Exploration of a cultural-adaptation of the EQ-5D for Thai population: A “bolt-on” experiment

Development and Testing of the Psychometric Properties of 20 Bolt-On Items for the EQ-5D-5L Across 31 Rare Diseases

OBJECTIVES

Our objective was to develop and assess the psychometric properties of relevant bolt-on items for the EQ-5D-5L in patients with rare diseases (RDs).

METHODS

Nineteen new EQ-5D-5L bolt-ons were developed based on literature review, expert input, and qualitative interviews and focus groups with patients, caregivers, and representatives of patient associations. A nationwide, cross-sectional, web-based survey in China included patients or caregivers of patients with 31 RDs in China (n = 9190). In each RDs, participants completed the EQ-5D-5L and 3 of 20 (1 existing and 19 newly developed) bolt-ons. Ceiling, explanatory power, convergent, divergent, and known-group validity were examined.

RESULTS

Among the bolt-ons, itching had the lowest ceiling (6.5%), whereas social relationships had the highest (42.2%). The absolute reduction in the ceiling of the EQ-5D-5L with the addition of any bolt-ons was limited, ranging from 0 (respiratory problems) to 8.3% points (isolation). Dignity and vitality resulted in the largest increase in explained variance in EQ VAS. The isolation, fertility, and visual acuity bolt-ons showed good divergent validity from the EQ-5D-5L items. There was strong convergent validity between SF-12 and conceptually related bolt-ons (eg, physical health composite and muscle problems bolt-on). Various bolt-ons improved the known-groups validity in specific patient groups, eg, Huntington's disease (oral expressions), scleroderma (dexterity), myasthenia gravis (muscle problems), neuromyelitis optica and multiple sclerosis (fatigue), Marfan syndrome (self-image), and Pompe disease (safety).

CONCLUSION

The EQ-5D-5L shows sufficient validity in most RDs, but incorporating relevant, specific bolt-ons could enhance its ability to more comprehensively assess health-related quality of life in these patients.

Testing the Psychometric Properties of 9 Bolt-Ons for the EQ-5D-5L in a General Population Sample

OBJECTIVES

We aimed to assess the psychometric performance and added value of 9 existing bolt-ons (breathing problems, cognition, hearing, self-confidence, skin irritation, sleep, social relationships, tiredness, and vision) for the EQ-5D-5L in a general population sample.

METHODS

The EQ-5D-5L, 9 bolt-ons, SF-6Dv1, Patient-Reported Outcomes Measurement Information System (PROMIS)-29+2, PROMIS Global Health, and Satisfaction with Life Scale were completed in an online cross-sectional survey among a general adult population sample in Hungary (n = 1587). The following psychometric properties were tested for the EQ-5D-5L + bolt-on(s): ceiling, divergent and convergent validity, structural validity, known-group validity, and explanatory power.

RESULTS

Adding sleep (30%), tiredness (24%), or vision (21%) substantially reduced the ceiling of the EQ-5D-5L (41%). Cognition, sleep, social relationships, and tiredness correlated with corresponding PROMIS and SF-6D items (rs = ǀ0.32ǀ - ǀ0.73ǀ). All bolt-ons, except cognition and self-confidence, loaded on a different factor from the EQ-5D-5L dimensions. Breathing, hearing, skin irritation, and vision significantly improved known-group validity in relevant health condition groups. The sleep bolt-on improved known-group validity in 9 of 13 chronic health conditions. Tiredness had the largest impact on explaining EQ VAS score variance in 8 of 13 conditions. Hearing and vision improved the ability of the EQ-5D-5L to capture declining health with age, whereas self-confidence and social relationships were valuable for mental health assessment.

CONCLUSIONS

This study established the validity of multiple bolt-ons for the EQ-5D-5L and highlights the usefulness of including relevant bolt-ons in population-based and patient surveys. Our findings inform the further development of these bolt-ons and the bolt-on item selection for clinical studies.

Exploring potential EQ-5D bolt-on dimensions with a qualitative approach: an interview study in Hong Kong SAR, China

PURPOSE

The introduction of bolt-on dimensions in EQ-5D instruments is growing common, but most bolt-on studies have targeted the diseased population and obtained bolt-on from other existing Health-related Quality of Life (HRQoL) instruments. As the qualitative approach offers important evidence to support the consistency and design of the potential bolt-on items, this paper studies the Hong Kong SAR community's perception of the current EQ-5D-5 L instrument and identifies potential bolt-on via a qualitative approach.

