Erasmus University Rotterdam
Institute of Health Policy and Management
(iBMG)
Franziska Beckebans
QoL in a German nursing home: Validation of ICECAP-O
Master’sThesis
Research paper to obtain the academic degree
M.Sc. in Health Economics, Policy and Law
(Specialization Health Economics)
1. Supervisor:
2. Co-Evaluator:
3. Co-Evaluator:
Peter Makai, M.Sc.
Renske Hoefman, M.Sc.
Saskia Schawo, M.Sc.
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Abstract
Purpose: To validate the German ICECAP-O version in a dementia-specific nursing home
as well as to assess if the capability measurement instrument ICECAP-O is a useful QoL
measurement instrument for people with dementia.
Method: For 80 residents, nursing proxy respondents completed proxy questionnaires.
These questionnaires included demographic questions, the QoL-measurement instruments
ICECAP-O, EQ-5D+C and ADRQL as well as the Barthel-Index for ADL. Convergent and
discriminant validity was investigated by correlating the tariffs and dimensions of the QoL
measurement instruments and the Barthel-Index with the ICECAP-O as well as through
regressions on the ICECAP-tariff with demographic and non-health related variables from
patients and proxy respondents.
Results: Our findings provide construct validity because of reasonable convergent and discriminant validity of the ICECAP-O. Convergent validity could be established by correlations between the ICECAP-O, the EQ-5D+C and the ADRQL dimensions as well as between the functional status score ADL. Discriminant validity was confirmed by differences
in the outcome of two groups of severity and functional status. The influence of the characteristics of the proxy respondents on the QoL measures was detected for single dimensions.
Discussion: In this pilot study in Germany, the ICECAP-O appears to be a reliable generic
QoL measurement instrument since results for validity are both convergent and discriminant. The results suggest that the ICECAP-O is a promising QoL measurement instrument
for dementia patients by assessing the capabilities of elderly people. The study is of importance for the economic evaluation of interventions for diseases, even though in Germany
only comparisons within one therapeutic area are practice. Further validation research is
needed to confirm the results of the study.
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Content
Abstract .............................................................................................................................. 2
Content .............................................................................................................................. 3
List of abbreviations ..........................................................................................................4
List of tables ...................................................................................................................... 5
1
Introduction ..............................................................................................................6
2
Methods ....................................................................................................................9
2.1
Setting ........................................................................................................9
2.2
Study population and data collection ......................................................... 9
2.3
Measures ..................................................................................................10
2.3.1
Demographic data ......................................................................10
2.3.2
ICECAP-O (ICEpop CAPablitiy measure for Older people) ....10
2.3.3
ADRQL (Alzheimer Disease Related Quality of Life) .............11
2.3.4
EQ-5D+C ...................................................................................11
2.3.5
Barthel - Index (BI) of Activities of Daily Living (ADL) .........12
2.4
Aim of the study and Hypothesis ............................................................. 13
2.5
Data analysis ............................................................................................ 14
3
Results .................................................................................................................... 15
3.1
Demographics and descriptive characteristics .........................................15
3.2
Convergent validity..................................................................................17
3.3
Discriminant validity ...............................................................................18
3.4
Regression results .................................................................................... 18
3.5
Further investigation of the proxies ......................................................... 19
4
Discussion ..............................................................................................................19
4.1
Main results .............................................................................................. 19
4.2
Methodological limitations ......................................................................20
4.3
Convergent validity..................................................................................21
4.4
Discriminant validity ...............................................................................22
4.5
Influences of proxy characteristics .......................................................... 23
4.6
German regulation for comparison across diseases .................................24
5
Conclusion .............................................................................................................24
References ....................................................................................................................... 26
Appendix ......................................................................................................................... 31
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List of abbreviations
ADL
ADRQL
EQ-5D+C
HrQoL
ICECAP-O
IQWiG
QoL
Activities of Daily Living
Alzheimer Disease Related Quality of Life
EuroQol five dimension + Cognitive Dimension
Health related Quality of Life
ICEpop CAPability measure for Older people
Institut für Qualität und Wirtschaftlichkeit im Gesundheitswesen
Quality of Life
4
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5
List of tables
Table 1
Table 3
Table 2
Table 4
Table 5
Demographic and description measurement instruments ....................... 16
Discriminant validity .............................................................................. 18
Convergent Validity ................................................................................ 33
Regression results ................................................................................... 34
Further investigation on the proxies ....................................................... 35
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6
Introduction
Currently around 1.3 million people suffer from dementia in Germany and this figure
is expected to reach almost 2 million by 2040 [1]. Due to this increase in the prevalence of
dementia, societies in developed countries will face a tremendous problem in the coming
decades. Increasing life expectancy leads to a rising number of people with dementia because of the higher risk of incidence with age [2]. Most patients receive informal care at
home, but with the current state of technology, institutional care is often inevitable as the
disease progresses and dependency on care increases [3]. Therefore about 60% of nursing
home residents in Germany already suffer from dementia and need to be cared for appropriately [4].
Because of strong economic pressure on compulsory health and long-term care insurance in Germany, economic evaluation recently became an important support for decisionmaking also for resource allocation of interventions and not only for drug therapies [5] [6].
