The Validity of Health-Related Quality of Life Instruments in Patients With Late-Stage Parkinson's Disease.

OBJECTIVE: To examine the validity of health-related quality of life (Hr-QoL) measures in patients with late-stage Parkinson's disease (PD). METHODS: We analysed data from patients with late-stage PD and their carers who were assessed with a range of clinical measures and the EQ-5D-3 L. The DEMQOL-Proxy was completed for 157 patients with a diagnosis of dementia and the PDQ-8 by 401 patients without dementia. Convergent validity was assessed using correlations with measures of Parkinson's severity, independence and cognitive function, and construct validity using correlations with patients' own EQ-5D-3 L scores. In addition, we assessed divergent validity using correlations with carers' own EQ-5D index, EQ-VAS and Zarit caregiver burden scores. RESULTS: In patients without dementia, both the PDQ-8 and EQ-5D-3 L correlated with measures of disease severity, dependence and carer burden scores, and PDQ-8 scores moderately with EQ-5D-3 L and EQ-5D-3 L VAS scores. In patients with dementia, EQ-5D-3 L scores correlated with disease severity, cognition and dependence scores, but DEMQOL-Proxy scores were moderately associated only with patients' dependence and carers' own EQ-5D-3 L scores but not patients' disease severity, EQ-5D-3 L or cognitive scores. CONCLUSIONS: The PDQ-8 and EQ-5D-3 L have adequate validity in late stage PD without dementia, but in those with PD and dementia the EQ-5D-3 L may be preferable to the DEMQOL-Proxy.

Estimating the minimum important difference in the DEMQOL instrument in people with dementia.

PURPOSE: The Dementia-Related Quality of Life (DEMQOL) measure and the DEMQOL-Utility Score (DEMQOL-U) are validated tools for measuring quality of life (QOL) in people with dementia. What score changes translate to a clinically significant impact on patients' lives was unknown. This study establishes the minimal important differences (MID) for these two instruments. METHODS: Anchor-based and distribution-based methods were used to estimate the MID scores from patients enrolled in a randomised controlled trial. For the anchor-based method, the global QOL (Q29) item from the DEMQOL was chosen as the anchor for DEMQOL and both Q29 and EQ-5D for DEMQOL-U. A one category difference in Q29, and a 0.07 point difference in EQ-5D score, were used to classify improvement and deterioration, and the MID scores were calculated for each category. These results were compared with scores obtained by the distribution-based methods. RESULTS: A total of 490 people with dementia had baseline DEMQOL data, of these 386 had 8-month data, and 344 had 12-month DEMQOL data. The absolute change in DEMQOL for a combined 1-point increase or decrease in the Q29 anchor was 5.2 at 8 months and 6.0 at 12 months. For the DEMQOL-U, the average absolute change at 8 and 12 months was 0.032 and 0.046 for the Q29 anchor and 0.020 and 0.024 for EQ-5D anchor. CONCLUSION: We present MID scores for the DEMQOL and DEMQOL-U instruments obtained from a large cohort of patients with dementia. An anchored-based estimate of the MID for the DEMQOL is around 5 to 6 points; and 0.02 to 0.05 points for the DEMQOL-U. The results of this study can guide clinicians and researchers in the interpretation of these instruments comparisons between groups or within groups of people with dementia. TRIAL REGISTRATION NUMBER AND DATE OF REGISTRATION: ISRCTN17993825 on 11th October 2016.

Proxy reporting of health-related quality of life for people with dementia: a psychometric solution.

