Development of a new health-related quality of life measure for people with diabetes who experience hypoglycaemia: the Hypo-RESOLVE QoL

AIMS/HYPOTHESIS

Valid and reliable patient-reported outcome measures are vital for assessing disease impact, responsiveness to healthcare and the cost-effectiveness of interventions. A recent review has questioned the ability of existing measures to assess hypoglycaemia-related impacts on health-related quality of life for people with diabetes. This mixed-methods project was designed to produce a novel health-related quality of life patient-reported outcome measure in hypoglycaemia: the Hypo-RESOLVE QoL.

METHODS

Three studies were conducted with people with diabetes who experience hypoglycaemia. In Stage 1, a comprehensive health-related quality of life framework for hypoglycaemia was elicited from semi-structured interviews (N=31). In Stage 2, the content validity and acceptability of draft measure content were tested via three waves of cognitive debriefing interviews (N=70 people with diabetes; N=14 clinicians). In Stage 3, revised measure content was administered alongside existing generic and diabetes-related measures in a large cross-sectional observational survey to assess psychometric performance (N=1246). The final measure was developed using multiple evidence sources, incorporating stakeholder engagement.

RESULTS

A novel conceptual model of hypoglycaemia-related health-related quality of life was generated, featuring 19 themes, organised by physical, social and psychological aspects. From a draft version of 76 items, a final 14-item measure was produced with satisfactory structural (χ2=472.27, df=74, p<0.001; comparative fit index =0.943; root mean square error of approximation =0.069) and convergent validity with related constructs (r=0.46-0.59), internal consistency (α=0.91) and test-retest reliability (intraclass correlation coefficient =0.87).

CONCLUSIONS/INTERPRETATION

The Hypo-RESOLVE QoL is a rigorously developed patient-reported outcome measure assessing the health-related quality of life impacts of hypoglycaemia. The Hypo-RESOLVE QoL has demonstrable validity and reliability and has value for use in clinical decision-making and as a clinical trial endpoint.

DATA AVAILABILITY

All data generated or analysed during this study are included in the published article and its online supplementary files ( https://doi.org/10.15131/shef.

DATA

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Mapping from SIBDQ to EQ-5D-5L for patients with inflammatory bowel disease

OBJECTIVE

Clinical studies commonly use disease-specific measures to assess patients' health-related quality of life. However, economic evaluation often requires preference-based utility index scores to calculate cost per quality-adjusted life-year (QALY). When utility index scores are not directly available, mappings are useful. To our knowledge, no mapping exists for the Short Inflammatory Bowel Disease Questionnaire (SIBDQ). Our aim was to develop a mapping from SIBDQ to the EQ-5D-5L index score with German weights for inflammatory bowel disease (IBD) patients.

METHODS

We used 3856 observations of 1055 IBD patients who participated in a randomised controlled trial in Germany on the effect of introducing regular appointments with an IBD nurse specialist in addition to standard care with biologics. We considered five data availability scenarios. For each scenario, we estimated different regression and machine learning models: linear mixed-effects regression, mixed-effects Tobit regression, an adjusted limited dependent variable mixture model and a mixed-effects regression forest. We selected the final models with tenfold cross-validation based on a model subset and validated these with observations in a validation subset.

RESULTS

For the first four data availability scenarios, we selected mixed-effects Tobit regressions as final models. For the fifth scenario, mixed-effects regression forest performed best. Our findings suggest that the demographic variables age and gender do not improve the mapping, while including SIBDQ subscales, IBD disease type, BMI and smoking status leads to better predictions.

CONCLUSION

We developed an algorithm mapping SIBDQ values to EQ-5D-5L index scores for different sets of covariates in IBD patients. It is implemented in the following web application: https://www.bwl.uni-hamburg.de/hcm/forschung/mapping.html .

Comparison of four value sets derived using different TTO and DCE approaches: application to the new region-specific PBM, AP-7D

BACKGROUND

AP-7D is a newly developed preference-based measure (PBM) in East and Southeast Asia. However, no value set has been established yet. Comparison of the characteristics of value sets obtained by different methods is necessary to consider the most appropriate methodology for valuation survey of AP-7D.