For chronic diseases like dementia, Quality of Life (QoL) is an essential outcome measure
in economic evaluation. Generic QoL measurement instruments have the advantage that
they allow for comparison across diseases. In Germany however, in contrast to international
standards for health economic evaluation, the Institute for Quality and Efficiency in Health
Care (Institut für Qualität und Wirtschaftlichkeit im Gesundheitswesen, IQWiG), which
sets the official guidelines for health economic evaluation, suggests using the comparison
of QoL only within one therapeutic area and not across different diseases due to ethical and
methodological concerns [7]. This approach is questionable in times of rising economic
pressure on healthcare spending. With limited budgets, every allocation decision for one
disease has an impact on other diseases because alternative costs have to be considered.
Thus, if it is not possible to compare the beneficial impact of interventions on different
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therapeutic areas, the trade-off between interventions cannot be made because alternative
costs cannot be identified. Furthermore, equity problems may arise if decision makers decide in favour of a certain patient group because of higher need or larger group size, even if
the same intervention might have a better cost-benefit ratio for a different disease and patient group. Therefore, it is also worthwhile in Germany to carry out investigations that use
generic QoL-measurement instruments such as the ICECAP (ICEpop CAPability measure),
which compare economic evaluations across different diseases.
QoL measurement has the advantage that it captures different facets of people’s lives
rather than only health status or mortality [8]. Economic evaluation has traditionally assisted the allocation decision by assigning utilities to different health states to derive different
preferences, which was commonly done with the EQ-5D (EuroQol five dimension) [9]. But
QoL of older people, especially of those with cognitive impairments, depends not only on
generic assessed Health-related QoL (HrQoL), as measured by the EQ-5D, but also depends on other dimensions [10]. For example, people with dementia forget where they are,
lose their sense of time or do not recognize their own family members [11]. Usually they
are then corrected or reminded by nurses or relatives, making them feel ashamed and misunderstood, which undermines their sense of value. Additionally, people with dementia can
no longer fulfill their daily tasks in the way they could before, which leads to a decrease in
their social confidence and their feeling of being valued for who they are and for what they
do. Therefore, to ensure a sense of accomplishment and independence for dementia patients, other activities which match their abilities and remaining resources should be offered
in nursing homes [12]. Such emotional states and the participation in activities do not necessarily lead to an improvement in health but will increase the overall QoL through enjoyment of life. Generic measurement instruments such as the EQ-5D, which only takes
HrQoL into account, are therefore not sufficient for a complete economic evaluation. On
the other hand, a disease specific measurement instrument like the ADRQL (Alzheimer
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Disease Related Quality of Life) includes further aspects of patient’s life but does not take
into account physical health and does not allow for comparison across different diseases.
A relatively newly developed generic instrument, the ICECAP-O (ICEpop CAPability measure for Older people), seems to satisfy both requirements of economic evaluation
of diseases like dementia: it allows for comparison within and between therapeutic areas
and incorporates further aspects rather than only health. The capacity to carry out daily
tasks is of great importance for older people, as a reduction of ability limits their QoL [13].
Therefore the ICECAP-O measures Capability QoL and contains five attributes (attachment, role, enjoyment, security and control) [14] [15] [16]. Originally developed in the UK
to establish an index of capabilities for older people, validation studies confirmed that the
ICECAP-O evaluates a spectrum beyond HrQoL [17] [15]. So far, the ICECAP-O has been
used in the UK and amongst different proxy groups in the Netherlands [17] [15].
The choice for the setting of a dementia-specific nursing home with a sample of patients with cognitive impairments raises special challenges. At the stage of intermediate and
advanced dementia the disease affects cognitive abilities and people lack the capacity of
self-rating due to conditions such as the loss of memory, attention and language [18]. For
all instruments in this study, the proxy-report was used as suggested in the literature for
surveys in nursing homes among people with moderate to severe levels of cognitive disorders [19] [20] [21] [22] [23] [24].
The purpose of this study was to conduct a pilot to analyze the validity for the German version of the generic capability measuring instrument ICECAP-O for dementia.
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Methods
2.1
Setting
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The study was conducted in a specialized nursing facility for dementia in a mediumsized town in North Rhine-Westphalia, Germany1. The nursing home is devoted to the care
of people with dementia and is specially designed, in the shape of a figure eight at ground
level, to support the frequent need of movement for people with dementia. Residents can
walk around without getting lost and pass by the common room in the middle of the ‘eight’
where different activities are offered for participation or comfortable sitting corners encourage for relaxation [25].
2.2
Study population and data collection
The sample size included 80 residents with confirmed diagnosis of dementia from
one nursing home company with two separate buildings. All selected patients were over 55
and had lived in the nursing home for at least two month. The nurse, who takes care of a
patient at least four times a week and knows the patient for the longest time, was chosen as
proxy. This was determined by the head nurse who assigned a nurse to each resident as
proxy. In total, 8 nurses each answered between 4 and 20 questionnaires. All legal guardians were informed both in writing and orally about the study in advance. Only those residents were taken into account for whom there was an informed consent of a legal guardian.
To ensure privacy, the researcher did not see the name list of the residents at any time in the
study.
1
Pro8 – Lebensqualität für Menschen GmbH
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2.3
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Measures
2.3.1 Demographic data
Data on age, gender, marital status, duration of stay at the nursing home, frequencies of visits, care level and severity level of dementia were collected from the people with
dementia living in the nursing home. For clinical data, dementia was diagnosed by the general practitioner as well as type according to the ICD-10 (F00.-, F01.- or F02.-) [26] and
severity of dementia according to the German guideline for dementia [27]. For proxies, data
on age, role, length of employment and length of time the nurse knew the resident were
collected.
