Systematic Reveiw Huntingtons disease

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Lay Abstract
Huntington’s disease (HD) is a relatively rare genetic neurological condition.
Despite its relatively low occurrence in the general population, it has a
substantial impact on its victims. The effect of HD can easily be seen,
because suffers have difficulty with general cognitive functions and physical
actions such walking and eating food. These debilitating symptoms increase
emotional social and economic impact of HD.
Health state values help health economist to calculate the socioeconomic
impact of a disease on an individual. Little is known about the health state
values of HD. Health state values are needed to calculate the Quality
Adjusted live Years (QALYs). QALYs are used by organisations such as
National Institute of Clinical and Health Excellence (NICE) to measure the
cost and benefits of new and old innovations in healthcare. The QALY
combines the impact an innovation can have on a person’s quality of life, and
quantity of life into one numeric value. A systematic literature review, that
could easily be replicated (Systematic Review) was conducted to identify the
health state values for HD in the published literature.
Only two papers matched the inclusion and exclusion criteria that were set.
The two papers were Hocoaglu et al (2012) and Calvert et al (2012). They
reported and EQ-5D mean score of 0.3 and 0.53 respectively. The EQ-5D is a
generic measure used to gather health state values from the general public.
Hocoaglu et al (2012) reported a VAS score of 58.4. VAS (Visual Analogue
Scale) is a generic measure used to gather health state values from
individuals who have a particular condition. The ability of the EQ-5D to
measure the health state values of people with HD was also investigated.
Some weaknesses were found in the methods used to gather health state
values; this suggests a need for further research in this area.

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Abstract
Introduction: Huntington’s disease (HD) is a genetic
neurodegenerative condition. It is relatively rare, but its impact on a
person’s health related quality of life (HRQoL) can be substantial.
Health state values are used as weights to calculate the quality
adjusted life years (QALYs) and could be used by policy makers to
develop suitable policies for people living with HD. A systematic review
of published literature was conducted to identify the health state values
for people who have been diagnosed with HD.
Method: A systematic search was conducted in accordance with the
PRISMA guidelines to find the current literature on the health state
values of individuals with HD. The included articles were critically
appraised.
Results: Two articles were identified, at the end of the systematic
search, they were: Calvert et al (2012) and Hocaoglu et al (2012). The
authors used the EQ-5D to report health state values, for individuals
who were diagnosed with HD. They reported mean scores of 0.3 and
0.53 respectively. Hocaoglu et al (2012) reported a VAS score of 58.4.
A critical analysis was carried out on the methods used to gather the
health state values.
Conclusion: Two full articles matched the inclusion criteria. On the
basis of the critical analysis, recommendations were made to improve
the methods that researchers used to investigate the health state
values of individuals who had HD. The results suggest that EQ-5D
lacked content validity as a measure for the HRQoL in the lives of
people with HD. Additional research is needed to provide health state
values for each level of disease severity. The HDQoL could be
developed as a condition-specific preference-based measure.

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Background
According to Haskins et al (2000), the clinical features of Huntington's
disease (HD) were first described in the 19th century by George
Huntington. Fiedorowicz et al (2011) described HD as a fatal
neurodegenerative condition that affects many parts of the brain. It
occurs due to an excessive number of CAG repeats on chromosome
four. The prevalence of HD has been estimated by Pringsheim et al
(2012) to be 5.7 per 100,000 in North America, Europe and Australia.
Since HD follows an autosomal dominant pattern of inheritance,
individuals with the defect have a 50% chance of passing the disease
to their children. Cases of people with the disease are likely to increase
in the future (Walker et al 2007). Chisholm et al (2012) and Evans et al
(2010) have shown that characteristic of HD is that it is fully penetrant,
therefore people who test positive for HD in a genetic test would
definitely develop the disease in the future; even if they did not exhibit
the symptoms before testing. Disease onset usually occurs when
individuals are in their forties and the average life expectancy is 15 to
25 years after diagnosis (Walker 2007).
Studies have shown that HD causes an individual’s motor, cognitive
and behavioural functions to decline over time, until the individual
becomes fully dependent on care (Walker et al 2007; Fiedorowicz et al
2011 and Veenhuizen et al 2011). According to Carlozzi et al (2012);
Beglinger et al (2007) and Haskins et al (2000), patients may suffer
from psychological problems such as obsessive compulsive disorder,
aggression and irritability. These individuals are eight times more likely
to commit suicide than members of the general population (Haskins et
al 2000). Walker (2007) and Pulsen et al (2013) have reported that
people who have been diagnosed with HD display multiple physical
symptoms such as: dystonia, bradykinesia and involuntary movements.
Chorea is an example of an involuntary movement; it is seen as the
signature symptom of HD. Chisolm et al (2012) stated that people who
have HD encounter various cognitive issues, ranging from loss of short