METHOD

We surveyed the general population's preference of AP-7D health states by four valuation methods (a) composite time trade-off (cTTO); (b) simple discrete choice experiment (DCE); (c) DCE with duration; and (d) ternary DCE. In Japan, we collected approximately 1,000 samples for cTTO tasks through a face-to-face survey and 2,500 samples for each of the three DCE tasks. Respondents were selected through quota sampling based on the sex and age. The cTTO data were analyzed using a linear mixed and tobit model; the DCE data were analyzed using a simple and panel conditional logit model. Where the results of the analysis showed inconsistencies, a constrained model was used.

RESULTS

Since all the unconstrained models, except simple DCE, showed one or more inconsistencies, the constrained model was used for the analyses. The minimum values for the models were as follows: TTO model, -0.101; simple DCE model, -0.106; DCE with duration model, -0.706; ternary DCE model, -0.306. The score for the DCE with the duration model was much lower than that for the other models. Although the value sets for AP-7D differed among the four valuation methods, the ternary DCE model showed intermediate characteristics between those of the cTTO and DCE with duration models. As compared with to EQ-5D-5L, the distributions of all the scores on the Japanese AP-7D moved to the left. Although "Energy" was one of the domains with the least influence on the AP-7D score in all four models, "Burden to others" had the largest impact on the preferences.

CONCLUSION

We constructed four value sets using different TTO and DCE methods. Our findings are expected not only to contribute to the development of AP-7D, but also other preference-based measures.

A Spanish value set for the SF-6D based on the SF-12 v1

AIM

This paper reports the first estimation of an SF-6D value set based on the SF-12 for Spain.

METHODS

A representative sample (n = 1020) of the Spanish general population valued a selection of 56 hypothetical SF-6D health states by means of a probability lottery equivalent (PLE) method. The value set was derived using both random effects and mean models estimated by ordinary least squares (OLS). The best model was chosen on the basis of its predictive ability assessed in terms of mean absolute error (MAE).

RESULTS

The model yielding the lowest MAE (0.075) was that based on main effects using OLS. Pain was the most significant dimension in predicting health state severity. Comparison with the previous SF-6D (SF-36) model estimated for Spain revealed no significant differences, with a similar MAE (0.081). Nevertheless, the new SF-6D (SF-12) model predicted higher utilities than those generated by the SF-6D (SF-36) scoring algorithm (minimum value - 0.071 vs - 0.357).

CONCLUSION

A value set for the SF-6D (SF-12) based on Spanish general population preferences elicited by means of a PLE technique is successfully estimated. The new estimated SF-6D (SF-12) preference-based measure provides a valuable tool for researchers and policymakers to assess the cost-effectiveness of new health technologies in Spain.

Mapping Short Warwick and Edinburgh Mental Wellbeing Scale (SWEMWBS) to Recovering Quality of Life (ReQoL) to estimate health utilities

BACKGROUND

The Short Warwick and Edinburgh Mental Wellbeing Scale (SWEMWBS) is a widely used non-preference-based measure of mental health in the UK. The primary aim of this paper is to construct an algorithm to translate the SWEMWBS scores to utilities using the Recovering Quality of Life Utility Index (ReQoL-UI) measure.

METHODS

Service users experiencing mental health difficulties were recruited in two separate cross-sectional studies in the UK. The following direct mapping functions were used: Ordinary Least Square, Tobit, Generalised Linear Models. Indirect (response) mapping was performed using seemingly unrelated ordered probit to predict responses to each of the ReQoL-UI items and subsequently to predict using UK tariffs of the ReQoL-UI from SWEMWBS. The performance of all models was assessed by the mean absolute errors, root mean square errors between the predicted and observed utilities and graphical representations across the SWEMWBS score range.