2.3.2 ICECAP-O (ICEpop CAPablitiy measure for Older people)
The ICECAP-O (ICEpop CAPablitiy measure for Older people) 2 is a relatively newly developed QoL measurement instrument of capabilities of older people for use in economic evaluation. Derived from Sen’s capabilities approach [14] [28], the instrument was
originally developed to provide a set of general capability values of the UK population over
65, using best-worst scaling, a special type of Discrete Choice Experiment (DCE) [29]. The
index of capabilities has five attributes (attachment, security, role, enjoyment and control)
each with four levels, which may result in 1024 health states in total [30] [31]. So far, the
construct validity for the ICECAP has been confirmed in a British and a Dutch study on
proxies [15] [32]. For the first use of the ICECAP-O in Germany, the questionnaire was
forward-backward translated from English into German by two independent translators.
In order to compute capability values, the British tariffs were applied because these
do not exist for Germany.
2
Previously called ICECAP [29].
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2.3.3 ADRQL (Alzheimer Disease Related Quality of Life)
We used the revised 40-Item version of the Alzheimer Disease Related Quality of
Life (ADRQL) instrument in this study, which allows for the assessment of QoL for people
at intermediate or late-stage dementia because of proxy-report [24] [33] [34] [35] [36].
Especially developed for people with dementia, the multi-dimensional QoL instrument ADRQL can be assessed by family or professional caregivers [37] [38] [8] [39]. The
ADRQL offers a comprehensive QoL assessment across the following five domains [38]:
Social Interaction, Awareness of Self, Enjoyment of Activities, Feelings and Mood, Response to Surrounding. The dichotomous response option for the caregiver is agree or disagree for the behaviour of the persons with dementia in the last two weeks. The various domains range from 4 to 12 items and each item is scored in a range from 9.15 to 13.75, based
on a judgment of importance by caregivers [40]. For each domain a separate subscale can
be calculated and finally summed up in one total score for each resident which ranges from
0 (lowest quality of life) to 100 (highest quality of life) [41]. As suggested in several studies the instrument exhibits good psychometric properties having adequate validity, good
internal-consistency reliability, very low missing data and sensitivity to change [42] [43].
The printed version of the authorized German edition of the ADRQL was used [39].
2.3.4 EQ-5D+C
The EQ-5D is a commonly used generic HrQoL measurement instrument, developed by the EuroQol group [44]. The instrument allows for the comparison of a wide range
of health states and has two components: the descriptive system and a visual analogue
scale. [44]. In this study only the descriptive component was used.
For its use in dementia, the EQ-5D was extended for a cognitive dimension
[45][46]. The health index component of the EQ-5D+C is therefore made up of six dimen-
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sions: mobility, self-care, usual activities, pain/discomfort, anxiety/depression and additionally cognition. Each dimension has three levels: no problems, some problems, extreme
problems [47] [9]. In this study the official German proxy version 2 of the EQ-5D was used
and the own translation of the cognitive dimensions was added [48]. The visual analogue
scale was not included because of reported problems in the use for dementia from other
studies and its primary intention for self-rating [21]. Resulting in a total of 243 possible
health states, the result of the original EQ-5D can be converted to a utility score by applying the German EQ-5D index based on TTO values by Greiner et al. [49] [50].
2.3.5 Barthel-Index (BI) of Activities of Daily Living (ADL)
The Barthel-Index is a well-established instrument that measures the functional status by the patients’ ability to perform Activities of Daily Living (ADL) by proxy- or selfreport. The tool includes items such as personal toilet, moving from wheelchair to bed and
back or walking on level surface. Valuated using four categories (unable (0), needs minor
or major help (5/10) and independent (10/15)) the total achievable score ranges between 0
and 100, where a higher score indicates a higher independence in the ability to perform
ADL [51] [52]. According to the phases of neurological care, an index between 70 and 100
indicates independence with some restrictions and an index below 65 indicates the need for
care in daily life [53].
The ADL-score is mainly used in geriatric fields and is a strong predictor of QoL
scores across several outcome measurements, including the ADRQL [35] [54]. In this study
the German version was applied with some terms adapted and changed [55].
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2.4
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Aim of the study and Hypothesis
The aim of the study is to explore to what extent the German version of the capability
measuring instrument ICECAP-O assesses the QoL of persons with dementia in long-term
nursing homes.
For the test of convergent validity in this setting, it is expected that the results for
QoL from the ICECAP-O are associated with the results of the dementia-specific measurement instrument ADRQL. For the comparison between the ICECAP-O and the EQ-5D results, a correlation in the same direction is expected, but smaller than for the ADRQL, because the generic EQ-5D measures HrQoL without disease specific questions and does not
take behaviour into account. We expect that single dimensions of the ADRQL and EQ-5D
will be stronger correlated with the ICECAP-O capability dimensions than others. The outcome of the ICECAP-O is expected to associate with the ability to perform ADL as one of
the visible manifestations of dementia for progressive inability to perform daily activities
and the subsequent loss of independence [56]. For that reason a significant correlation is
hypothesized between the measures for the Barthel-Index of ADL and the results for the
ICECAP-O.
