Comparing the performance of the EQ-5D-3L and the EQ-5D-5L in young Portuguese adults

BACKGROUND

Some studies have reported a ceiling effect in EQ-5D-3L, especially in healthy and/or young individuals. Recently, two further levels have been included in its measurement model (EQ-5D-5L). The purposes of this study were (1) to assess the properties of the EQ-5D-5L in comparison with the standard EQ-5D-3L in a sample of young adults, (2) to foreground the importance of collecting qualitative data to confirm, validate or refine the EQ-5D questionnaire items and (3) to raise questions pertaining to the wording in these questionnaire items.

METHODS

The data used came from a sample of respondents aged 30 or under (n = 624). They completed both versions of the EQ-5D, which were compared in terms of feasibility, level of inconsistency and ceiling effect. Agreement between the instruments was assessed using correlation coefficients and Bland-Altman plots. Known-groups validity of the EQ-5D-5L was also assessed using non-parametric tests. The discriminative properties were compared using receiver operating characteristic curves. Finally, four interviews were conducted for retrospective reports to elicit respondents' understanding and perceptions of the format, instructions, items, and responses.

RESULTS

Quantitative results show a ceiling effect reduction of 25.3 % and a high level agreement between both indices. Known-groups validity was confirmed for the EQ-5D-5L. Explorative interviews indicated ambiguity and low degree of certainty in regards to conceptualizing differences between levels moderate-slight across three dimensions.

CONCLUSIONS

The EQ-5D-5L performed better than the EQ-5D-3L. However, the explorative interviews demonstrated several limitations in the EQ-5D questionnaire wording and high context-dependent answers point to lack of illnesses' experience amongst young adults.

SF-6D Portuguese population norms

BACKGROUND

Population-based norms are important because they provide benchmarks that allow the interpretation of subgroups of population health, comparisons between studies, information on health inequalities and support for health-care interventions. The SF-6D is a preference-based measure of health, the use of which has been increasing throughout the world.

OBJECTIVE

Other countries have provided population norms for the SF-6D. To date, SF-6D population norms for Portugal do not exist. This study therefore aimed to derive SF-6D Portuguese population norms.

METHODS

A representative sample of the Portuguese general public (n = 1,500) was used in a telephone-based interview. The SF-36v2 was applied and the Portuguese SF-6D value set was used to obtain the SF-6D index. Descriptive and inferential data analyses were applied to sociodemographic variables, the dimensions of the SF-6D and the SF-6D index. Health index scores of the target population and selected subpopulations were estimated using domain estimation techniques when necessary.

RESULTS

SF-6D utility scores decline with increasing age. Women, widowed individuals and individuals with low educational attainment report lower levels of SF-6D utility scores than men, those with a high educational attainment and those who are single.

CONCLUSIONS

This study reports Portuguese population norms measured using the SF-6D based on a national representative sample. These results can be used as reference data to inform policy.

Comparing the performance of the SF-6D and the EQ-5D in different patient groups

INTRODUCTION

This research aims to explore the performance of the SF-6D and the EQ-5D in patients suffering from asthma, chronic obstructive pulmonary disease, cataracts, and rheumatoid arthritis. In particular, the aim of this research is twofold: 1) to study the level of agreement between the indexes and the descriptive systems of the dimensions of the SF-6D and the EQ-5D, and 2) to analyze the discriminative ability of the instruments.

MATERIAL AND METHODS

A sample of 643 patients completed both the SF-36v2 and the EQ-5D. The discriminative ability of the instruments was analyzed. Furthermore, the level of agreement between the indexes and the descriptive systems of the dimensions of the SF-6D and the EQ-5D were studied. The level of agreement between instruments was investigated using correlation coefficients and the Bland-Altman plots, while the influence of medical condition and other socio-demographic variables was analyzed using nonparametric tests. Paired-samples tests were used to identify differences between the scores.

RESULTS AND DISCUSSION

The results show a strong correlation and agreement between both indexes. Overall, questionnaire indexes differ by medical condition and socio-demographic groups and both instruments are able to discriminate between socio-demographic groups.

CONCLUSION

This study confirmed the hypothesis that the SF-6D generates higher utility values in less healthy individuals. The SF-6D and the EQ-5D seem to perform differently in each of the diseases studied since the descriptive statistics differ between instruments and the level of correlation is not uniform. Results show that the instruments generate different utility values, but there is a strong agreement between both indexes. Thus, the two instruments are not interchangeable and their results cannot be directly comparable.

Exploring the consistency of the SF-6D

OBJECTIVE

The six-dimensional health state short form (SF-6D) was designed to be derived from the short-form 36 health survey (SF-36). The purpose of this research was to compare the SF-6D index values generated from the SF-36 (SF-6DSF-36) with those obtained from the SF-6D administered as an independent instrument (SF-6DInd). The goal was to assess the consistency of respondents' answers to these two methods of deriving the SF-6D.

METHODS

Data were obtained from a sample of the Portuguese population (n = 414). Agreement between the instruments was assessed on the basis of a descriptive system and their indexes. The analysis of the descriptive system was performed by using a global consistency index and an identically classified index. Agreement was also explored by using correlation coefficients. Parametric tests were used to identify differences between the indexes. Regression models were estimated to understand the relationship between them.