METHODS

A representative sample mix was recruited based on the age group, gender, and education level composition of the Hong Kong SAR community by quota sampling. Semi-structured interviews were conducted and the interviews were transcribed and coded to identify emergent and recurrent themes.

RESULTS

Thirty interviews were conducted and the majority of the interviewees considered the EQ-5D-5 L insufficiently comprehensive to illustrate their HRQoL. While some key HRQoL aspects included in the EQ-5D matched with the community's HRQoL perception, respondents showed concern about the potential overlap of the existing HRQoL dimension, the optimal number or attributes, and the appropriateness of the EQ-VAS. Among the potential bolt-on dimensions that emerged, 'Sleep', 'Interpersonal Relationship', and 'Satisfaction' were the key potential bolt-on dimensions identified and emphasized in the interviews.

CONCLUSIONS

The qualitative findings of the study illustrate the possible gap between EQ-5D-5 L measurements and community HRQoL perception, while the findings support the development of EQ-5D bolt-on dimensions in the target community with content and face validity.

Developing and testing culturally relevant bolt-on items for EQ-5D-5L in Chinese populations: a mixed-methods study protocol

INTRODUCTION

EQ-5D is one of the most frequently used health-related quality of life (HRQoL) measures but has been found to be insensitive in detecting differences in health status in some general populations and disease groups. For example, the appropriateness of applying EQ-5D in the Chinese cultural setting has been widely discussed. Adding additional HRQoL dimensions (bolt-on items) can be a solution to both retain the original descriptive system of EQ-5D, while enhancing its sensitivity to the local context. To date, no studies have proposed culturally relevant bolt-ons for China or examined the psychometric properties of such bolt-on items. This protocol documents the identification, development, selection and psychometric testing of culturally relevant bolt-on items for EQ-5D-5L in China.

METHODS AND ANALYSIS

We will identify and develop candidate bolt-on items that are most relevant in the Chinese culture, through former literature reviews on health concepts important for the Chinese population, conducting expert consultations and qualitative interviews. We will quantitatively test the acceptability and measurement properties (including distributional characteristics and construct validity) of the candidate items in both general and disease populations in a cross-sectional setting. The patient group will be followed up to collect two-time-point data to assess test-retest reliability of the candidate items. Bolt-on item selection will consider both the qualitative and quantitative evidence gathered. This protocol outlines a comprehensive mixed-methods process for identifying, developing, selecting and testing bolt-on items that are relevant and culturally appropriate in China. This study may serve as a guide for similar initiatives in other cultural contexts.

ETHICS AND DISSEMINATION

This study received ethics approval from the Institutional Review Board of School of Public Health, Fudan University (IRB number: 2022-TYSQ-03-154). Study findings will be disseminated through international peer-reviewed journal articles as well as public, academic presentations at national and international conferences.

Normative profile of the EQ-5D-5L dimensions, EQ-5D-5L index and EQ-VAS scores for the general Thai population

PURPOSE

To generate a normative profile for the EQ-5D-5L dimensions, EQ-5D-5L index, and EQ-VAS scores of the general Thai population and to examine the associations between sociodemographic characteristics and their norm-based scores.

METHODS

Data from 2019 general Thai samples were employed to estimate the norm-based scores elicited using the Thai EQ-5D-5L value set. Descriptive statistics were used to estimate the norm-based scores stratified by gender and six age bands to obtain the normative profile for the general Thai population. Multivariable logistic and Tobit regression models were used to investigate the relationships between sociodemographic characteristics and EQ-5D-5L dimensions, EQ-5D-5L index, and EQ-VAS scores.

RESULTS

The mean EQ-5D-5L index and EQ-VAS scores were 0.931 and 82.3, respectively. Approximately 88.9% of the participants reported 19 out of 3125 (3%) possible health states. The odds of having problems with mobility was greatest for the sample aged ≥ 65 years and declined with decreasing age. Women, samples with advancing age, and those with a household income of ≤ 10,000 Baht/month and fair and poor health perceptions were more likely to report a lower EQ-5D-5L index. Furthermore, advanced age and fair and poor health perception were significantly associated with lower EQ-VAS scores.