For discriminant validity we expect to find deviations in the QoL measures of different instruments between two groups for dementia severity (mild/moderate and severe) and
between two groups for people with different ADL-scores (< 65; ≥ 65). Thereby, a higher
score of QoL is assumed for the better-off groups. In a multiple regression we suggest that
the capability measurement of the ICECAP-O assesses a concept broader than only health,
as measured by the EQ-5D. Therefore, apart from variables of physical health, variables of
mental health or demographic variables, other characteristic variables from residents are
also presumed to be related to the ICECAP tariff.
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It is questionable as to how far the measures in this study are influenced by the different characteristics of the proxies, as observed in several studies [41] [23]. It is hypothesized, that an influence of the characteristics of the proxy respondents like age, role and
time knowing the patient on the QoL measurements will be different for more and less observable dimensions.
2.5
Data analysis
The demographic characteristics of residents and proxies were analyzed using de-
scriptive statistics. Mean, standard deviation or median was computed of demographic data
of the residents and for the different dimensions of the QoL-measurement instruments.
Reliability and internal consistency of the ADRQL were analyzed using Cronbach’s
Alpha statistics. Correlations between the outcomes of the ICECAP-O and dimensions of
the ADRQL, EQ-5D and the ADL were used to estimate the convergent validity. Two severity groups mild/moderate and severe were formed in order to assess discriminant validity and to observe whether the severity of dementia does in fact influence the QoL. For those
two severity groups discriminate validity was analyzed using T-test or Mann-Whitney-U
test on the tariffs of the measurement instruments used in this study. The same was done for
the Barthel-Index of ADL, with one group above and another group below the index of 65,
when care in daily life activities is needed.
To evaluate whether the ICECAP-O measures a broader concept than HrQoL, as
measured by the EQ-5D, a multiple regression was performed with a control for demographic and care related variables. For the observations of changes in coefficients and significance levels, the QoL measurement instruments and different characteristics of the
proxies were added incrementally to the regression model.
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Additionally, the influence of the characteristics of the proxies such as age, role and
the time knowing the residents on the different dimensions of the ICECAP-O, EQ-5D+C
and ADRQL were investigated using ordered logistic regression.
There was no missing data, so there was no need to correct for this in the study. For
all analysis the level of significance was p < 0.05. Data was analyzed using STATA 11.
3
Results
3.1
Demographics and descriptive characteristics
Data were collected between May and August 2011. In total, eight different nurses
as proxy respondents filled out questionnaires for 80 residents of the specialized nursing
home in North Rhine-Westphalia, Germany. Descriptive statistics were presented for the
demographic and care-related characteristics of the residents and for the tariffs of the QoL
measurement instruments and their dimensions in Table 1.
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Table 1 Demographic and description measurement instruments
Demographics
Age
Sex
Type of dementia
Residents (n=80)
77.15 (8.41)
58.8% female
62.5 % (0.71) with Alzheimer
Severity level of dementia
mild
moderate
severe
5%
36.3%
58.8%
Months living in nursing home
0 ≤ 6 months
6 ≤ 12 months
12 ≤ 24 months
> 24 months
Martial Status
unmarried
married
divorced
widowed
Frequency of visits²
more often than once a week
less than once a week
Care Level
Level 1
Level 2
Level 3
ICECAP-O
Attachment
Security
Role
Enjoyment
Control
ICECAP Tariffs
EQ-5D+C
Mobility
Self-Care
Usual activities
Pain/Discomfort
Anxiety/Depression
Cognition
EQ-5D Tariffs
ADRQL (Original weights)
Social Interaction (SI)
Awareness of Self (AS)
Feelings and Mood (FM)
10%
13.8%
18.8 %
57.5%
20%
22.5%
16.3%
41.3%
35%
65%
15%
32.5%
52.5%
2.83 (0.73) 3
3.20 (0.70) 3
2.05 (0.91) 2
2.74 (0.74) 3
1.72 (0.83) 1
0.62 (0.20)
1.85 (0.87) 2
2.56 (0.57) 3
2.51 (0.57) 3
1.41 (0.57) 1
1.18 (0.44) 1
2.73 (0.45) 3
0.48 (0.34)
73.96 (25.08) 75.79
47.08 (28.70) 39.04
84.42 (16.62) 85.03
16
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Enjoyment of Activities (EA)
Response to Surroundings (RS)
Overall ADRQL
Barthel-Index (ADL)
Overall ADL
Index below 65
Index above 65
17
50.44 (29.92) 49.62
91.01 (17.28) 99.99
70.93 (14.82) 71.81
38.94 (29.40) 45
76.25%
23.75%
Mean (Standard devation) Median
² 7.5% of all residents never get visits
3.2
Convergent validity
In Table 2 the correlations between the tariffs of the ICECAP-O and the tariffs of
the EQ-5D, ADRQL and the ADL are shown. Correlations on tariffs were particularly
strong between the ICECAP-O and the EQ-5D and ADL.
For the detailed observations of convergent validity each tariff and each dimension
were correlated with each other. Among these correlations, predominantly significant results can be observed between the ICECAP-O tariff and the different dimensions of the EQ5D+C and the ADRQL, except for the dimension “anxiety” (EQ-5D+C) and the dimensions
“Feeling and Mood” (FM) and “Response to the Surroundings”(RS) (ADRQL). The dimension “attachment” of the ICECAP-O was significantly correlated with all dimensions of the
other instruments, except for “pain” and “cognition” of the EQ-5D+C and FM and RS of
the ADRQL. The ICECAP-tariff “security” on the other hand was mostly not significant
and when it was, the significance was only slight with regard to “anxiety” (EQ-5D+C), FM
and RS (ADRQL). All dimensions of the EQ-5D+C, with the dimension of “anxiety” being
the only exception, showed significant correlation with the ICECAP-O dimension “role”.