BACKGROUND: The growing move towards personalised health and social care systems means that every effort needs to be made to generate patient-reported outcome data. However, the deteriorating nature of dementia can make it difficult for people with dementia to complete self-reported questionnaires and it is often necessary to rely on a family member (proxy) to report on their behalf. There is little evidence to guide how the difference between self- and proxy-reports of health reported quality of life (HRQL) in dementia can be interpreted. METHODS: We recruited people with dementia and their family carers from 78 memory Assessment Services in the UK. We used Rasch measurement methods to investigate whether a HRQL questionnaire known as DEMQOL (self-reported by the person with dementia) and DEMQOL-Proxy (proxy-reported by a family carer) can be placed on the same continuum and whether a revised scoring algorithm, based on this equated model, can be developed that takes account of the relationship between self- and proxy-reports. RESULTS: In a sample of 1434 patients and 1030 carers, our findings supported equating DEMQOL/DEMQOL-Proxy (overall fit to the model; no mis-fitting items) after addressing specific issues (eight disordered items requiring re-scoring, four pairs locally dependent items, and five items showing DIF). Cross walk tables have been produced. CONCLUSIONS: We have established for the first time that DEMQOL and DEMQOL-Proxy can be placed on the same continuum and that patients and carer proxies are reporting on the same construct when they complete these questionnaires. Where possible both DEMQOL and DEMQOL-Proxy should still be administered together, using the improved scoring algorithm reported here. Where only DEMQOL-Proxy is available, the cross walk tables provide an estimate of DEMQOL for a particular person from their DEMQOL-Proxy score.

How Should We Capture Health State Utility in Dementia? Comparisons of DEMQOL-Proxy-U and of Self- and Proxy-Completed EQ-5D-5L.

BACKGROUND: Dementia-specific and proxy-completed preference-based measures have been proposed for use in intervention studies involving people living in residential care, in instances where generic, self-reported preference-based measures have been deemed inappropriate. OBJECTIVE: This study was conducted to investigate the construct validity, criterion validity, and responsiveness of DEMQOL-Proxy-U and of self- and proxy-completed EQ-5D-5L. METHODS: The analysis used a 3-wave, individual-level data set of 1004 people living with dementia in residential care that included self-completed EQ-5D-5L and formal-carer and informal-carer proxy-completed EQ-5D-5L and DEMQOL-Proxy-U utility values, in addition to other nonutility cognitive measures (Functional Assessment Staging [FAST], Clinical Dementia Rating [CDR], Cohen-Mansfield Agitation Inventory [CMAI]) and health-related quality of life (HRQOL) measures (nursing home version of the Quality of Life with Alzheimer's disease scale [QOL-AD-NH], Quality of Life in Late-Stage Dementia [QUALID] scale). Construct validity, criterion validity, and responsiveness were assessed using correlation, Bland-Altman plots, and panel data regression models. RESULTS: Self-completed EQ-5D-5L failed to reflect clinically important differences and changes in FAST, CDR, and CMAI but did capture the resident's own view of HRQOL (QOL-AD-NH). As dementia severity increased, collection of EQ-5D-5L-proxy and DEMQOL-Proxy-U data was more feasible than collection of self-completed EQ-5D-5L. These formal-carer and informal-carer proxy measures also better reflected changes in FAST, CDR, and CMAI but did not capture the resident's own view of HRQOL (QOL-AD-NH), despite adequately capturing the proxy's own view of the resident's HRQOL (QUALID). This indicates discrepancies between a proxy's view and resident's view of the impact that tangible declines in health, cognition, or functional abilities have on HRQOL. The EQ-5D-5L-proxy and DEMQOL-Proxy-U were generally poor substitutes. Regardless of which proxy completed it, the EQ-5D-5L-proxy was typically more responsive than the DEMQOL-Proxy-U to changes in CDR, FAST, and CMAI, indicating that use of the DEMQOL-Proxy-U is not always justified. CONCLUSION: Disparities in the measurement properties of different utility measures mean that choices about how to measure utility in trials could affect economic evaluation outcomes and hence how resources are allocated for dementia care.

DEMQOL and DEMQOL-Proxy: a Rasch analysis among those diagnosed with dementia.