CONCLUSION

The EQ-5D-5L population norms were established as the benchmark for both EQ-5D-5L index and EQ-VAS scores for the general Thai population. This is expected to support the health service research and inform policymakers on the allocation of limited healthcare resources.

The remarkably frequent use of EQ-5D in non-economic research

INTRODUCTION

EQ-5D is an instrument which has been utilized for a variety of purposes, including in health-economic appraisals as an input into quality-adjusted life year (QALY) calculations. Indeed, it is the most-widely applied instrument for health-economic appraisal worldwide, and is recommended for use in QALY calculations by many national Health Technology Assessment (HTA) agencies. There is also a growing body of evidence for its usefulness in a variety of settings other than economic appraisals, but such use has not been well-documented. This study addresses this issue and documents how EQ-5D has been applied in both the non-economic and economic contexts.

METHODS

The PubMed database was searched using the terms 'EQ-5D', 'EQ-5D AND cost', and 'EQ-5D AND cost AND QALY' from 1 January 1980 to 31 December 2019. We concentrated on 2019 publications for more detailed analyses. All the data collected for 2019 were downloaded and collected in EndNote. For 2019 only, we classified economic and non-economic use based on the inclusion of 'cost'. We also checked by manual inspection whether the search terms were suitable in correctly identifying economic and non-economic use. Variants of the non-economic use of EQ-5D were classified as follows: (a) as a quality of life outcome measure; (b) as a tool for methodological research; (c) methodological issues of EQ-5D itself; (d) comparisons with other quality of life questionnaires; (e) mapping studies; (f) value sets; (g) alongside costs but no QALY calculated; and (h) other.

RESULTS

The first publication found was from 1990. Up to and including 2019, 10,817 publications were identified, of which more than two in three did not contain any reference to costs or QALYs. In 2019, a total of 1409 manuscripts were identified, of which 239 were specifically for EQ-5D-5L.  Four hundred and seven (28.9%) included some form of 'costs' and 157 (11.1%) both 'costs' AND 'QALYs' terms. For EQ-5D-5L, the corresponding numbers were 104 (43.5%) and 29 (12.1%), respectively. After manually checking all the 1409 papers, three were duplicated records, which were omitted. In the remaining 1406 papers, only 40 (2.8%) contained the term 'cost', but not 'cost per QALY', and only 117 (8.3%) were identifiable as economic evaluations using the term 'cost per QALY'. Most non-economic use of EQ-5D was as a quality-of-life outcome measure (72.8%). Other applications were: as a tool for methodological research (6.7%); comparison studies (3.7%); EQ-5D methodological issues (3.5%); containing costs but not QALYs (2.8%); mapping (1.3%); value sets (0.4%); and other papers (0.4%).

CONCLUSIONS

The majority of the studies retrieved, covering a wide variety of research areas, reported upon the non-economic use of EQ-5D. Despite being the most-used instrument worldwide for QALY calculations, economic appraisal accounted for only a small, but important, part of published use.

Perceptions of the General Public About Health-related Quality of Life and the EQ-5D Questionnaire: A Qualitative Study in Korea

OBJECTIVES

The aim of this qualitative study was to investigate how members of the general public in Korea interpret the concept of health, and which dimensions of health are most important to them. We also explored their perceptions of the EuroQoL 5-Dimension (EQ-5D), including the EuroQoL visual analogue scale (EQ-VAS).

METHODS

We conducted face-to-face, in-depth interviews with 20 individuals from the general population, using a semi-structured interview guide. Content analysis was performed with verbatim transcripts and field notes to identify codes and categorize them according to their similarities and associations.

RESULTS

In total, 734 different codes were derived and classified into 4 categories. Participants cited the importance of both the mental and physical aspects of health, although they emphasized that the physical aspects appeared to play a larger role in their conceptualization of health. Participants noted that the EQ-5D has the advantage of being composed of 5 dimensions that are simple and contain both physical and mental areas necessary to describe health. However, some of them mentioned the need to add more dimensions of mental health and social health. Participants showed great satisfaction with the visually well-presented EQ-VAS. However, participants opined that the EQ-VAS scores might not be comparable across respondents because of different ways of responding to the scale.