The same applies for the dimensions of the ADRQL, except for FM and RS. The ICECAPO dimensions “enjoyment” and “control” are significantly correlated with most of the other
dimensions, even if the association for “enjoyment” was weaker than for “control”.
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A higher level of the Barthel-Index of the ADL was always correlated with a higher
score of each single dimension, except for “security” (ICECAP-O), “anxiety” (EQ-5D+C) ,
Social Interaction (SI), FM and RS (ADRQL).
3.3
Discriminant validity
Severity of the disease played a significant role for most of the variables and dimen-
sions. The results of the T-tests for the ICECAP-O and ADRQL tariff and the results of the
Mann-Whitney-U test for the EQ-5D tariff in Table 3 confirmed that there is a significant
discrepancy between different severity (mild/moderate, severe) and ADL (< 65; ≥ 65) subgroups, when used as dummy variables. As expected, for all three instrument tariffs a lower
score for the more severe and less functional group can be observed.
Table 3 Discriminant validity
Severity
mild/moderate
severe
mean (SD)
mean (SD)
P-value
EQ-5D
0.781 (0.24)
0.285 (0.24)
0.000**
ICECAP-O
0.771 (0.15)
0.522 (0.16)
0.000**
ADRQL
ADL-Barthel Index
78.731 (12.89)
65.449 (13.69)
0.000**
below 65
above 65
mean (SD)
mean (SD)
P-value
EQ-5D
0.366 (0.29)
0.887 (0.11)
0.005**
ICECAP-O
0.569 (0.19)
0.803 (0.13)
0.000**
79.05 (14.47)
0.000**
ADRQL
69.40 (14.11)
**significance on the 1% level
3.4
Regression results
Table 4 shows the results of the incremental expansion of the multiple regressions
on the ICECAP-O tariff. A relatively weak, but significant association can be observed
with the ADL and the ADRQL, but not with the EQ-5D. Furthermore, showed the duration
of time residents lived in the nursing home a relationship with the ICECAP-O tariff on the
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5% level of significance. By adding the characteristics of the proxies to the regression, the
variable of the number of months a nurse takes care of the resident shows a slightly negative influence on the 5% significance level.
3.5
Further investigation of the proxies
To investigate the influences of the different proxy characteristics on the single di-
mensions of the measurement instruments, ordered logistic regressions were applied. Results are shown in Table 5. Only role of the nurse in the nursing home and the time the
nurse knew the patient showed significant influences. Role of the nurse had a negative impact on the dimensions “security”, “enjoyment” (ICECAP-O) and “Feelings and Mood”
(FM) (ADRQL), and a positive impact on “anxiety” (EQ-5D+C). Duration of time knowing
the resident had a significant positive influence on the dimension of FM (ADRQL).
4
Discussion
4.1
Main results
In our study the ICECAP-O was applied for the first time in Germany in a disease-
specific nursing home for dementia. The significant correlations between the ICECAP-O
tariff, the EQ-5D tariff and the ADRQL tariff as well as between the ADL score confirmed
the hypothesis of convergent validity. But different than hypothesized, the correlation between the ICECAP-O tariff and the health measuring EQ-5D tariff was stronger than the
correlation between the dementia measuring ADRQL tariff. As in general expected, single
dimensions were more strongly related to the ICECAP-O than others.
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As noted earlier, all QoL measurement instruments applied in this study were expected to significantly discriminate between the two groups of severity (mild/ moderate and
severe) and ADL-status (<65; ≥ 65). The findings for the differences in the overall scores of
the QoL measurement instruments among subgroups supported discriminant validity.
The correlation results, together with the significant influence of non-health related
dimensions on the ICECAP-O in the multiple regression, provide support that the ICECAPO measures dimensions relevant for people with dementia and therefore a broader spectrum
than only health, as measured by the EQ-5D. However, one variable which was significant
in the correlations were no longer significant in the regression.
The test for the effects of the proxy-report on the results showed a significant influence of some proxy characteristics on single dimensions of the QoL measurement.
4.2
Methodological limitations
Our results cannot be generalized by implication because of some methodological
limitations, which are worth considering. First, the residents for this study were not randomly selected and therefore might have characteristics that differ from the typical population with dementia in German nursing homes. However, this restriction may only influence
the results to a certain extent, because the focus of the study was the validation of the properties of the QoL measurement instruments and not their measurement results. In addition,
the relatively small-scale of the study can be seen as a methodological limitation and a bigger sample size might have led to more reliable results.
Another limiting aspect is the use of only the nurse rather than many different
proxies, because family members or spouses have diverse viewpoints on the health and
capabilities dimensions of a patient [23]. But in a nursing home, the responsible nurse does
have the most contact with the patient and observes physical and mental conditions in all
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21
situations of life and not only during visiting hours. Therefore, in this care setting using
only the nurse as proxy respondent does seem to be the logical choice as already examined
previously [15].