RESULTS

Analyses were based on 2573 respondents who had complete data on the ReQoL-UI items, SWEMWBS items, age and sex. The direct mapping methods predicted ReQoL-UI scores across the range of SWEMWBS scores reasonably well. Very little differences were found among the three regression specifications in terms of model fit and visual inspection when comparing modelled and actual utility values across the score range of the SWEMWBS. However, when running simulations to consider uncertainty, it is clear that response mapping is superior.

CONCLUSIONS

This study presents mapping algorithms from SWEMWBS to ReQoL as an alternative way to generate utilities from SWEMWBS. The algorithm from the indirect mapping is recommended to predict utilities from the SWEMWBS.

Obtaining preference scores for an abbreviated self-completion version of the Teen-Addiction Severity Index (ASC T-ASI) to value therapy outcomes of systemic family interventions: a discrete choice experiment

BACKGROUND

Systemic family interventions for adolescents with problems of substance use and/or delinquency are increasingly focused subject of economic evaluations. Treatment effects go beyond improvements in commonly measured health-related quality of life (HRQOL). The Teen-Addiction Severity Index (T-ASI) was identified as capable of capturing these broad outcomes. However, it lacks preference-based scores. An abbreviated self-completion version (ASC T-ASI) was created and validated, covering the T-ASI domains substance use, school, work, family, social relationships, justice, and mental health. This study aimed to obtain societal preference scores for the ASC T-ASI.

METHODS

Preferences were elicited in a sample of the Dutch general adult population (n = 1500), using a web-based Discrete Choice Experiment. Choice tasks included two unlabeled alternatives with attributes and levels corresponding to the domains and levels of the ASC T-ASI. A pilot study (n = 106) informed priors, optimal presentation, and number of choice tasks applied in the main study. Data were analyzed using a mixed multinomial logit model.

RESULTS

Preference scores were logically ordered, with lower scores for worse ASC T-ASI states. Scores were most influenced by reductions in problems concerning the domains substance use, mental health, justice, and family. Tariffs were calculated for each ASC T-ASI state, ranging from 0 (worst situation) to 1 (best situation).

CONCLUSIONS

The tariffs enable preference-based assessments of the broad effects of systemic family interventions for adolescents with problems of substance use and/or delinquency. The outcome reflects addiction-related rather than health-related utility and can be used next to generic HRQOL instruments in relevant economic evaluations. Given the source used for the preferences, interpretations and valuation of scores require attention.

China Health Related Outcomes Measures (CHROME): development of a descriptive system to support cardiovascular disease specific preference-based measure for the Chinese population

PURPOSE

Preference-based measures have been increasingly recommended to measure health outcomes for economic evaluation. However, none of existing cardiovascular disease (CVD)-specific health-related quality of life (HRQoL) instruments are preference-based. This study aimed to develop the descriptive system of preference-based HRQoL instrument for Chinese patients with CVDs under the Initiative of China Health Related Outcomes Measures (CHROME).

METHODS

Qualitative face-to-face interviews were conducted with Chinese patients with CVDs. Content analysis was employed to generate candidate items for the instrument. Then expert consultation and cognitive debriefing interviews were conducted to guide further selection and revision of the items.

RESULTS

We interviewed 127 CVD patients with 67.7% being male and 63.8% living in the urban area. A hierarchical code book comprised of four themes, 20 categories, 62 sub-categories, and 207 codes, was developed. Candidate items were selected based on the criteria set by the Consensus-based Standards for the selection of health Measurement Instruments (COSMIN) methodology and ISPOR PRO guidance. An online survey and meeting with an expert advisory panel (n = 15) followed by cognitive debriefing interviews with 20 patients and 13 physicians were conducted to further select and revise the candidate items. The descriptive system of CHROME-CVD consists of 14 items, namely frequency and severity of chest pain, chest tightness, palpitation, shortness of breath, dizziness, fatigue, appetite, sleeping, mobility, daily activities, depression, worry, and social relationship. Four or five level responses were selected based on cognitive debriefing results to each item.