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term memory to slurred speech. Sleep deprivation is also common in
people with HD (Morton et al 2012). It has been suggested that due to
the nature of the condition, many complex issues may arise that
impacts on the health-related quality of life (HRQoL) of people with HD
and their families (Williams et al 2011).
The way in which HD is treated has not changed in the last 20 years
according to Walker (2007). Haskins et al (2000) reported that, there
are still no therapies available to alter the progression of the disease or
the disease course. Therefore all current methods of treatment are
focused on managing the symptoms and supportive care (Haskins et al
2000). Thus, well informed decisions are needed to develop suitable
policies that may best alleviate the symptoms of HD in the lives of
those affected by the disease.
Given that resources are limited, every decision made in healthcare
has an opportunity cost, that is an alternative that is forgone (Posnet
1996). In light of this, economist has recommended that economic
evaluations of diseases can serve as a key tool to assist policy makers
to make more justifiable decisions (Drummond et al 2005; Drummond
1996; Drummond 1984 and Rutten 1996) (See Figure 1).There has
been increasing emphasis on economic evaluations across the world in
nations such as the UK, the Netherlands, Canada and Australia (NICE
2004; Commonwealth Department of Health and Ageing 2002; Ministry
of Health 1994 and Rutten 1996).
Drummond et al (1998) states that, many healthcare decision-making
organisations use the findings of cost-utility analysis which is a form of
economic evaluation to aid policy decisions. Torrance (1985) explains
that cost-utility analysis estimates the cost-per-QALY (quality-adjusted
life-year) of treatments or interventions. According Drummond et al
(1998), QALYs assess quality of life and quantity as a single health
outcome measure. Health state values or health utilities form
preference weights or ‘quality’ weights, and they are combined with
survival estimates to calculate QALYs (Brazier et al 2007). Longworth

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(2014) and Brazier et al (2007) reported that generic preference-based
measures such as the EQ-5D, HUI and SF-6D, are commonly used in
economic evaluations because they enable comparison between
different interventions and different groups of people. However, Brazier
et al (2007) also mentions that generic measures may fail to truly
capture how certain diseases can affect an individual’s HRQoL.
Condition specific preference-based measures reflect the impact that a
particular disease has on an individual’s HRQoL; however, it is more
difficult to compare across different conditions and interventions with
these measures (Brazier et al 2007 and Longworth et al 2014).
Health state values or QALY weights for HD health states derived from
good quality research are needed to inform decision-making regarding
interventions for this largely neglected condition (Figure 1). Therefore, a
systematic review was conducted of health state values for HD health
states.
Figure 1: The role of research in providing health state values for HD
have in decision making
The aims for this systematic review were as follows:
 To identify health state values for HD in the published literature;
 To describe these health state values that have been published
for HD health states;

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 To summarise the methods that have been used in published
papers which estimated health state values of health states of
people with HD;
 To comment on the methodological quality of the methods used
to estimate the health state values of health states of people with
HD;
 To assess the content validity of the EQ-5D as a measure of
health-related quality of life for people with HD.
Methods
The methods and reporting framework used for this systematic review
followed the PRISMA (Preferred Reporting Items for Systematic
Reviews and Meta-analyses) guidance which has been adapted for a
methodological systematic reviews of health state values by Liberti et al
(2009).
Initially all of the original reports and published reports were identified,
these included, Health Technology Assessments and reports from
research institutions of empirically-derived health state values for any
HD health state.
Information sources
The following databases were searched on the 6/3/14: Medline in
process (Ovid); Embase (Ovid); PsycINFO (Ovid); Cochrane Library (all
databases); CINAHL (Ebsco) and EconLIT (Ebsco). In addition, the
references of all full text papers that were obtained were screened for
potential eligibility.

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Search strategy
The search strategy comprised two elements used in combination:
i) terms to identify papers relating to HD;
ii) terms to identify reports of health state values.
The HD search terms were devised in collaboration with a librarian at
the University of Exeter Medical School. The health state values search
terms were drawn from previous systematic reviews of health state
values and updated to include more recent methods of health state
valuation, for example, stated preference and discrete choice
experiments. These terms were drawn from different studies, Main et al
(2008); Thompson-Coon et al (2010); Shearer et al (2012) and Ryan
and Gerard (2003). The search terms were significantly adapted to be
appropriate to the particular database, and non-English papers, letters,
editorials and comments were specifically filtered out at this stage of
the review. The search strategies can be seen in Appendix 1.
Study Selection
The inclusion and the exclusion criteria were as follows:
Inclusion criteria
 Study relates in part/full to adults with HD.
 Health state values for HD health states are given.
 Study presents empirically-derived health state values, given for
the first time. (Systematic reviews which presented new
empirical findings of health state values were eligible for
inclusion).
 Published in English.
Exclusion criteria
 Study does not relate to people with HD.
 Study relates to carers of people with HD only.
 Study relates to children only.