In this study, British tariffs were used for the ICECAP-O since German tariffs
are not yet available. For this reason, results may be imprecise because weights for capability dimensions might vary between countries. American tariffs were applied for the
ADRQL, since the only existing German tariffs, set by a Swiss study of Menzi-Kuhn, did
not deliver different results [39].
4.3
Convergent validity
The finding of the strong correlation between the ICECAP-O dimensions and the
EQ-5D dimensions shows that physical health is captured to a wide extent by the ICECAPO capability measurement, what is especially important in studies of elderly. But the fact,
that the results also confirm the expected significant correlation between the ICECAP-O
and the ADRQL tariffs, shows that the ICECAP-O captures both, the physical health as
well as dementia related dimensions.
The expected significant positive correlation of the ADL-status with all ICECAP-O
dimensions, except for “security”, reflects a decline of QoL through the loss of independence in daily activities. This correlation is strengthened by the same finding for the other
applied QoL measurement instruments in this study.
As an exception to the other dimensions, the ICECAP-O dimension “security”
showed almost no significant correlation with the dimensions of the other QoL measures.
The same finding was observed in the Dutch ICECAP-O validation study in which also no
correlation with the dimension “security” was found [15]. This might be because people
living in a nursing home do not worry about the future up to a certain point, because the
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22
nursing home resembles a safe environment, as was hypothesized by Makai et al. [15]. As
described in the introduction of this paper, not only health but also capability dimensions
are of special relevance for the QoL of people with dementia. The moderately to highly
significant correlations of the capability dimensions “enjoyment”, “role” and “control” with
the ADRQL and the EQ-5D dimensions, support the hypothesis that the ICECAP-O captures dimensions are relevant for the elderly. Such correlations with the EQ-5D were also
found in the general British population [32]. One also sees that the dimensions “Feelings
and Mood” (FM) and “Response to surrounding” (RS) of the ADRQL do not correlate with
any ICECAP-O dimensions. Therefore, another explanation might be more adequate. Both
dimensions enquire about behaviours like crying, hitting, resisting help, talking about leaving or the wish to die, none of which are directly related to the capabilities of a person and
therefore almost no significant correlation with the ICECAP-O dimensions can be observed. Furthermore, the ICECAP-tariffs of “enjoyment” and “attachment” are neither correlated with the cognitive dimension nor the pain dimension of the EQ-5D+C. One reason
for this might be the less observable feature of the dimension “attachment” and “enjoyment” for the proxy respondent. Another explanation could be that the cognitive status does
not influence the joy people can still have in their lives and pain does not affect the amount
of love someone receives.
4.4
Discriminant validity
It was not surprising that the results of the different overall QoL measures in this
study discriminated between the severity and ADL-status subgroups, because all instruments measure health. Therefore the group of healthier residents and the group with a higher functional status also reached the expected higher tariff scores. These significant findings
confirm that reasonable discriminant validity exists.
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23
Even if strong significance was given for severity of dementia on all capability dimensions of the ICECAP-O in the correlation and in the test for discriminant validity, contrary to expectations, severity did not show significant influence in the multiple regression
on the ICECAP-O tariff. A plausible explanation for this might be that severity of dementia
influences the ADL-status and this strong relationship exceeded the significance of severity
and therefore the variable severity has become insignificant in the regression. The differences between the severity and the ADL-status groups in the tests for discriminant validity
support this assumption and add more weight in favor of construct validity for the German
ICECAP-O version.
4.5
Influences of proxy characteristics
Proxy-report matters in the measurement of QoL, as it has already been observed in
other studies [23] [15] [19] [57]. Also in our study, the characteristics of the proxy respondents influenced the QoL measures differently on their more or less observable dimensions. The highly negative significance of the dimensions “security”, “enjoyment” and FM
for the role of the proxy might be an indication for a worse judgment on these less observable dimensions the higher the role of the nurse. This is reasonable as, in general, the higher
the role, the less the “on the bed” care contact with residents and the less the experience
with these more subjective dimensions of the patient. The positive influence of the dimension “anxiety” of the EQ-5D for role might be explained by the fact that, apart from anxiety, the question also asks about how depressed a person is and this might be less exactly
judged the higher the role of a nurse because of less intimate and intensive contact to the
resident. The time of knowing the patient is positively correlated with FM of the ADRQL,
which supports the better judgment of a proxy of less observable dimensions the longer
people know each other, especially in a nurse-patient relationship.
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24
In the regression, the number of month a proxy respondent knows the patient had also a significant influence on the ICECAP-O tariff. This finding suggests that the time
knowing the person, for whom the proxy answered the questions, influences the responses
on the ICECAP-O, at least in our case for people with dementia.
4.6
German regulation for comparison across diseases
The regulations of the IQWiG for economic evaluation are criticized for their devia-
tion from common health economic methodology [58] [59] [60] [61]. This criticism comes
from national and international researchers, physicians, scientific associations and as well
as from the pharmaceutical industry in Germany. On the one hand, making comparisons
across diseases is needed to make reasonable decisions on the allocation of resources across
different therapeutic areas. On the other hand, the IQWiG argues that comparisons across
different diseases will never be perfect and therefore the results will not be completely reliable or fair [58] [59]. But, as a result of economic pressure on the health and care system,
the economic evaluation needs to be extended for generic QoL measurement instruments.
This is needed to ensure a more equitable and a more economic decision in terms of alternative costs. The economic evaluation across diseases with generic QoL measurement instruments could also support the decision processes in Germany. Therefore, in this study, a
generic QoL measurement instrument was validated and applied in Germany even though it
is not yet practice there.