CONCLUSION

The current study developed the descriptive system (items and response options) of CHROME-CVD, the future CVD-specific preference-based HRQoL instrument for Chinese CVD patients.

Assessing feasibility, construct validity, and reliability of a new aged care-specific preference-based quality of life instrument: evidence from older Australians in residential aged care

BACKGROUND

Quality of Life-Aged Care Consumers (QOL-ACC) is a new older-person-specific quality of life instrument designed for application in quality assessment and economic evaluation in aged care. The QOL-ACC was designed from its inception with older people receiving aged care services ensuring its strong content validity. Given that the QOL-ACC has already been validated in home care settings and a preference-weighted value set developed, we aimed to assess feasibility, construct validity and reliability of the QOL-ACC in residential aged care settings.  METHODS: Individuals living in residential aged care facilities participated in an interviewer-facilitated survey. The survey included the QOL-ACC, QCE-ACC (quality of aged care experience measure) and two other preference-based quality of life instruments (ASCOT and EQ-5D-5L). Feasibility was assessed using missing data and ceiling/floor effects. Construct validity was assessed by exploring the relationship between the QOL-ACC and other instruments (convergent validity) and the QOL-ACC's ability to discriminate varying levels of self-rated health and quality of life. Internal consistency reliability was assessed using Cronbach's alpha (α).

RESULTS

Of the 200 residents (mean age, 85 ± 7.7 years) who completed the survey, 60% were female and 69% were born in Australia. One in three participating residents self-rated their health as fair/poor. The QOL-ACC had no missing data but had small floor effects (0.5%) and acceptable ceiling effects (7.5%). It demonstrated moderate correlation with ASCOT (r = 0.51, p < 0.001) and EQ-5D-5L (r = 0.52, p < 0.001) and a stronger correlation with the QCE-ACC (r = 0.57, p < 0.001). Residents with poor self-rated health and quality of life had significantly lower scores on the QOL-ACC. The internal consistency reliability of the QOL-ACC and its dimensions was good (α = 0.70-0.77).

CONCLUSIONS

The QOL-ACC demonstrated good feasibility, construct validity and internal consistency reliability to assess aged care-related quality of life. Moderate correlations of the QOL-ACC and other instruments provide evidence of its construct validity and signifies that the QOL-ACC adds non-redundant and non-interchangeable information beyond the existing instruments. A stronger correlation with the QCE-ACC than other instruments may indicate that quality of life is more intimately connected with the care experience than either health- or social-related quality of life in residential aged care settings.

Assessing the construct validity of the Quality-of-Life-Aged Care Consumers (QOL-ACC): an aged care-specific quality-of-life measure

PURPOSE

To evaluate the construct (convergent and known group) validity of the Quality-of-Life-Aged Care Consumer (QOL-ACC), an older-person-specific quality-of-life measure designed for application in quality assessment and economic evaluation in aged care.

METHODS

Convergent validity was assessed by examining relationships with other validated preference-based measures (EQ-5D-5L, ASCOT), quality of aged care experience (QCE-ACC) and life satisfaction (PWI) through an online survey. Known-group validity was assessed by testing the ability to discriminate varying levels of care needs, self-reported health and quality of life.

RESULTS

Older people (aged ≥ 65 years) receiving community-aged care (N = 313) responded; 54.6% were female, 41.8% were living alone and 56.8% were receiving higher-level care. The QOL-ACC and its six dimensions were low to moderately and significantly correlated with the EQ-5D-5L (correlation co-efficient range, ρ = 0.39-0.56). The QOL-ACC demonstrated moderate and statistically significant correlations with ASCOT (ρ = 0.61), the QCE-ACC (ρ = 0.51) and the PWI (ρ = 0.70). Respondents with poorer self-reported health status, quality of life and/or higher-level care needs demonstrated lower QOL-ACC scores (P < 0.001), providing evidence of known-group validity.