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 Health state values are not given.
 Study only uses or applies health state values that have been
previously reported. (If studies were applications of, or used,
previously published research reporting health state values,
these were excluded).
Screening
Two independent reviewers identified papers for potential inclusion in to
this review by reading titles and abstracts. At this stage, cost-utility
studies of treatments for people with HD were included as they should
provide references to original health state value data. Full text papers
of all potentially eligible studies were obtained in order to verify
inclusion or exclusion, and for subsequent data extraction. The reasons
for papers being excluded were documented.
Data extraction
A data extraction form (Appendix 2) was devised and used to extract
information from each of the included studies. An overview of the
extracted items is given in Table 1.
Table 1: Data items extracted from included studies
Study
details
Demographic and
clinical information
Health state value
data
Year of publication Age Descriptive system
Country Gender Method of health state
valuation
Study design HD stage Mean (sd) health state

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value
Sample size Disease duration Health state values by
disease severity
Description of included studies and findings
The studies were described and summarised according to the
characteristics detailed above.
Methodological quality of studies
The methods used to estimate the health state values of people with
HD in the included papers were assessed using the checklist given in
Appendix 3. This is based on two previously published checklists:
‘Check-list for judging the merits of preference-based measures of
health’ (Brazier 1999) and ‘Critical appraisal of a survey’
(Crombie1996). Two factors influenced this decision. Firstly the two
papers identified used cross-sectional survey methods and secondly
the discussion in the Brazier et al (2007) book which explains, in detail,
how to critically appraise different methods of gathering health state
values. Subsequently, the assessment criteria were divided to
separately assess:
i) the health state descriptive system and
ii) the valuation of health states.
The content validity of the EQ-5D
The HDQoL, according to a study carried out by Hocaoglu et al (2012),
is a recently developed measure designed to assess the HRQoL of
people with HD. In Hocoaoglu et al (2012) study, the HDQol was
developed based on a review of the literature, qualitative research and
face-to-face interviews with 31 people with HD living in the UK. The
interviews were audibly recorded and transcribed. 81 initial items were

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generated which were checked with 281 individuals, who had different
stages of disease severity, across 12 European countries. Participants
were asked how frequently they experienced each item, and the extent
to which each item impacted their HRQoL. This resulted in some items
being eliminated and the remaining items were further examined using
Rasch analys; this is a method used to analyse instruments that
measure an individual’s Quality life (Tennant et al 2004).
Due to the robust methods used in the development of the HDQoL, it
seemed fair to assume that HDQoL when this report was written, was
the best measure to fully capture the HRQoL of people with HD. Due to
this, the content validity of the EQ-5D, one of the most commonly used
generic preference-based measure, of HRQoL for people with HD was
carried out (Longworth et al 2014). The content validity of the EQ-5D
was investigated by comparing the EQ-5D dimensions with the HDQoL
scales. Here, as stated by Brazier et al (2007) content validity refers to
the extent to which the measures comprehensively cover the
dimensions of HRQoL affected by HD. This comparison was
undertaken to determine if there were key differences between the
coverage of measures. If the measures assess similar constructs, this
would be indicative of content validity of the EQ-5D for people with HD.
On the other hand, clear differences in coverage of the measures
would suggest that the EQ-5D lacks content validity for measuring the
HRQoL of people with HD.
Results
Article identification
Table 2 shows a breakdown of the number of articles that were
identified by each of the databases.
Table 2: Summary of results from the systematic search

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Study Selection
Figure 2 shows a flow diagram of the number of studies identified,
screened, eligible and included. The electronic database searches
identified 457 papers as potentially eligible. After duplicates were
removed this resulted in 384 potentially eligible papers. Each of these
studies were screened (based on title and abstract), resulting in the
exclusion of 372 papers. There were 12 titles and abstracts that met
the inclusion criteria. Of these 12, 10 titles and abstracts were
conference proceedings, these were: Clay et al (2011) a; Clay et al
(2011) b; Clay et al (2011) c; Clay et al (2010) d; Dorey et al (2011) a;
Dorey et al (2011) b; Dorey et al (2010) c; Dorey et al (2010) d;
Kehremiri et al (2012) and Urbernati et al (2012). Full text articles were
obtained of the two papers Calvert et al (2012) and Hocauglo et al
(2012).
Database Interface Date Hits
Medline OVID 06/03/2014 261
Embase OVID 06/03/2014 135
PsycINFO OVID 06/03/2014 11
CINAHL EBSCO 06/03/2014 23
EconLit EBSCO 06/03/2014 1
Cochrane Library Wiley 06/03/2014 26
Total hits 457

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Figure 2: Flow chart summarising the systematic search
Description of the studies
The two included papers were published in 2012 and were conducted
in the UK. The purpose of the Calvert et al (2012) study was to
examine the HRQoL of individuals who had different rare long-term
neurological conditions, and HD being one of these conditions. The
second paper, Hocaoglu et al (2012) compared how individuals, who
were at different stages of HD valued their own health state, with how
the carers valued the health states of the HD sufferers.
Demographic and clinical characteristics of study participants
The age of participants with HD in the Calvert et al (2012) paper was
57.1 (15.4) years (mean (standard deviation)), and of these participants
45.1% were male. The mean disease duration was 4.9 years, which
was calculated by subtracting the reported mean age in years from the
reported mean age of diagnosis. The disease severity of the
participants was not documented.

