Minimally Important Difference of the EQ-5D-5L Index Score in Adults with Type 2 Diabetes.

BACKGROUND: The EuroQol five-dimensional questionnaire (EQ-5D) is a generic preference-based measure of health-related quality of life, and several studies have made attempts to estimate the minimally important difference (MID) for the EQ-5D index score. OBJECTIVES: To estimate the MID of the five-level EQ-5D (EQ-5D-5L) index score in a population-based sample of adults with type 2 diabetes and to explore whether the MID estimate varies by baseline index score and the direction of change in health status. METHODS: We used longitudinal survey data of adults with type 2 diabetes in Alberta, Canada. The EQ-5D-5L MID was estimated first by the instrument-defined approach, which used the difference between the baseline index scores and the index scores of simulated single-level transitions, and then by the anchor-based approach, which categorized 1-year changes in depressive symptoms, diabetes-related distress, as well as physical and mental health functioning into no change, small change, and large change groups, wherein the MID was estimated as the average change in index score of the small change group. RESULTS: Using the instrument-defined approach, MID estimates were 0.043, 0.040, and 0.045, whereas anchor-based MID estimates were 0.042, 0.034, and 0.049 for all change, improvement, and deterioration, respectively. Larger MID estimates were observed for lower baseline index scores and for deterioration in health status. CONCLUSIONS: MID estimates of the EQ-5D-5L index score were consistent between instrument-defined and anchor-based approaches and ranged between 0.03 and 0.05. Estimates varied by baseline index score and the direction of change, with similar results for patient subgroups.

Instrument-Defined Estimates of the Minimally Important Difference for EQ-5D-5L Index Scores.

BACKGROUND: The five-level EuroQol five-dimensional questionnaire (EQ-5D-5L) is a preference-based measure of health-related quality of life (HRQOL), which yields an index score anchored at 0 (dead) and 1 (full health). We lack evidence on estimates for the minimally important difference (MID) of the EQ-5D-5L that will help in interpreting differences or changes in HRQOL measured by this scale score. OBJECTIVES: To estimate the MID of the EQ-5D-5L index score for available scoring algorithms including algorithms from Canada, China, Spain, Japan, England, and Uruguay. METHODS: A simulation-based approach based on instrument-defined single-level transitions was used to estimate the MID values of the EQ-5D-5L for each country-specific scoring algorithm. RESULTS: The simulation-based instrument-defined MID estimates (mean ± SD) for each country-specific scoring algorithm were as follows: Canada, 0.056 ± 0.011; China, 0.069 ± 0.007; Spain, 0.061 ± 0.008; Japan, 0.048 ± 0.004; England, 0.063 ± 0.013; and Uruguay, 0.063 ± 0.019. Differences in MID estimates reflect differences in population preferences, in valuation techniques used, as well as in modeling strategies. After excluding the maximum-valued scoring parameters, the MID estimates (mean ± SD) were as follows: Canada, 0.037 ± 0.001; China, 0.058 ± 0.005; Spain, 0.045 ± 0.009; Japan, 0.044 ± 0.004; England, 0.037 ± 0.008; and Uruguay, 0.040 ± 0.010. CONCLUSIONS: Simulation-based estimates of the MID of the EQ-5D-5L index score were generally between 0.037 and 0.069, which are similar to the MID estimates of other preference-based HRQOL measures.

Comparative performance of the EQ-5D-5L and SF-6D index scores in adults with type 2 diabetes.

PURPOSE: To explore the comparative performance including discriminative and longitudinal validity of EQ-5D-5L and SF-6D index scores in adults with type 2 diabetes. METHODS: Data from an on-going cohort study of adults with type 2 diabetes in Alberta, Canada, were used. Known-groups approach was used to examine discriminative validity. Correlation and agreement indices and scatter and Bland-Altman plots were used to examine the relationship between the two measures. Longitudinal validity was explored using Wilcoxon signed-rank test, effect size, and standardized response mean. RESULTS: In 1832 participants at baseline (age 64.3, standard deviation 10.6 years; 45% female), median EQ-5D-5L score was 0.85 [interquartile range (IQR) 0.17], and floor and ceiling effects of 0.1 and 16.1%, respectively; median SF-6D score was 0.72 (IQR 0.24), and floor and ceiling effects of 0.1 and 3.2%, respectively. EQ-5D-5L and SF-6D index scores were significantly correlated with an overall Spearman correlation coefficient of 0.73, and an ICC of 0.62 (95% CI 0.42-0.74). Both EQ-5D-5L and SF-6D scores demonstrated statistically significant differences in self-reported chronic conditions, depressive symptoms, and diabetes-related distress, and were able to detect changes in depressive symptoms and diabetes distress across all change groups. CONCLUSIONS: Both EQ-5D-5L and SF-6D index scores provide valid measurement in this patient population. Considerable overlap between the measures means it is not necessary to include both in surveys, however, the advantages and disadvantages of each should be considered.

Health literacy and health-related quality of life in adults with type 2 diabetes: a longitudinal study.