RESULTS

The SF-6DInd generates higher values than does the SF-6DSF-36. There were significant differences between the indexes across sociodemographic groups. There was a significant ceiling effect in the SF-6DInd but not in the SF-6DSF-36. The correlation between the indexes was high but less than what was anticipated. The global consistency index identified the dimensions with larger differences. Considerable differences were found in two dimensions, possibly as a result of different item contexts. Further research is needed to fully understand the role of the different layouts and the length of the questionnaires in the respondents' answers.

CONCLUSIONS

The results show that as the SF-6D was designed to derive utilities from the SF-36 it should be used in this way and not as an independent instrument.

EQ-5D Portuguese population norms

OBJECTIVES

The EQ-5D is a widely used preference-based measure. Normative data can be used as references to analyze the effects of healthcare, determine the burden of disease and enable regional or country comparisons. Population norms for the EQ-5D exist for other countries but have not been previously published for Portugal. The purpose of this study was to derive EQ-5D Portuguese population norms.

METHODS

The EQ-5D was applied by phone interview to a random sample of the Portuguese general population (n = 1,500) stratified by age, gender and region. The Portuguese value set was used to derive the EQ-5D index.

RESULTS

Mean values were computed by gender and age groups, marital status, educational attainment, region and other variables to obtain the EQ-5D Portuguese norms. Health status declines with advancing age, and women reported worse health status than men. These results are similar to other EQ-5D population health studies.

CONCLUSION

This study provides Portuguese population health-related quality of life data measured by the EQ-5D that can be used as population norms. These norms can be used to inform Portuguese policy makers, health care professionals and researchers in issues related to health care policy and planning and quantification of treatment effects on health status.

The valuation of the EQ-5D in Portugal

PURPOSE

The EQ-5D is a preference-based measure widely used in cost-utility analysis (CUA). Several countries have conducted surveys to derive value sets, but this was not the case for Portugal. The purpose of this study was to estimate a value set for the EQ-5D for Portugal using the time trade-off (TTO).

METHODS

A representative sample of the Portuguese general population (n = 450) stratified by age and gender valued 24 health states. Face-to-face interviews were conducted by trained interviewers. Each respondent ranked and valued seven health states using the TTO. Several models were estimated at both the individual and aggregated levels to predict health state valuations. Alternative functional forms were considered to account for the skewed distribution of these valuations.

RESULTS

The models were analyzed in terms of their coefficients, overall fit and the ability for predicting the TTO values. Random effects models were estimated using generalized least squares and were robust across model specification. The results are generally consistent with other value sets.

CONCLUSION

This research provides the Portuguese EQ-5D value set based on the preferences of the Portuguese general population as measured by the TTO. This value set is recommended for use in CUA conducted in Portugal.

A Portuguese value set for the SF-6D

OBJECTIVES

The SF-6D is a preference-based measure of health derived from the SF-36 that can be used for cost-effectiveness analysis using cost-per-quality adjusted life-year analysis. This study seeks to estimate a system weight for the SF-6D for Portugal and to compare the results with the UK system weights.

METHODS

A sample of 55 health states defined by the SF-6D has been valued by a representative random sample of the Portuguese population, stratified by sex and age (n = 140), using the Standard Gamble (SG). Several models are estimated at both the individual and aggregate levels for predicting health-state valuations. Models with main effects, with interaction effects and with the constant forced to unity are presented. Random effects (RE) models are estimated using generalized least squares (GLS) regressions. Generalized estimation equations (GEE) are used to estimate RE models with the constant forced to unity. Estimations at the individual level were performed using 630 health-state valuations. Alternative functional forms are considered to account for the skewed distribution of health-state valuations.

RESULTS

The models are analyzed in terms of their coefficients, overall fit, and the ability for predicting the SG-values. The RE models estimated using GLS and through GEE produce significant coefficients, which are robust across model specification. However, there are concerns regarding some inconsistent estimates, and so parsimonious consistent models were estimated. There is evidence of under prediction in some states assigned to poor health. The results are consistent with the UK results.

CONCLUSION

The models estimated provide preference-based quality of life weights for the Portuguese population when health status data have been collected using the SF-36. Although the sample was randomly drowned findings should be treated with caution, given the small sample size, even knowing that they have been estimated at the individual level.

How consistent are health utility values?

The use of preference-based generic instruments to measure the health-related quality of life of a general population or of individuals suffering from a specific disease has been increasing. However, there are several discrepancies between instruments in terms of utility results. This study compares SF-6D and EQ-5D when administered to patients with cataracts and aims at explaining the differences. Agreement between EQ-5D and SF-6D health state classifications was assessed by correlation coefficients. Simple correspondence analysis was used to assess the agreement among the instrument's descriptive systems and to investigate similarities between dimensions' levels. Cluster analysis was used to classify SF-6D and EQ-5D levels into homogeneous groups. There was evidence of floor effects in SF-6D and ceiling effects in EQ-5D. Comparisons of means showed that SF-6D values exceeded EQ-5D values. Agreement between both instruments was high, especially between similar dimensions. However, different valuation methods and scoring algorithms contributed to the main differences found. We suggest that one or both instruments should be revised, in terms of their descriptive systems or their scoring algorithms, in order to overcome the weakness found.