consumption and discounting
Authors: Dolan, Paul and Jones-Lee, Michael
Publisher: Journal of health economics, 16 (6). pp. 731-739
Abstract: This paper considers the extent to which responses to time trade-off (TTO) questions can provide unbiased estimates of ratios of individual marginal rates of substitution (MRS) of wealth for risk of various health state impairments relative to the corresponding MRS for risk of death. It is shown that if there is reallocation of lifetime consumption and/or discounting of future utilities, then a TTO response that is not adjusted for these effects will unambiguously overestimate the ratios of individual MRS. While the effect of reallocation is likely to be very small, discounting can lead to significant overestimation, the magnitude of which depends in part upon the severity of the health state impairment.
Title: Modelling valuations for health states
Authors: Dolan, Paul
Publisher: Medical care, 35 (11). pp. 1095-1108
Abstract: OBJECTIVES: It has become increasingly common for preference-based measures of health-related quality of life to be used in the evaluation of different health-care interventions. For one such measure, The EuroQol, designed to be used for these purposes, it was necessary to derive a single index value for each of the 243 health states it generates. The problem was that it was virtually impossible to generate direct valuations for all of these states, and thus it was necessary to find a procedure that allows the valuations of all EuroQol states to be interpolated from direct valuations on a subset of these. METHODS: In a recent study, direct valuations were elicited for 42 EuroQol health states (using the time trade-off method) from a representative sample of the UK population. This article reports on the methodology that was adopted to build up a “tariff” of EuroQol values from this data. RESULTS: A parsimonious model that fits the data well was defined as one in which valuations were explained in terms of the level of severity associated with each dimension, an intercept associated with any move away from full health, and a term that picked up whether any dimension in the state was at its most severe level. CONCLUSIONS: The model presented in this article appears to predict the values of the states for which there are direct observations and, thus, can be used to interpolate values for the states for which no direct observations exist.
Title: Valuing health states using VAS and TTO: what lies behind the numbers?
Authors: Robinson, Angela and Dolan, Paul and Williams, Alan
Publisher: Social science & medicine, 45 (8). pp. 1289-1297
Abstract: It is well known that different methods of eliciting the valuations attached to various health states, such as the Visual Analogue Scale (VAS) and the Time Trade Off (TTO), yield different results. This study gathers qualitative data from a group of 43 respondents who had previously taken part in a large scale national study which set out to elicit the values attached by individuals to various health states using both the VAS and the TTO techniques. The findings of this study raised three questions which are of particular interest here: (1) Why are some states that are rated better than dead on the VAS often rated as worse than dead in TTO? (2) Why are some respondents unwilling to trade off any time at all in order to avoid a health state that they place below full health on the VAS? (3) Why are TTO valuations of older respondents for the more severe health states lower than those of the younger age groups? This study has uncovered qualitative evidence on each of these three key issues. Regarding the first question, many respondents did not appear to interpret a better than dead VAS score as a strict preference for spending 10 years in a health state over immediate death. Several different factors appeared to contribute towards this, an important one being the tendency of respondents to ignore the duration of the health state during the VAS task. Regarding the second question, there is evidence of the existence of a “threshold of tolerability” below which states would have to fall before some respondents would be willing to give up any time at all on the TTO. Regarding the last question, it appears that older respondents are less likely to find the worse than dead TTO scenario plausible than those in the younger age groups. However, whilst this may explain why older respondents attach lower worse than dead valuations to health states, it does not appear to account for the entire difference in TTO valuations between the two age groups. In addition, it appears that older respondents may be less prepared to live for the next 10 years in a diminished health state.
Title: Aggregating health state valuations
Author: Dolan, Paul
Publisher: Journal of health services research and policy, 2 (3). pp. 166-167
Abstract: It is now recognized that preference-based measures of health status have an important role to play in determining priorities in health care. A number of methodological and ethical issues have been raised, but one that has as yet received little attention is the question of how individual responses should be aggregated when attempting to express the valuations of a given group. In a recent study of over 3000 members of the British general public, valuations were elicited for health states defined in terms of the EuroQol Descriptive System using the time trade-off method. A EuroQol ‘tariff’ of valuations has been generated which, because of the methodology employed, provides a good approximation of mean values. The purpose of this paper is to present a tariff based on median values. The nature of the distributions of values results in a median-based tariff which, compared to the mean-based one, has higher values for less severe states and lower values for more severe states. This is likely to have important implications for resource allocation decisions.
Title: Quality of life analysis in patients with lower limb ischaemia: suggestions for European standardisation
Authors: Chetter, I. C. and Spark, J. and Dolan, Paul and Scott, D. J. A. and Kester, R. C.