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Participants in the Hocaoglu et al (2012) study had a similar age of
56.42 (12.8) (mean (standard deviation)). 58% of the participants were
female, while 42% were male. The duration of disease was not
reported, however, participants were grouped by their HD stage. There
were seven stages. Participants were assigned to stage one if they
were seen to have slight changes in mood and motor control function.
Participants who were grouped in stage two could no longer work, and
needed help with daily activities. Participants, who were assigned to
stage 3, were described as being no longer able to carry out functions
independently. Participants, who needed assistance at home, were
allocated to stage 4. Stage 5 participants needed nursing care. There
was also a presymptomatic stage, which included participants that were
known to have the HD gene mutation but did not show any symptoms.
Finally, the at-risk group was made up of participants who had a family
member who was diagnosed with HD, but their own genetic status was
unknown.
Methods of included studies
Hocaoglu et al (2012) used a self-report postal method to gather data
via the UK HD Association (HDA). This cross-sectional survey
contained 105 individuals who were diagnosed HD. Participants could
ask for help with filling out the survey if required.
The study by Calvert et al (2012) was also cross-sectional in design.
The survey was completed either online or on paper, and participants
could ask for help to complete the survey. In total, 266 participants
were included in this study, and 53 of these participants were
diagnosed with HD. Participants were recruited via a number of
charities: MNDA, HD Association, MSA Trust, Ataxia UK, PSP Europe,
Polio Survey Network, CMT UK, specialist neurology clinics and via the
UK Clinical Research Networks (Dementias and Neurodegenerative
Disease Research Network and the Primary Care Network).
Researchers did not report the number of individuals that were
recruited from the various charities, and the condition that each

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participant had. Therefore it cannot be assumed that the 53 people with
HD were recruited from the HDA.
Sampling and response rate
The two studies recruited participants solely from charities and
associations. It is therefore unlikely that the samples were
representative of the general UK HD population, creating the potential
for selection bias (Berk 1983). People from associations such as the
HAD, could have been from particular subgroups of the HD population.
Thus they may have had certain characteristics. This could mean that
these individuals may have reported their health status in particular
ways which were not comparable with the rest of the HD population.
Both studies failed to mention the response rate; i.e. how many people
the questionnaire was sent to and how many replied. Therefore, it is
only possible to speculate on the type and size of bias that could have
arisen in the two studies.
Health State Values
Brazier et al (2007) explains that to produce a health state value, a
measure needs a descriptive system to describe health states, and a
valuation system to provide values for individuals’ health states.
Health state descriptive systems
Both studies used the EQ-5D, which was Euro Qol group (1996).
Longworth (2014) reported that the EQ-5D is one of the most
commonly used generic, preference-based measure to assess the
HRQoL of individual; and the EQ-5D is recommended by NICE in the
UK in Health Technology Assessment. This measure has five domains
which are: mobility, self-care, usual activities; pain and discomfort;
anxiety and depression according to Robin et al (2001). Robin et al
(2001) also explains that, the five domains are equally weighted in this
measure.

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Health state valuation
In the Hocaoglu et al (2012) study, health state values were derived
from the general population. Given the range of possible values
described, it is assumed that the UK value set suggested by Dolan
(1997) was used, but this is not stated in the paper. Health state values
were also collected from people with HD themselves using the EQ-5D
VAS (Brazier et al 2007).
The general population UK value set was also used in the Calvert et al
(2012) study. Health state values elicited directly from people with HD
were not collected in this research.
The scale for the EQ-5D starts with 0 which is equivalent to death and
ends with 1 which is equivalent to full health. The VAS scale ranges
from 0 (death) to 100 full health.
Health state values of HD health states
Hocaoglu et al (2012) reported a mean (sd) score of EQ-5D of 0.56
(0.35) for people with HD. They also reported a mean (sd) EQ-5D VAS
score of 58.4. The mean EQ-5D score described by Calvert et al (2012)
was 0.3 (no standard deviation was given). Table 3 provides a
summary of the results.
Table 3: Summary of included studies
Authors Calvert, Pall, Hoppitt,
Eaton, Savil and Sackley
Hocaoglu, Gaffan and Ho
Health State Value
instrument
EQ-5D EQ-5D
Mean Score 0.3 0.56
Standard Deviation Not given 0.35
Mean VAS ScoreNot givenhyyytt Not given 58.4