CONCLUSIONS

The study provides evidence of the construct validity of the QOL-ACC descriptive system. A preference-weighted value set is currently being developed for the QOL-ACC, which when finalised will be subjected to further validation assessments.

Development of the SF-6Dv2 health utility survey: comprehensibility and patient preference

Background

The SF-6Dv2 classification system assesses health states in six domains—physical functioning, role function, bodily pain, vitality, social functioning, and mental health. Scores have previously been derived from the SF-36v2® Health Survey. We aimed to develop a six-item stand-alone SF-6Dv2 Health Utility Survey (SF-6Dv2 HUS) and evaluate its comprehensibility.

Methods

Two forms of a stand-alone SF-6Dv2 HUS were developed for evaluation. Form A had 6 questions with 5–6 response choices, while Form B used 6 headings and 5–6 statements describing the health levels within each domain. The two forms were evaluated by 40 participants, recruited from the general population. Participants were randomized to debrief one form of the stand-alone SF-6Dv2 HUS during a 75-min interview, using think-aloud techniques followed by an interviewer-led detailed review. Participants then reviewed the other form of SF-6Dv2 and determined which they preferred. Any issues or confusion with items was recorded, as was as overall preference. Data were analyzed using Microsoft Excel and NVivo Software (v12).

Results

Participants were able to easily complete both forms. Participant feedback supported the comprehensibility of the SF-6Dv2 HUS. When comparing forms, 25/40 participants preferred Form A, finding it clearer and easier to answer when presented in question/response format. The numbered questions and underlining of key words in Form A fostered quick and easy comprehension and completion of the survey. However, despite an overall preference for Form A, almost half of participants (n = 19) preferred the physical functioning item in Form B, with more descriptive response choices.

Conclusion

The results support using Form A, with modifications to the physical functioning item, as the stand-alone SF-6Dv2 HUS. The stand-alone SF-6Dv2 HUS is brief, easy to administer, and comprehensible to the general population.

Adapting preference-based utility measures to capture the impact of cancer treatment-related symptoms

It is important that patient-reported outcome (PRO) measures used to assess cancer therapies adequately capture the benefits and risks experienced by patients, particularly when adverse event profiles differ across therapies. This study explores the case for augmenting preference-based utility measures to capture the impact of cancer treatment-related symptoms. Additional cancer treatment-related items could be specific (e.g., rash) or global. While specific items are easier to describe and understand, their use may miss rarer symptoms and those that are currently unknown but will arise from future medical advancements. The appropriate number of additional items, the independence of those items, and their impact on the psychometric properties of the core instrument require consideration. Alternatively, a global item could encompass all potential treatment-related symptoms, of any treatments for any disease. However, such an item may not be well understood by general public respondents in valuation exercises. Further challenges include the decision about whether to generate de novo value sets for the modified instrument or to map to existing tariffs. The fluctuating and transient nature of treatment-related symptoms may be inconsistent with the methods used in conventional valuation exercises. Fluctuating symptoms could be missed by sub-optimal measure administration timing. The addition of items also poses double-counting risks. In summary, the addition of treatment-related symptom items could increase the sensitivity of existing utility measures to capture known and unknown treatment effects in oncology, while retaining the core domains. However, more research is needed to investigate the challenges, particularly regarding valuation.

An international mixed methods study to develop a new preference-based measure for women with breast cancer: the BREAST-Q Utility module

BACKGROUND

Generic preference-based measures (PBM), though commonly used, may not be optimal for use in economic evaluations of breast cancer interventions. No breast cancer-specific PBM currently exists, and the generic PBMs fail to capture the unique concerns of women with breast cancer (e.g., body image, appearance, treatment-specific adverse effects). Hence, the objective of this study was to develop a breast cancer-specific PBM, the BREAST-Q Utility module.