BACKGROUND: In previous work we concluded that DEMQOL and DEMQOL-Proxy can provide robust measurement of HRQL in dementia when scores are derived from analysis using the Rasch model. As the study sample included people with mild cognitive impairment, we undertook a replication study in the subsample with a diagnosis of dementia (PWD). PWD constitute the population for whom DEMQOL and DEMQOL-Proxy were originally developed. METHODS: We conducted a Rasch model analysis using the RUMM2030 software to re-evaluate DEMQOL (441 PWD) and DEMQOL-Proxy (342 family carers). We evaluated scale to sample targeting, ordering of item thresholds, item fit to the model, and differential item functioning (sex, age, severity, relationship), local independence, unidimensionality and reliability. RESULTS: For both DEMQOL and DEMQOL-Proxy, results were highly similar to the results in the original sample. We found the same problems with content and response options. CONCLUSIONS: DEMQOL and DEMQOL-Proxy can provide robust measurement of HRQL in people with a diagnosis of dementia when scores are derived from analysis using the Rasch model. As in the wider sample, the problems identified with content and response options require qualitative investigation in order to improve the scoring of DEMQOL and DEMQOL-Proxy.

An empirical comparison of the measurement properties of the EQ-5D-5L, DEMQOL-U and DEMQOL-Proxy-U for older people in residential care.

PURPOSE: This study aimed to empirically compare the measurement properties of self-reported and proxy-reported (in cases of severe cognitive impairment) generic (EQ-5D-5L) and condition-specific (DEMQOL-U and DEMQOL-Proxy-U) preference-based HRQoL instruments in residential care, where the population is characterised by older people with high rates of cognitive impairment, dementia and disability. METHODS: Participants were recruited from seventeen residential care facilities across four Australian states. One hundred and forty-three participants self-completed the EQ-5D-5L and the DEMQOL-U while three hundred and eight-seven proxy completed (due to the presence of severe dementia) the EQ-5D-5L and DEMQOL-Proxy-U. The convergent validity of the outcome measures and known group validity relative to a series of clinical outcome measures were assessed. RESULTS: Results satisfy convergent validity among the outcome measures. EQ-5D-5L and DEMQOL-U utilities were found to be significantly correlated with each other (p < 0.01) as were EQ-5D-5L and DEMQOL-Proxy-U utilities (p < 0.01). Both self-reported and proxy-reported EQ-5D-5L utilities demonstrated strong known group validity in relation to clinically recognised thresholds of cognition and physical functioning, while in contrast neither DEMQOL-U nor DEMQOL-Proxy-U demonstrated this association. CONCLUSIONS: The findings suggest that the EQ-5D-5L, DEMQOL-U and DEMQOL-Proxy-U capture distinct aspects of HRQoL for this population. The measurement and valuation of HRQoL form an essential component of economic evaluation in residential care. However, high levels of cognitive impairment may preclude self-completion for a majority. Further research is needed to determine cognition thresholds beyond which an individual is unable to reliably self-report their own health-related quality of life.

DEMQOL and DEMQOL-Proxy: a Rasch analysis.

BACKGROUND: DEMQOL and DEMQOL-Proxy are widely used patient reported outcome measures (PROMs) of health related quality of life in people with dementia (PWD). Growing interest in routine use of PROMs in health care calls for more robust instruments that are potentially fit for reliable and valid comparisons at the micro-level (patients) and meso-level (clinics, hospitals, care homes). METHODS: We used modern psychometric methods (based on the Rasch model) to re-evaluate DEMQOL (1428 PWDs) and DEMQOL-Proxy (1022 carers) to ensure they are fit for purpose. We evaluated scale to sample targeting, ordering of item thresholds, item fit to the model, and differential item functioning (sex, age, relationship), local independence, unidimensionality and reliability on the full set of items and a smaller item set. RESULTS: For both DEMQOL and DEMQOL-Proxy the smaller item set performed better than the original item set. We developed revised scores using the items from the smaller set. CONCLUSIONS: We have improved the scoring of DEMQOL and DEMQOL-Proxy using the Rasch measurement model. Future work should focus on the problems identified with content and response options.

Reliability and validity of a self-administration version of DEMQOL-Proxy.