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Standard Deviation VAS
Score
Not given 23.2
Sample Size 53 105
Disease severity Not given
Mean disease duration 4.9
years
Range from ‘At risk’ to
stage 5 (individual needs
nursing care)
Content Validity
To assess the content validity of the EQ-5D for measuring the
HRQoLof people with HD, a table was created. The dimensions of the
EQ-5D formed the columns and the HQoL scales formed the rows (see
Table 3). Information given in Table 3 was obtained, firstly, by
considering the descriptive systems of the two measures (See
Appendix 4 and Appendix 5), and secondly, by referring to the studies
carried out by Hocoaglu et al (2012) and Robin et al (2002). Where the
measure captured similar aspects of an individual’s HRQoL, the box
was green. For example, the square that represented where the
mobility column intercepted the cognitive row, (a, 1) was green; this is
because, mobility is part dependent on an individual’s cognitive ability.
When the measure did not overlap, the square was red. For example
the square where Physical and Function met with Anxiety and
depression (e, 4) was red; this is because, anxiety and depression
considers a person’s psychological state rather than physical state
Of the possible 30 squares only 9 were green indicating similarity
between the two measures.
Table 3: Content validity of EQ-5D for assessing the HRQoL of HD

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EQ-5D dimensions
HDQoL scales Mobility
(a)
Self-care
(b)
Usual
activities
(c)
Pain/
Discomfort
(d)
Anxiety/
Depression
(e)
Cognitive (1)
Hopes & Worries (2)
Services (3)
Physical and
Functional (4)
Mood state (5)
Self and Vitality (6)
Key
Content areas where the EQ-5D and
the HDQoL overlap
Content areas where the EQ-5D and
HDQoL do not overlapped
Discussion
Summary of findings
A systematic review was conducted to identify health state values for
HD health states. Two papers matched the inclusion and exclusion
criteria. Calvert et al (2012) reported an EQ-5D mean score of 0.3 and
Hocaoglu et al (2012) reported an EQ-5D mean score of 0.56.
Hocaoglu et al (2012) also described an EQ-5D VAS score of 58.4.
Strengths and weaknesses of the systematic review

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Six databases were searched for the systematic review, along with
numerous search terms to ensure the thoroughness of the systematic
search (Appendix 1). The systematic search followed the PRISMA
guidance adapted for methodological reviews outlined by Liberti et al
(2009). However, the fact that the ISI Web of Science was not one of
these databases, which may have limited the search in terms of
obtaining, published grey literature.
One of the strengths of this systematic review is that it was the first
conducted regarding the health state values literature for HD. However,
there is a limited amount of extant literature in this field. 10 conference
titles and abstracts were identified from the systematic search. These
studies were Clay et al (2011) a; Clay et al (2011) b; Clay et al (2011)
c; Clay et al (2010) d; Dorey et al (2011) a; Dorey et al (2011) b; Dorey
et al (2010) c; Dorey et al (2010) d; Kehremiri et al (2012) and
Urbernati et al (2012 ). Full text articles were obtained of the two
papers (Calvert et al 2012 and Hocauglo et al 2012).
Analysis of the included articles
The Calvert et al (2012) paper reported that the mean score for people
with HD was 0.3 (no standard deviation were given). Walker (2007)
shown that HD affects a person’s HRQoL differently depending on
disease severity. However, Calvert et al (2012) failed to describe the
disease severity of their participants. Therefore, it is uncertain what the
mean health state value score represents, as it is not known whether
people within the sample had severe, moderate or mild HD.
In contrast, Hocaoglu et al (2012) did describe the disease severity of
participants in their study. The stages spanned the spectrum of the
disease from ‘At risk’ (people that were related to individuals who were
diagnosed with HD), to stage 5 (people with HD that need nursing
care). Despite the spread of disease severity, the paper only stated one
mean EQ-5D score and one mean EQ-5D VAS score, 0.56 and 58.4.
The standard deviations were 0.35, and 23.2 which re-emphasises the
magnitude of variation in the data. For this reason, the relevance of the

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average was limited. A useful addition to the data described would
have been, mean EQ-5D scores for each disease stage. Nevertheless,
because some of the stages included as few as eight people, such
reporting may have had limited validity.
Reported limitations
The Calvert et al (2012) study did not report the disease severity of
study participants. But, researchers did report that the health state
values are generally, more representative of those with advancing
disease. Authors also suggested that, due to this, people with HD may
have wanted to participate in the study as a result of having a lower
perceived view of their own HRQoL.
Calvert et al (2012) described the selection process used in the study
as non-random. They also stated that it was possible that people with
severe limitations were unable to participate in the study.
Hocaoglu et al (2012) did not describe any limitations in their study.
However, it is plausible that people that had severe limitations were
unable to take part in the study
Content Validity
In Table 3, 30% of the squares were green. These findings, coupled
with the nature of HD as described in the Background, imply that the
EQ-5D may be unable to assess the full impact that HD has on a
person’s HRQoL. Ma et al (2001), and Pulsen (2013) have come to
similar conclusions. This raises concerns about the content validity of
the EQ-5D as a measure of HRQoL for people with HD.
Recommendations to improve the methods used to collect health state
values for HD health states
On the basis of this review, there are a few key recommendations on
how the methods used to collect health state values for people with HD