5
Conclusion
The German version of the ICECAP-O was applied for the first time in this pilot
study and appears to be a reliable QoL measurement instrument based on the results for
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25
convergent and discriminant validity. The results of the correlations between the ICECAPO dimensions and the dimensions of the other QoL-measurement instruments together with
the influences of other variables than health related variables in the regression, confirms
that the ICECAP-O is a suitable QoL-measurement instrument for people with dementia.
The influence of the characteristics of the proxy such as the role of the nurse and the time
the proxy respondent knows the patient suggests that additional research on these proxy
groups is needed to confirm these findings.
Recognition of the validity of the ICECAP-O as a generic QoL measurement instrument, which allows for comparison across diseases, might provide a further contribution to the discussion in health economic evaluation on comparison across diseases in Germany. This seems to be especially relevant for informed decisions in the health and care
sector because of the growing number of elderly people with dementia and the expected
increase in costs.
Further validation studies, apart from this pilot, are needed to strengthen the construct validity of the ICECAP-O for its use in Germany. In particular, its application in different settings with bigger sample-groups would reinforce the results of this study.
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26
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Appendix
German version of the ICECAP-O (Original from © Joanna Coast & Terry Flynn) [31]
1. Liebe und Freundschaft
Der Bewohner kann all die Liebe und Freundschaft haben, die er will
4
Der Bewohner kann viel von der Liebe und Freundschaft haben, die er will
3
Der Bewohner kann nur wenig von der Liebe und Freundschaft haben, die er will
2
Der Bewohner kann keinerlei von der Liebe und Freundschaft haben, die er will
1
2. Gedanken über die Zukunft
Der Bewohner kann über die Zukunft ohne Sorgen nachdenken
4
Der Bewohner kann mit wenig Sorgen über die Zukunft nachdenken
3
Der Bewohner kann über die Zukunft nur mit einigen Sorgen nachdenken
2
Der Bewohner kann über die Zukunft nur mit großen Sorgen nachdenken
1
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32
3. Dinge tun, durch die ich man sich geschätzt fühlt
Der Bewohner ist in der Lage alle Dinge zu tun, durch die er sich geschätzt fühlt
4
Der Bewohner ist in der Lage viele Dinge zu tun, durch die er sich geschätzt fühlt
3
Der Bewohner ist in der Lage einige Dinge zu tun, durch die er sich geschätzt fühlt
2
Der Bewohner ist nicht in der Lage irgendwelche Dinge zu tun, durch die er sich geschätzt fühlt
1
4. Freude und Vergnügen
Der Bewohner kann all die Freude und das Vergnügen haben, die er will
4
Der Bewohner kann viele der Freuden und Vergnügen haben, die er will
3
Der Bewohner kann nur wenig der Freuden und Vergnügen haben, die er will
2
Der Bewohner kann keinerlei Freude und Vergnügen haben, die er will
1
Der Bewohner ist in der Lage, völlig unabhängig zu sein
4
Der Bewohner ist in der Lage, in vielen Dingen unabhängig zu sein
3
Der Bewohner ist in der Lage, in einigen Dingen unabhängig zu sein
2
Der Bewohner ist nicht in der Lage, unabhängig zu sein
1
5. Unabhängigkeit
33
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Table 2 Convergent Validity
ICECAP ICECAP
ICECAP
EQ5D EQ5D EQ5D
EQ5D EQ5D
Attach- SeICECAP EnjoyICECAP Mobi- SelfAcEQ5D AnxCogADRQL ADRQL ADRQL ADRQL ADRQL
ment
curity
Role
ment
Con-trol lity
care
tivity Pain
iety
nition SI
AS
FM
EA
RS
n=80
ICECAP ADRQL EQ5D ADL
1.00
ICECAP
0.53**
1.00
ADRQL
0.70**
0.43**
1.00
EQ5D
0.77**
0.48** 0.91**
1.00
ADL
ICECAP
0.58**
0.46** 0.29** 0.33**
1.00
Attachment
ICECAP
0.12
0.11 - 0.12 - 0.06
0.19
Security