OBJECTIVE: This study aimed to investigate the reliability and validity of a self-administered version of DEMQOL-Proxy, a disease-specific instrument that measures health-related quality of life in people with dementia. METHODS: The sample consisted of 173 informal carers of people with dementia, aged 29 to 89 years old. Carers were mostly female, White/White British and closely related to the patient. They completed DEMQOL-Proxy (self-administered), EQ-5D-3L (proxy reported about the person with dementia), EQ-5D-3L (self-reported about their own health) and the Zarit Burden Interview. Using well-established methods from classical test theory, we evaluated scale level acceptability, reliability and convergent, discriminant and known-groups validity of DEMQOL-Proxy. RESULTS: DEMQOL-Proxy (self-administered) showed high acceptability (3.5% missing data and 0% scores at floor or ceiling), high internal consistency reliability (α = 0.93) and good convergent and discriminant validity. Amongst others, we found a moderately high correlation with EQ-5D-3L proxy reported (r = 0.52) and low to essentially zero correlations with EQ-5D-3L self-reported (r = 0.20) and carer and patient background variables (r ≤ 0.20). As predicted, DEMQOL-Proxy (self-administered) showed a modest correlation with DEMQOL (r = 0.32). Known-groups differences on health-related quality of life (comparing people with versus people without cognitive impairment) were of moderate effect size (d = 0.38) and in the expected direction. CONCLUSIONS: DEMQOL-Proxy (self-administered) has comparable acceptability, reliability and validity with DEMQOL-Proxy (interviewer administered). DEMQOL-Proxy (self-administered) can be used in a wider variety of contexts than its interviewer-administered version, including routine use in busy clinics. Copyright © 2016 John Wiley & Sons, Ltd.

How does the EQ-5D perform when measuring quality of life in dementia against two other dementia-specific outcome measures?

PURPOSE: This study aimed to assess and compare the psychometric performance of the EQ-5D in relation to other dementia-specific measures, the QoL-AD and DEMQoL, within a psychosocial intervention study. METHODS: Two hundred and seventy-two people with dementia completed the EQ-5D, DEMQoL and QoL-AD. Convergent and discriminant validity of the measures were assessed, and inter-rater reliability was tested by comparing the self-reported and proxy scores of the measures. Internal consistency was tested using Cronbach's alpha. RESULTS: Results satisfy convergent validity amongst the three outcome measures. EQ-5D, DEMQoL and QoL-AD total scores were shown to be significantly correlated with each other (p < 0.001) in both participants with dementia and proxy reports. Results also satisfied discriminant validity for participant EQ-5D, DEMQoL and QoL-AD total scores. In relation to reliability between self and proxy scores, the EQ-5D showed higher reliability scores between participant and proxy total scores for mild and moderate level of cognitive impairment and performed better than the dementia-specific measures. Reliability assessed through Cronbach's alpha was satisfactory, indicating adequate internal consistency of all three measures. CONCLUSIONS: The results suggest that the EQ-5D might have advantages over other dementia-specific measures, and it could be used routinely and as a stand-alone measure of quality of life in dementia research.

The relationship between changes in quality of life outcomes and progression of Alzheimer's disease: results from the dependence in AD in England 2 longitudinal study.

OBJECTIVE: The relationship between conventional indicators of Alzheimer's disease (AD) progression and quality of life (QoL) outcomes is unclear. Dependence on others has been recommended as a unifying construct in defining AD severity. This study examined the relationship between indicators of disease severity (including dependence) and changes in QoL and utility over 18 months. METHODS: A multi-centre, cohort study was conducted across 18 UK sites. One hundred and forty-five patients with possible/probable AD and their caregivers completed assessments of disease severity (Dependence Scale, Mini-mental state examination, Neuropsychiatric Inventory, Disability Assessment for Dementia), dementia-specific QoL (DEMQOL, DEMQOL-Proxy) and generic health-related utility (EQ-5D) at both time points. RESULTS: There was evidence of individual change in QoL over 18 months, with over 50% of patients reporting either maintenance or improvement of life quality. The EQ-5D proxy suggested a mean decline in QoL, whereas the DEMQOL-Proxy indicated overall improvement. In the subsample of people who self-reported QoL and utility, no mean change was evident. Changes in dependence did not explain changes on any QoL or utility outcome. There was a weak association between the EQ-5D proxy and changes in cognition, whereas changes on the DEMQOL-Proxy were partly explained by changes in behavioural disturbance. CONCLUSIONS: The natural progression of AD over 18 months does not lead to inevitable decline in QoL or utility. There are no clear or consistent direct relationships between changes in disease severity and QoL outcomes. The impact of increasing dependence and worsening disease severity is likely buffered by a combination of psychological, social and environmental factors.