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can be improved that can be made. It is important to present health
state values for each stage of HD according to the widely used HD
measure for disease severity, the Unified Huntington’s Disease Rating
Scale (UHDRS) which is described by, Phillips et al (2008) and Ho et al
(2009). This is because, the way in which HD affects a person’s
HRQoL when they are at risk of the condition, is significantly different to
how HD would affect a person’s HRQoL when they are at Stage 5 (in
need of a nursing home) of the disease according to Walker (2007). It
is therefore crucial that researchers take this into account when
reporting health state values for people with HD.
Furthermore, larger sample sizes are needed for each stage of the
disease to ensure that the health state values are accurate. Hocoaglu
et al (2012) separated their sample into different stages of HD and
reported a single EQ-5D mean score. The number of participants at
one stage comprised only eight; therefore it would have been
inappropriate to report a mean score for each stage.
Finally, it is recommended that researchers should endeavour to make
their samples as representative as possible and therefore, should not
rely solely on associations and charities recruit participants. In an
attempt to reduce recruitment bias, participants who have been
diagnosed with HD could be recruited via GP surgeries.
Future Research
Other studies use different instruments such as the SF 36, as a
descriptive system for the HRQoL for HD according to Ho et al (2009;
and Ho et al 2004). As previously mentioned, the two studies included
in this systematic review use the EQ-5D to provide health state values
for people living with HD. There are other methods available that would
enable researchers to gather health state values for individuals with
HD, such as the SF-6D (SF-6D converts data from the SF 36 into
health state value). However, to date, research has not been carried

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out using the SF-6D to provide health state values of health states for
individuals living with HD. Once such work has been conducted,
researchers will be able to determine which generic preference-based
measure may best capture the HRQoL of people with HD by comparing
the EQ-5D with the SF-6D.
The two included studies used a cross-sectional method, to gather
health state values of individuals with HD. Longitudinal methods should
be considered to explore how the health state values of health states
experienced by people with HD change over time.
Finally, Carlozzi et al (2013) has recommended that future research
should focus on developing the HDQoL into a condition-specific
preference-based measure, which may lead to more accurate health
state values for people with HD in the future.
If all of these recommendations are followed through, it is hoped that
more accurate measures would be used to collect information about the
health state values of individuals that have HD. This may possibly lead
to more accurate methods of measuring the HRQOL for people living
with HD; thus increasing the likelihood of more precise economic
evaluations for HD interventions, which may aid policy makers,
resulting in better policies for people with HD in the future.
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Appendix 1
Search strategy for Medline
1. Huntington$.ti,ab.
2. (Chorea adj4 progressive).ti,ab.
3. (chorea adj4 hereditary).ti,ab.
4. (chorea adj4 chronic).ti,ab.
5. (Westphal and (variant or dis$)).ti,ab.
6. exp Huntington Disease/
7. 1 or 2 or 3 or 4 or 5 or 6
8. "quality adjusted life".tw.
9. (qaly$ or qald$ or qale$ or qtime$).tw.
10. "disability adjusted life".tw.
11. daly$.tw.
12. "health state valu$".ti,ab.
13. "health status".tw.
14. "health related quality of life".tw.

of 43
15. (sf36 or sf 36 or short form 36 or shortform 36 or sf thirtysix or sf thirty six or
shortform thirtysix or shortform thirty six or short form thirty six or short form thirtysix
or short form thirty six).tw.
16. (sf6 or sf 6 or short form 6 or shortform 6 or sf six or sfsix or shortform six or
short form six).tw.
17. (sf12 or sf 12 or short form 12 or shortform 12 or sf twelve or sftwelve or
shortform twelve or short form twelve).tw.
18. (sf16 or sf 16 or short form 16 or shortform 16 or sf sixteen or sfsixteen or
shortform sixteen or short form sixteen).tw.
19. (sf20 or sf 20 or short form 20 or shortform 20 or sf twenty or sftwenty or
shortform twenty or short form twenty).tw.
20. (euroqol or euro qol or eq5d or eq 5d or eq-5d).tw.
21. (hql or hqol or h qol or hrqol or hr qol).tw.
22. (hye or hyes).tw.
23. "health$ year$ equivalent$".tw.
24. "health utilit$".tw.
25. (hui or hui1 or hui2 or hui3).tw.
26. disutil$.tw.
27. rosser.tw.
28. "quality of wellbeing".tw.
29. "quality of well being".tw.
30. qwb.tw.
31. "willingness to pay".tw.
32. "standard gamble$".tw.
33. "time trade off".tw.
34. "time tradeoff".tw.
35. tto.tw.
36. (index adj2 wellbeing).ti,ab,kw.
37. (index adj2 well being).ti,ab,kw.
38. (quality adj2 well being).ti,ab,kw.
39. (quality adj2 wellbeing).ti,ab,kw.
40. (health adj3 utilit$ ind$).ti,ab,kw.
41. ((multiattribute$ or multi attribute$) adj3 (health ind$ or theor$ or health state$ or
utilit$ or analys$)).ti,ab,kw.
42. "stated preference".ti,ab,kw.
43. "discrete choice".ti,ab,kw.
44. HDQOL.tw.
45. exp Value of Life/