ICECAP
0.81**
0.48** 0.72** 0.79**
0.43**
Role
ICECAP
0.69**
0.52** 0.38** 0.44**
0.71**
Enjoyment
ICECAP
0.79**
0.30** 0.66** 0.72**
0.11
Control
EQ5D
0.67**
0.33** 0.85** 0.86**
0.24*
Mobility
EQ5D
0.60**
0.35** 0.85** 0.79**
0.31**
Selfcare
EQ5D
0.60**
0.27** 0.67** 0.70**
0.30**
Activity
0.22*
0.11 0.49** 0.35**
-0.02
EQ5D Pain
EQ5D
0.17
0.33**
0.13
0.12
0.30**
Anxiety
EQ5D+C
0.47**
0.41** 0.58** 0.62**
0.12
Cognition
0.42**
0.83** 0.22*
0.25
0.41**
ADRQL SI
ADRQL
0.55**
0.65** 0.58** 0.63**
0.35**
AS
ADRQL
0.03
0.53**
0.02
0.04
0.10
FM
ADRQL
0.40**
0.60** 0.42** 0.42**
0.32**
EA
ADRQL
0.05
0.11
-0.05
0.01
0.13
RS
*significance on the 5% level, **significance on the 1% level
1.00
- 0.02
1.00
0.18
0.58**
1.00
- 0.12
0.64**
0.29**
1.00
- 0.07
0.64**
0.37**
0.60**
- 0.16
0.61**
0.25*
- 0.12
0.05
0.61**
0.29**
0.30**
0.16
0.24*
0.08
0.32**
- 0 .11
0.17
0.54**
0.32**
- 0.21
1.00
0.61** 0.58**
1.00
0.61** 0.51** 0.73**
0.24* 0.41**
0.17
1.00
0.24*
1.00
-0.16
0.21
0.20
0.44**
0.55** 0.42** 0.65** 0.59**
0.21
0.20
0.16
0.12
0.14
- 0.01
0.01
1.00
0.22* 0.28**
1.00
0.59**
0.40**
0.47** 0.42** 0.57** 0.46**
0.08
0.14 0.51**
0.36**
1.00
0.25*
0.00
0.17
-0.05
0.15
0.19
0.08
0.26*
0.01
1.00
- 0.13
**0.36
0.31**
0.25* 0.33** 0.38** 0.30**
0.09
0.24* 0.28**
0.42**
0.39**
0.11
1.00
0.43**
0.05
0.19
-0.11
0.10 0.44**
- 0.04
- 0.16
0.29**
- 0.03
-0.03
-0.09
0.10
-0.02
0.00
-0.04
-0.04
-0.13
-0.12
1.00
-0.12
1.00
34
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Table 4 Regression results
ICECAP-O
Beta
SD
P-value
Severity
-0.027
0.034
0.420
Age
-0.000
0.002
Gender
0.030
Livingtime
Beta
SD
P-value
Beta
SD
P-value
Severity
-0.014
0.033
0.684
Severity
-0.018
0.032
0.581
0.961
Age
-0.000
0.002
0.976
Age
-0.001
0.002
0.674
0.035
0.394
Gender
0.015
0.034
0.665
Gender
0.029
0.036
0.391
0.033
0.017
0.053*
Livingtime
0.036
0.016
0.028*
Livingtime
0.045
0.018
0.014**
Marital
-0.007
0.014
0.588
Marital
-0.000
0.013
0.991
Marital
-0.019
0.014
0.185
Type of Dementia
0.014
0.034
0.679
Type of Dementia
0.014
0.033
0.679
Type of Dementia
0.016
0.032
0.609
Visits
0.008
0.035
0.829
Visits
0.030
0.035
0.395
Visits
0.006
0.035
0.859
Carelevel
0.011
0.028
0.703
Carelevel
0.028
0.028
0.329
Carelevel
0.032
0.028
0.247
+ ADL
0.005
0.001
0.000**
ADL
0.005
0.001
0.001**
ADL
0.006
0.001
0.000**
+ EQ5D
-0.006
0.107
0.954
EQ5D
-0.035
0.104
0.738
+ ADRQL
0.003
0.001
0.010**
ADRQL
Proxy characteristics
0.004
0.001
0.002**
+ Age
0.002
0.001
0.119
+ Role
0.037
0.030
0.223
+ Months known
-0.002
0.001
0.040*
* significance on the 5% le
** significance on the 1% level
ICECAP-O
ICECAP-O
35
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Table 5 Further investigation on the proxies
O-logit
Dimensions
Age
Role
Time
Attachment
0.03 (0.20) 0.136
1.28 (0.47) 0.006
-0.00 (0.11) 0.817
Security
-0.01 (0.02) 0.484
-1.81 (0.50) 0.000 **
-0.02 (0.01) 0.133
Role
0.00 (0.01) 0.795
0.17 (0.41) 0.676
0.00 (0.01) 0.793
Enjoyment
0.01 (0.18) 0.496
-0.87 (0.44) 0.050 *
0.00 (0.01) 0.594
Control
0.01 (0.02) 0.401
0.40 (0.43) 0.354
0.00 (0.01) 0.671
Mobility
0.01 (0.02) 0.529
-0.05 (0.42) 0.902
0.00 (0.01) 0.548
Selfcare
-0.02 (0.02) 0.408
0.36 (0.46) 0.439
0.00 (0.01) 0.929
Activity
-0.03 (0.02) 0.122
0.40 (0.46) 0.388
0.00 (0.11) 0.913
Anxiety
-0.01 (0.03) 0.661
2.29 (0.84) 0.006 **
-0.04 (0.03) 0.137
Remember
-0.03 (0.02) 0.176
0.01 (0.50) 0.977
-0.01 (0.01) 0.349
Social Interaction (SI)
0.01 (0.02) 0.701
-0.44 (0.41) 0.277
0.01 (0.01) 0.147
Awareness of Self (AS)
-0.01 (0.02) 0.751
0.02 (0.39) 0.965
0.01 (0.01) 0.513
Feelings and Mood (FM)
0.01 (0.02) 0.747
-0.95 (0.42) 0.023 *
0.03 (0.01) 0.004 **
Enjoyment of Activities (EA)
0.01 (0.02) 0.692
-0.16 (0.39) 0.676
0.01 (0.01) 0.586
Response to Surroundings (RS)
0.01 (0.02) 0.809
-0.65 (0.51) 0.200
0.00 (0.01) 0.837
Instrument
ICECAP-O
EQ5D+C
ADRQL
Coefficient (SD) P-value
* significance on the 5% le
** significance on the 1% level