Feasibility of Routine Quality of Life Measurement for People Living With Dementia in Long-Term Care.

OBJECTIVES: Maximizing quality of life (QoL) is the ultimate goal of long-term dementia care. However, routine QoL measurement is rare in nursing home (NH) and assisted living (AL) facilities. Routine QoL measurement might lead to improvements in resident QoL. Our objective was to assess the feasibility of using DEMQOL-CH, completed by long-term care staff in video calls with researchers, to assess health-related quality of life (HrQoL) of NH and AL residents with dementia or other cognitive impairment. DESIGN: Cross-sectional study. SETTING AND PARTICIPANTS: We included a convenience sample of 5 NHs and 5 AL facilities in the Canadian province of Alberta. Forty-two care staff who had worked in the facility for ≥3 months completed DEMQOL-CH assessments of 183 residents who had lived in the facility for 3 months or more and were aged ≥65 years. Sixteen residents were assessed independently by 2 care staff to assess inter-rater reliability. METHODS: We assessed HrQoL in people with dementia or other cognitive impairment using DEMQOL-CH, and assessed time to complete, inter-rater reliability, internal consistency reliability, and care staff ratings of feasibility of completing the DEMQOL-CH. RESULTS: Average time to complete DEMQOL-CH was <5 minutes. Staff characteristics were not associated with time to complete or DEMQOL-CH scores. Inter-rater reliability [0.735, 95% confidence interval (CI): 0.712-0.780] and internal consistency reliability (0.834, 95% CI: 0.779-0.864) were high. The DEMQOL-CH score varied across residents (mean = 84.8, standard deviation = 11.20, 95% CI: 83.2-86.4). Care aides and managers rated use of the DEMQOL-CH as highly feasible, acceptable, and valuable. CONCLUSIONS AND IMPLICATIONS: This study provides a proof of concept that DEMQOL-CH can be used to assess HrQoL in NH and AL residents and provides initial indications of feasibility and resources required. DEMQOL-CH may be used to support actions to improve the QoL of residents.

A novel method of proxy reporting questionnaire based measures of health-related quality of life of people with dementia in residential care: a psychometric evaluation.

BACKGROUND: In research in residential care, health-related quality of life (HRQL) is usually measured using either observational methods or standardized questionnaires. DEMQOL-Proxy is a standardized questionnaire measuring HRQL of people with dementia and is usually reported by a family carer. However, not all residents have a family carer who visits often enough to act as a proxy. OBJECTIVES: We evaluated the psychometric performance of DEMQOL-Proxy when reported on behalf of people with dementia in residential care by a "trained proxy" (DEMQOL-Proxy-TP). PARTICIPANTS: We recruited a sample of 87 people with dementia living in care homes around the UK. METHODS: We used modern psychometric methods (based on the Rasch model) to evaluate DEMQOL-Proxy-TP (on behalf of 85 residents) in a cross-sectional study. We evaluated scale-to-sample targeting, ordering of item thresholds, item fit to the model and differential item functioning (sex, age, type of dementia), local independence, unidimensionality and reliability on the full set of items (31 items) and also a smaller item set (26 items). RESULTS: The smaller item set (DEMQOL-Proxy-TP-26) performed better than the original item set and was found to fit the model (p = 0.68). Nevertheless, 17 items were found to have disordered thresholds, and 24 pairs of items showed local dependency (residual correlations >0.3). There were also some areas where scale-to-sample targeting could be improved. CONCLUSION: After resolving the identified anomalies, DEMQOL-Proxy-TP can provide adequate measurement of HRQL of people with dementia living in residential care, particularly when no family carer is available. This can be interpreted at the group level but is not yet robust enough for use at the individual level. Future work will compare these results with the psychometric performance of DEMQOL-Proxy reported by family carers and DEMQOL self-reported by the residents.