of 43
46. exp Health Status Indicators/
47. exp quality adjusted life year/
48. 8 or 9 or 10 or 11 or 12 or 13 or 14 or 15 or 16 or 17 or 18 or 19 or 20 or 21 or 22
or 23 or 24 or 25 or 26 or 27 or 28 or 29 or 30 or 31 or 32 or 33 or 34 or 35 or 36 or
37 or 38 or 39 or 40 or 41 or 42 or 43 or 44 or 45 or 46 or 47
49. 7 and 48
Search strategy for Psyc Info
2. (Chorea adj4 hereditary).ti,ab.
3. (Chorea adj4 progressive).ti,ab.
4. (Chorea adj4 chronic).ti,ab.
6. exp Huntingtons Disease/
7. 1 or 2 or 3 or 4 or 5 or 6
11. daly$.tw.
13. "health status".tw.
short form six).tw.

of 43
26. disutil$.tw.
27. rosser.tw.
30. qwb.tw.
35. tto.tw.
44. HDQOL.tw.
37 or 38 or 39 or 40 or 41 or 42 or 43 or 44
46. 7 and 45
Search Strategy for Embase
2. (Chronic adj4 Chorea).ti,ab.
3. (hereditary adj4 Chorea).ti,ab.
4. (progressive adj4 Chorea).ti,ab.
6. exp Huntington disease/
7. 1 or 2 or 3 or 4 or 5 or 6

of 43
11. daly$.tw.
13. "health status".ti,ab.
short form six).tw.
26. disutil$.tw.
27. rosser.tw.
30. qwb.tw.
35. tto.tw.

of 43
44. HDQOL.tw.
45. exp quality adjusted life year/
46. exp socioeconomics/
47. exp health status indicator/
49. 7 and 48
Econ Lit
1. TI Huntington* OR AB Huntington*
2. TI (Chorea N4 hereditary) OR AB (Chorea N4 hereditary)
3. TI (Chorea N4 Chronic) OR AB (Chorea N4 chronic)
4. TI (Chorea N4 progressive) OR AB (Chorea N4 progressive)
5. TI (Westphal AND variant) OR AB (Westphal AND variant)
6. TI (Westphal AND dis*) OR AB (Westphal AND dis*)
7. (MH "Huntington's Disease")
8. TI "quality adjusted life" OR AB "quality adjusted life"
9. TI (qaly* or qald* or qale* or qtime*) OR AB (qaly* or qald* or qale* or qtime*)
10.TI "disability adjusted life" OR AB "disability adjusted life"
11.TI daly* OR AB daly*
12.TI "health state valu*" OR AB "health state valu*"
13.TI "health status" OR AB "health status"
14.TI "health related quality of life" OR AB "health related quality of life"
15.TI (sf36 or "sf 36" or "short form 36" or "shortform 36" or "sf thirtysix" or "sf
thirty six" or "shortform thirtysix" or "shortform thirty six" or "short form thirty
six" or "short form thirtysix" or "short form thirty six" or "36-item short*") OR AB
(sf36 or "sf 36" or "short form 36" or "shortform 36" or "sf thirtysix" or "sf thirty
six" or "shortform thirtysix" or "shortform thirty six" or "short form thirty six" or
"short form thirtysix" or "short form thirty six" or "36-item short*")
16.TI ("sf6" or "sf 6" or "short form 6" or "shortform 6" or "sf six" or "sfsix" or
"shortform six" or "short form six" or "6 item short*") OR AB ("sf6" or "sf 6" or
"short form 6" or "shortform 6" or "sf six or sfsix" or "shortform six" or "short
form six" or "6 item short*")
17.TI (sf12 or "sf 12" or "short form 12" or "shortform 12" or "sf twelve or
sftwelve" or "shortform twelve" or "short form twelve" or "12-item short*") OR