CONCLUSIONS

While physical health is a fundamental aspect of health, mental and social aspects are also important to Koreans. The content of the EQ-5D broadly matched the attributes of health considered important by Koreans.

Investigating the Added Value of the EQ-5D-5L With Two Bolt-On Items in Patients With Hemophilia

Objective: This study examined the impact of adding two condition-specific bolt-on items to the EQ-5D-5L and assessed their psychometric properties in patients with hemophilia.

Methods: The data were obtained from a nationwide cross-sectional online survey of patients with hemophilia in China. Self-reported and proxy-reported data were analyzed separately. Ceiling effect, informativity, and discriminatory power of the EQ-5D-5L with two bolt-on items, dignity (DG), and bleeding (BL), were examined. Spearman's rank correlation (rho) was used to assess the associations of the EQ-5D-5L and two bolt-on items with the Hemophilia Quality of Life Questionnaire for Adults (Haem-A-QoL) and SF-12. Multiple regression analysis was performed to evaluate the explained variance of the EQ-5D-5L and bolt-on items in predicting EQ-VAS scores.

Results: A total of 895 patients and 222 caregivers completed the questionnaire. The ceiling effect decreased from 1.9 to 0.6% and 5.9 to 0.9% when using the EQ-5D-5L and the EQ-5D-5L with two bolt-on items among participants with both self- and proxy-completed questionnaires. Both DG and BL were strongly correlated with Haem-A-QoL sum score [rho: DG = 0.64 (patient) vs. 0.66(proxy); BL = 0.49 (patient) vs. 0.31 (proxy)], SF-12 mental component [rho: DG = −0.36 (patient) vs. −0.41 (proxy); BL = −0.53 (patient) vs. −0.57(proxy)], and SF-12 physical component [rho: DG = −0.61 (patient) vs. −0.61 (proxy); BL = −0.35 (patient) vs. −0.39 (proxy)]. Known-group comparisons confirmed that the two bolt-on items had satisfactory discriminatory power. Multiple regression analysis indicated that adding two bolt-on items significantly increased the ability to predict EQ-VAS scores. The adjusted R² increased by 8.2 and 8.8% for reports completed by the patients or patients' proxy respondents, respectively.

Conclusion: Adding the DG and BL bolt-on items can increase performance on the EQ-5D-5L in patients with hemophilia. A future valuation study will be carried out.

The Functional Assessment of Cancer Therapy Eight Dimension (FACT-8D), a Multi-Attribute Utility Instrument Derived From the Cancer-Specific FACT-General (FACT-G) Quality of Life Questionnaire: Development and Australian Value Set

OBJECTIVES

To develop a cancer-specific multi-attribute utility instrument derived from the Functional Assessment of Cancer Therapy - General (FACT-G) health-related quality of life (HRQL) questionnaire.

METHODS

We derived a descriptive system based on a subset of the 27-item FACT-G. Item selection was informed by psychometric analyses of existing FACT-G data (n = 6912) and by patient input (n = 82). We then conducted an online valuation survey, with participants recruited via an Australian general population online panel. A discrete choice experiment (DCE) was used, with attributes being the HRQL dimensions of the descriptive system and survival duration, and 16 choice-pairs per participant. Utility decrements were estimated with conditional logit and mixed logit modeling.

RESULTS

Eight HRQL dimensions were included in the descriptive system: pain, fatigue, nausea, sleep, work, social support, sadness, and future health worry; each with 5 levels. Of 1737 panel members who accessed the valuation survey, 1644 (95%) completed 1 or more DCE choice-pairs and were included in analyses. Utility decrements were generally monotonic; within each dimension, poorer HRQL levels generally had larger utility decrements. The largest utility decrements were for the highest levels of pain (-0.40) and nausea (-0.28). The worst health state had a utility of -0.54, considerably worse than dead.

CONCLUSIONS

A descriptive system and preference-based scoring approach were developed for the FACT-8D, a new cancer-specific multi-attribute utility instrument derived from the FACT-G. The Australian value set is the first of a series of country-specific value sets planned that can facilitate cost-utility analyses based on items from the FACT-G and related FACIT questionnaires containing FACT-G items.