METHODS

Women diagnosed with breast cancer (stage 0-4, any treatment) were recruited from two tertiary hospitals in Canada and one in the US. The study followed an exploratory sequential mixed methods approach, whereby semi-structured interviews were conducted and at the end of the interview, participants were asked to list their top five health-related quality of life (HRQOL) concerns and to rate the importance of each item on the BREAST-Q. Interviews were audio-recorded, transcribed verbatim, and coded. Constant comparison was used to refine the codes and develop a conceptual framework. Qualitative and quantitative data were triangulated to develop the content of the Utility module  that was refined through 2 rounds of cognitive debriefing interviews with women diagnosed with breast cancer and feedback from experts.

RESULTS

Interviews were conducted with 57 women aged 55 ± 10 years. A conceptual framework was developed from 3948 unique codes specific to breasts, arms, abdomen, and cancer experience. Five top-level domains were HRQOL (i.e., physical, psychological, social, and sexual well-being) and appearance. Data from the interviews, top 5 HRQOL concerns, and BREAST-Q item ratings were used to inform dimensions for inclusion in the Utility module. Feedback from women with breast cancer (N = 9) and a multidisciplinary group of experts (N = 27) was used to refine the module. The field-test version of the HSCS consists of 10 unique dimensions. Each dimension is measured with 1 or 2 candidate items that have 4-5 response levels each.

CONCLUSION

The field-test version of the BREAST-Q Utility module was derived from extensive patient and expert input. This comprehensive approach ensured that the content of the Utility module is relevant, comprehensive, and includes concerns that matter the most to women with breast cancer.

Mapping EORTC QLQ-C30 and FACT-G onto EQ-5D-5L index for patients with cancer

Background

To develop direct and indirect (response) mapping algorithms from the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC QLQ-C30) and the Functional Assessment of Cancer Therapy General (FACT-G) onto the EQ-5D-5L index.

Methods

We conducted the QOL-MAC study where EQ-5D-5L, EORTC QLQ-C30, and FACT-G were cross-sectionally evaluated in patients receiving drug treatment for solid tumors in Japan. We developed direct and indirect mapping algorithms using 7 regression methods. Direct mapping was based on the Japanese value set. We evaluated the predictive performances based on root mean squared error (RMSE), mean absolute error, and correlation between the observed and predicted EQ-5D-5L indexes.

Results

Based on data from 903 and 908 patients for EORTC QLQ-C30 and FACT-G, respectively, we recommend two-part beta regression for direct mapping and ordinal logistic regression for indirect mapping for both EORTC QLQ-C30 and FACT-G. Cross-validated RMSE were 0.101 in the two methods for EORTC QLQ-C30, whereas they were 0.121 in two-part beta regression and 0.120 in ordinal logistic regression for FACT-G. The mean EQ-5D-5L index and cumulative distribution function simulated from the recommended mapping algorithms generally matched with the observed ones except for very good health (both source measures) and poor health (only FACT-G).

Conclusions

The developed mapping algorithms can be used to generate the EQ-5D-5L index from EORTC QLQ-C30 or FACT-G in cost-effectiveness analyses, whose predictive performance would be similar to or better than those of previous algorithms.

Development of a multiplicative, multi-attribute utility function and eight single-attribute utility functions for the Health Utilities Index Mark 3 in Japan

Background

The Health Utilities Index Mark 3 (HUI3) is a generic multi-attribute, preference-based system for assessing health-related quality of life. It is widely used overseas as an outcome measure and for estimating quality-adjusted life years. We aimed to estimate a multi-attribute and eight single-attribute utility functions for the HUI3 system based on community preferences in Japan. We conducted two preference surveys in this study. The first survey was designed to estimate a model of utility function and collect preference scores, and the second survey was designed to evaluate predictive validity of the utility function and provide independent scores. Values obtained from the feeling thermometer and standard gamble scores obtained from using a chance board were included in the preference scale. We recruited 1043 respondents (age: 20–79 years) from five cities in Japan through the general population classified by sex and age groups. Respondents were further randomly divided into a modeling group (n = 774) and a direct group (n = 263).

Results

We acquired the estimation for eight single-attribute and a global multi-attribute utility function. The minimum expected multi-attribute utility score was − 0.002. The intraclass correlation coefficient between the directly measured utility score and the score generated by multi-attribute function in terms of 53 health conditions was 0.742.