PURPOSE: To examine the association of health literacy (HL) with changes in health-related quality of life (HRQL) among patients with type 2 diabetes. METHODS: Data from a cohort study of type 2 diabetes patients were used. HL was assessed using 3 previously validated screening questions and HRQL using the EQ-5D-5L and SF-12 [physical and mental composite summary scores (PCS, MCS)]. The associations of baseline HL with changes in EQ-5D, PCS, and MCS scores over 1 year and with directions of changes (no change; declined; improved) were examined. Missing data were handled with multiple imputation and sensitivity analyses. RESULTS: Average age of participants (N = 1948) was 64.6 ± 10.9 years, 45 % were female, and 12.6 % had inadequate HL. Participants had mean decrements of 0.01 in EQ-5D, 1.0 in PCS, and 1.2 in MCS over 1 year. In adjusted analysis, HL was not associated with changes in EQ-5D over 1 year (ß = 0.01, P = 0.146); however, patients with adequate HL had 2.1 points greater increase in PCS (P < 0.001) and 3.1 points in MCS (P < 0.001) compared to those with inadequate HL. Patients with adequate HL were less likely to have a decline in EQ-5D (RR 0.66; 95 % CI 0.44, 0.98), PCS (RR 0.51; 95 % CI 0.34, 0.76), and MCS (RR 0.49; 95 % CI 0.33, 0.72) compared to those with inadequate HL. Patients with adequate HL were more likely to have an improvement in MCS compared to those with inadequate HL (RR 1.78; 95 % CI 1.04, 3.04); such associations were not observed for PCS or EQ-5D. All results were robust in sensitivity analyses. CONCLUSIONS: Inadequate HL was independently associated with worsening HRQL in adults with type 2 diabetes, particularly in the mental health domain.

Determinants of time trade-off valuations for EQ-5D-5L health states: data from the Canadian EQ-5D-5L valuation study.

BACKGROUND: Previous studies suggest that population subgroups have different perceptions of health, as well as different preferences for hypothetical health states. OBJECTIVE: To identify determinants of health states preferences elicited using time trade-off (TTO) for the 5-level EQ-5D questionnaire (EQ-5D-5L) in Canada. METHODS: Data were from the Canadian EQ-5D-5L Valuation Study, which took place in Edmonton, Hamilton, Montreal, and Vancouver. Each respondent valued 10 of 86 hypothetical health states during an in-person interview using a computer-based TTO exercise. The TTO scores were the dependent variable and explanatory variables including age, sex, marital status, education, employment, annual household income, ethnicity, country of birth, dwelling, study site, health literacy, number of chronic conditions, previous experience with illness, and self-rated health. RESULTS: Average [standard deviation (SD)] age of respondents (N = 1209) was 48 (17) years, and 45 % were male. In multivariable linear regression models with random effects, adjusted for severity of health states and inconsistencies in valuations, older age [unstandardized regression coefficient (ß) = -0.077], male sex (ß = 0.042), being married (ß = 0.069), and urban dwelling (ß = -0.055) were significantly associated with health states scores. Additionally, participants from Edmonton (ß = -0.124) and Vancouver (ß = -0.156), but not those from Hamilton, had significantly lower TTO scores than those from Montreal. CONCLUSIONS: Socio-demographic characteristics were the main determinants of preferences for EQ-5D-5L health states in this study. Interestingly, preferences were significantly lower in western Canadian cities compared to eastern ones, bringing into question whether a single preference algorithm is suitable for use in all parts of Canada.

Population-level response shift: novel implications for research.

OBJECTIVES: Response shift is a change in perceived HRQL that occurs as a result of recalibration, reprioritization, or reconceptualization of an individual respondent's internal standards, values, or conceptualization of HRQL. In this commentary, we suggest that response shift may also occur at the population level, triggered by causes that affect the distribution of individual-level risk. METHODS: We illustrated the nature and consequences of potential population-level response shift with two examples: the September 11 terror attacks, and the recent denormalization of smoking. RESULTS: Response shift may occur at the population-level, when a large proportion of the population experiences the shift simultaneously, as a unit, and when the cause of the response shift is a socially significant event or trend. Such catalysts are of a qualitatively different nature than the causes leading to health status changes among individuals, and speak to the determinants affecting the underlying distribution of risk in the population. CONCLUSIONS: We do not know if population-level causes have actually resulted in response shifts. Nonetheless, response shifts at the population-level may be worthwhile to investigate further, both to assess the validity of research evidence based on the measurement of HRQL in large populations, and as a desirable intermediate outcome in evaluations of population health programs.

Physical Activity and Health-Related Quality of Life in Adults With Type 2 Diabetes: Results From a Prospective Cohort Study.

BACKGROUND: The objective was to investigate the longitudinal relationship between physical activity and health-related quality of life (HRQL) in adults with type 2 diabetes. METHODS: Data were from a prospective cohort of adults with type 2 diabetes. Weekly moderate-to-vigorous physical activity (MVPA) was reported using the Godin Leisure-Time Physical Activity Questionnaire, and HRQL was reported using the SF-12 and 5-level EQ-5D. Participants were categorized based on current weekly MVPA recommendations. Multivariable linear regression was used to explore associations between MVPA and HRQL, and multinomial logistic regression was used to assess the direction of change in HRQL after 1 year. RESULTS: Mean age of participants (N = 1948) was 64.5 ± 10.8 years and 45% were female. Participants reported a mean of 84.1 ± 172.4 min of MVPA/week, and 21% (n = 416) met weekly MVPA recommendations. MVPA was associated with differences in the physical functioning (b = 5.42; P < .001), general health (b = 2.45; P = .037), and vitality (b = 2.83; P = .016) SF-12 dimensions. Participants who met recommendations were less likely to report a decline (vs. no change) in EQ-5D index score (OR = 0.75; 95% CI [0.57, 0.99]), and SF-12 physical component summary (OR = 0.67; 95% CI [0.50, 0.90]), compared with participants not meeting recommendations. CONCLUSIONS: Participants who met weekly MVPA recommendations reported better physical functioning and were more likely to maintain their physical and overall HRQL over time.