Methods Used to Identify, Test, and Assess Impact on Preferences of Bolt-Ons: A Systematic Review

OBJECTIVES

The question of whether additional dimensions should be added to the EQ-5D, so-called bolt-ons, has been researched since the 1990s. Several candidate bolt-ons have been tested. The aim of this systematic review was to provide an overview of EQ-5D bolt-on studies, including the origin of possible suitable bolt-ons, their format, and methods that were used to examine their value.

METHODS

Studies were identified through database search and reference screening and assessed based on a set of inclusion criteria. All studies that investigated bolt-ons for the EQ-5D were eligible for inclusion. Two reviewers independently extracted information from all included studies on objectives, study design, EQ-5D version used, the investigated bolt-ons, methods used to achieve objectives, and outcomes.

RESULTS

Of 308 initially identified studies, 28 studies met the inclusion criteria. Of these studies, 3 identified potentially suitable bolt-on dimensions, 13 investigated the psychometric performance of EQ-5D + bolt-on(s), and 6 investigated the impact of the bolt-on on health state preferences. In total, 26 bolt-ons were identified, of which cognition was the most frequently mentioned. A wide variety of bolt-on identification methods, psychometric performance tests, and health state valuation methods were used in the included studies.

CONCLUSION

A range of bolt-on dimensions has been investigated using diverse methods. Guidelines are needed to standardize the wording of the bolt-on dimension and response options, evaluate minimal important gain of the bolt-on, and facilitate quality assessment of bolt-on studies. Subsequently, guidelines will facilitate decision making on whether or not to implement a bolt-on dimension to the EQ-5D.

Factors contributing to the ceiling effect of the EQ-5D-5L: an analysis of patients with prostate cancer judged "no-problems"

Purpose

The goal of the present study was to determine factors related to a ceiling effect (CE) on the EQ-5D-5L among Japanese patients with prostate cancer (PC).

Methods

An existent cross-sectional observational study dataset was used. Patients were ≥ 20 years of age and diagnosed with PC. For CE determinants on the EQ-5D-5L, we excluded possible “full-health” patients flagged by the EQ-VAS (score = 100) and/or FACT-P (score = 156) instruments. We then divided them into binary variables: A CE group (EQ-5D-5L score = 1) and others (< 1). The associations between CE, sociodemographic and medical characteristics, and FACT-P subscale scores were examined using a multivariate LASSO selection followed by a binomial logistic regression analysis performed to calculate odds ratios (ORs) and 95% confidence intervals (CIs).

Results

A total of 362 patients were analyzed. The LASSO selection variables, including all obtained variables, were as follows: age, palliative treatment, FACT-P physical well-being, and PC subscale score. Statistically significant variables predicting CE were palliative treatment (OR 0.23; 95% CI 0.09–0.60), physical well-being (OR 1.54; 95% CI 1.34–1.76), and PC subscale (OR 1.08; 95% CI 1.03–1.14).

Conclusions

This study revealed that palliative treatment and two FACT-P physical well-being and PC subscale scores were positively related to CE on the EQ-5D-5L. To our knowledge, this is the first study to examine predictors of CE on the EQ-5D-5L. The present results may be helpful for facilitating the consideration of “bolt-on” studies from the standpoint of PC patients.

A systematic review of the development and testing of additional dimensions for the EQ-5D descriptive system

Introduction: As the five dimensions of the EQ-5D might be insensitive to some populations or conditions, adding one or more specific 'bolt-on dimensions', to the EQ-5D may improve its validity and relevance for those groups. Various bolt-on dimensions have been identified and tested the effect on the psychometric performance and utility measurement. Therefore, this systematic review was to review all bolt-on dimensions and report the results of those two effects. Areas covered: Twelve studies were identified through PubMed, Scopus, and Web of Sciences from inception to January 2019. The bolt-on dimensions generally improved the EQ-5D's psychometric performance when compared with the standard version. However, evidence is lacking about the impact of bolt-on dimensions on responsiveness, reliability and known-groups validity. Evidence was also mixed for adding a sleep dimension, while interpersonal relationships did not promote a significant improvement on utility measurement. Expert opinion: Adding bolt-on dimensions could enhance the discriminative power and utility measurement of the EQ-5D; however, careful investigation of the sleep and interpersonal relationships is required since the evidence did not support a significant improvement. Further investigation of the identified bolt-on dimensions on all of the psychometric performance and the incremental utility scores derived from TTO is greatly encouraged.