Publisher: European journal of vascular and endovascular surgery, 13 (6). pp. 597-604
Abstract: Introduction and Objectives: In this era of evidence-based medicine and limited resources we seem obliged, on clinical and economic grounds, to demonstrate that we improve not only patient survival but also the quality of patients’ lives. This study aims to determine the impact of increasing lower limb ischaemia on quality of life (QOL) and which of three commonly used generic QOL instruments is the most valid, reliable, and responsive to change in patients with lower limb ischaemia. Patients and Methods: Two hundred and thirty-five patients, 144 men and 91 women, median age 68 years (range 41–87 years) were graded according to ISCVS suggested reporting standards, i.e. 16 mild, 116 moderate and 25 severe claudicants; 33 patients had rest pain and 45 tissue loss. Patients completed Short Form 36 (SF36), EuroQol (EQ-5D) and Nottingham Health Profile (NHP) questionnaires at interview. Additional copies of questionnaires were posted to 80 patients prior to attendance. Correlation between the two sets of responses reflects test-retest reliability. Correlation between domains measured by the three instruments reflects convergent and divergent validity. Kruskal Wallis ANOVA detected QOL changes across the whole group. Spearman Rank was used to analyse validity and reliability. Responsiveness was analysed using the Mann-Whitney U-test. Results: Increasing lower limb ischaemia confers significant (p<0.05) deterioration in: SF36 measured: physical functioning, physical role, pain, general health, vitality, social functioning and mental health. EQ-5D measured: mobility, self-care, usual activities, pain and anxiety/depression. NHP measured: energy, pain, emotional reaction, sleep, social isolation and physical mobility. All three instruments are significantly reliable (rs>0.7). The validity of SF36 and NHP (rs=0.68–0.78) is superior to EQ-5D (rs=0.37–0.7). SF36 & NHP are equally responsive to changes in physical activity and pain. SF36 and EQ-5D are most responsive to changes in social activity. SF36 is most responsive to changes in psychological status. Conclusion: QOL deteriorates markedly with increasing lower limb ischaemia. The SF36 would appear to be the most appropriate generic QOL analysis tool for these patients. We recommend its widespread adoption throughout Europe, thus providing a standardised tool for reporting generic QOL.
Title: Mapping visual analogue scale health state valuations onto standard gamble and time trade-off values
Authors: Dolan, Paul and Sutton, M.
Publisher: Social science & medicine, 44 (10). pp. 1519-1530
Abstract: Despite becoming increasingly common in evaluations of health care, different methods of quantitatively measuring health status appear to produce different valuations for identical descriptions of health. This paper reports on a study that elicited health state valuations from the general public using three different methods: the visual analogue scale (VAS), the standard gamble (SG) and the time trade-off (TTO). Two variants of the SG and TTO were tested: Props (using specially designed boards and cards); and No Props (using a self-completion booklet). This paper focuses on empirical relationships between health state valuations from the VAS and the (four) other methods. The relationships were estimated using Tobit regression of individual-level data. In contrast to a priori expectations, the mapping functions estimated suggest that differences are more pronounced across variant than across method. Furthermore, relationships with VAS scores are found to depend on the severity of the state: TTO Props valuations are higher than VAS responses for mild states and lower for more severe states; SG Props valuations are broadly similar to VAS scores over a wide range; and No Props responses are consistently higher than VAS valuations, particularly for more severe states. Explanations are proposed for these findings.
Title: The nature of individual preferences: a prologue to Johannesson, Jonsson and Karlsson
Authors: Dolan, Paul
Publisher: Health economics, 6 (1). pp. 91-93
Title: Correlating clinical indicators of lower-limb ischaemia with quality of life
Authors: Chetter, I. C. and Dolan, Paul and Spark, J. and Scott, D. J. A. and Kester, R. C.
Publisher: Cardiovascular surgery, 5 (4). pp. 361-366.
Abstract: The objectives of the study were to analyse the impact of increasing lower-limb ischaemia upon quality of life and to assess the correlation between clinical indicators of lower-limb ischaemia and such quality. A prospective observational study of a consecutive series of 235 patients (144 men and 91 women; median age 68 (range 41-87) years presenting with varying degrees of lower-limb ischaemia graded according to ISCVS criteria was performed. Data was collected at interview before any intervention. Clinical indicators of lower-limb perfusion included: intermittent claudication and maximum walking distance on standardized treadmill testing; ankle:brachial pressure indices and isotope limb blood flow. Quality of life analysis was performed using the EuroQol (EQ) questionnaire. This is a standardized generic instrument for describing health-related quality of life and consists of a descriptive system of five dimensions, each measured on three levels. Thus, a profile and two single indices of quality of life were derived using different methods. Increasing lower-limb ischaemia results in a statistically significant deterioration in both global quality of life and in all EQ-measured quality of life dimensions (P < 0.01 Kruskal-Wallis, ANOVA). The correlation between clinical indicators and quality of life is statistically significant but not sufficiently close (correlation coefficients < 0.6) to assume that variations in clinical indicators result in reciprocal variations in quality of life. In conclusion, as might be expected, a significant correlation exists between clinical indicators of lower-limb ischaemia and health-related quality of life. However, the low correlation coefficients emphasize how tenuous the association is. Thus, a significant improvement in the clinical indicators of lower-limb ischaemia cannot be assumed to impart a similar benefit on quality of life. The latter concept must therefore be analysed independently.