Conclusions

The HUI3 scoring function developed in Japan has a strong theoretical and empirical basis. It will be useful in future to predict the directly measured score of health technology assessments in Japan.

Translation, cultural adaptation and psychometric validation of the SF-6D measure of health-related quality of life for use in Arabic-Speaking countries

BACKGROUND

The SF-6D is a generic, six-dimensional health-related quality of life (HRQoL) measure derived from a selection of items from the SF-36.

OBJECTIVES

To translate, culturally adapt and validate the SF-6D for use in Arabic-speaking countries.

METHODS

The International Quality of Life Assessment (IQOLA) methodology was followed. Two forward translations, one consensus and one backward translation were undertaken. Difficulties encountered were categorized as grammatical, idiomatic, semantic/conceptual, and cultural. The content validity of the final version was tested and Cronbach's alpha test of internal consistency was used for assessing reliability. Confirmatory factor analysis (CFA), was also used to assess construct validity and to test a pre-specified relationship of observed measures.

RESULTS

Minor changes were made to the forward translation to improve cultural appropriateness. The Backward translation did not reveal major problems and equivalence to the original was confirmed following committee review. A total of 470 participants from Jordan, Egypt, UAE, Qatar and Palestine completed the translated SF-6D. All the incremental indices values are ≥0.90 and close to 1. Item loading values ranged from 0.52 to 0.87. The measurement model weight for those with chronic health conditions ranged from 0.68 to 0.91, and from 0.42 to 0.73 for those without. The percentage of variation in self-reported health state was about 55%. The measurement weight of SF-6D on self-reported health state among chronic responders was 0.87 while among responders reporting no chronic disease was 0.61. The t-value for the difference in measurement weight was -8.93 (p ≤ 0.01).

CONCLUSION

Arabic translation and cultural adaptation of SF-6D has resulted in an acceptable and culturally-adapted version that can be used in Arabic-speaking countries. Reliability and validity have been confirmed as well as ability to assess the difference in quality of life between patients with chronic health conditions and healthy individuals.

Developing a dementia-specific health state classification system for a new preference-based instrument AD-5D

Background

With an ageing population, the number of people with dementia is rising. The economic impact on the health care system is considerable and new treatment methods and approaches to dementia care must be cost effective. Economic evaluation requires valid patient reported outcome measures, and this study aims to develop a dementia-specific health state classification system based on the Quality of Life for Alzheimer’s disease (QOL-AD) instrument (nursing home version). This classification system will subsequently be valued to generate a preference-based measure for use in the economic evaluation of interventions for people with dementia.

Methods

We assessed the dimensionality of the QOL-AD to develop a new classification system. This was done using exploratory and confirmatory factor analysis and further assessment of the structure of the measure to ensure coverage of the key areas of quality of life. Secondly, we used Rasch analysis to test the psychometric performance of the items, and select item(s) to describe each dimension. This was done on 13 items of the QOL-AD (excluding two general health items) using a sample of 284 residents living in long-term care facilities in Australia who had a diagnosis of dementia.

Results

A five dimension classification system is proposed resulting from the three factor structure (defined as ‘interpersonal environment’, ‘physical health’ and ‘self-functioning’) derived from the factor analysis and two factors (‘memory’ and ‘mood’) from the accompanying review. For the first three dimensions, Rasch analysis selected three questions of the QOL-AD (‘living situation’, ‘physical health’, and ‘do fun things’) with memory and mood questions representing their own dimensions. The resulting classification system (AD-5D) includes many of the health-related quality of life dimensions considered important to people with dementia, including mood, global function and skill in daily living.

Conclusions

The development of the AD-5D classification system is an important step in the future application of the widely used QOL-AD in economic evaluations. Future valuation studies will enable this tool to be used to calculate quality adjusted life years to evaluate treatments and interventions for people diagnosed with mild to moderate dementia.