of 43
AB (sf12 or "sf 12" or "short form 12" or "shortform 12" or "sf twelve or
sftwelve" or "shortform twelve" or "short form twelve" or "12-item short*")
18.TI (sf16 or "sf 16" or "short form 16" or "shortform 16" or "sf sixteen" or
sfsixteen or "shortform sixteen" or "short form sixteen" or "16-item short*") OR
AB (sf16 or "sf 16" or "short form 16" or "shortform 16" or "sf sixteen" or
sfsixteen or "shortform sixteen" or "short form sixteen" or "16-item short*") -
19.TI (sf20 or "sf 20" or "short form 20" or "shortform 20" or "sf twenty or sftwenty
or "shortform twenty of short form twenty" "20-item short*") OR AB(sf20 or "sf
20" or "short form 20" or "shortform 20" or "sf twenty or sftwenty or "shortform
twenty” or “ short form twenty" "20-item short*")
20.TI (euroqol or "euro qol" or eq5d or "eq 5d" or "eq-5d") OR AB (euroqol or
"euro qol" or eq5d or "eq 5d" or "eq-5d")
21.TI (hql or hqol or "h qol" or hrqol or "hr qol") OR AB (hql or hqol or "h qol" or
hrqol or "hr qol")
22.TI (hye or hyes) OR AB (hye or hyes)
23.TI "health* year* equivalent*" OR AB "health* year* equivalent*"
24.TI (health utilit*) OR AB (health utilit*)
25.TI (hui or hui1 or hui2 or hui3) OR AB (hui or hui1 or hui2 or hui3)
26.TI (disutil*) OR AB (disutil*)
27.TI rosser OR AB rosser
28.TI qwb OR AB qwb
29.TI "willingness to pay" OR AB "willingness to pay"
30.TI "standard gamble*" OR AB "standard gamble*"
31.TI "time trade off" OR AB "time trade off"
32.TI "time tradeoff" OR AB "time tradeoff"
33.TI tto OR AB tto
34.TI (Index N2 "well being") OR AB (Index N2 "well being") OR DE (Index N2
"well being")
35.TI (quality N2 well being)OR AB (quality N2 well being) OR DE (quality N2
well being)
36.TI (index N2 wellbeing) OR AB (index N2 wellbeing) OR DE (index N2
wellbeing)
37.TI (quality N2 wellbeing) OR AB (quality N2 wellbeing) OR DE (quality N2
wellbeing)
38.TI (multiattribute* or multi-attribute*) N5 (“health ind*” or theor* or “health
stat*” or utilit* or analys*) or AB (multiattribute* or multi-attribute*) N5 (“health
ind*” or theor* or “health stat*” or utilit* or analys*)
39.TI (health N3 utilit* ind*) OR AB (health N3 utilit* ind*)
40.TI "stated preference*" OR AB "stated preference*"
41.TI "discrete choice" OR AB "discrete choice"
42.TI HDQol OR AB HDQol
43.ZE "value of life; forgone income")

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CINAHL
1. TI Huntington* OR AB Huntington*
2. TI (Chorea N4 hereditary) OR AB (Chorea N4 hereditary)
3. TI (Chorea N4 Chronic) OR AB (Chorea N4 chronic)
4. TI (Chorea N4 progressive) OR AB (Chorea N4 progressive)
5. TI (Westphal AND variant) OR AB (Westphal AND variant)
6. TI (Westphal AND dis*) OR AB (Westphal AND dis*)
7. (MH "Huntington's Disease")
8. TI "quality adjusted life" OR AB "quality adjusted life"
9. TI (qaly* or qald* or qale* or qtime*) OR AB (qaly* or qald* or qale* or qtime*)
10.TI "disability adjusted life" OR AB "disability adjusted life"
11.TI daly* OR AB daly*
12.TI "health state valu*" OR AB "health state valu*"
13.TI "health status" OR AB "health status"
14.TI "health related quality of life" OR AB "health related quality of life"
15.TI (sf36 or "sf 36" or "short form 36" or "shortform 36" or "sf thirtysix" or "sf
thirty six" or "shortform thirtysix" or "shortform thirty six" or "short form thirty
six" or "short form thirtysix" or "short form thirty six" or "36-item short*") OR AB
(sf36 or "sf 36" or "short form 36" or "shortform 36" or "sf thirtysix" or "sf thirty
six" or "shortform thirtysix" or "shortform thirty six" or "short form thirty six" or
"short form thirtysix" or "short form thirty six" or "36-item short*")
16.TI ("sf6" or "sf 6" or "short form 6" or "shortform 6" or "sf six" or "sfsix" or
"shortform six" or "short form six" or "6 item short*") OR AB ("sf6" or "sf 6" or
"short form 6" or "shortform 6" or "sf six or sfsix" or "shortform six" or "short
form six" or "6 item short*")
17.TI (sf12 or "sf 12" or "short form 12" or "shortform 12" or "sf twelve or
sftwelve" or "shortform twelve" or "short form twelve" or "12-item short*") OR
AB (sf12 or "sf 12" or "short form 12" or "shortform 12" or "sf twelve or
sftwelve" or "shortform twelve" or "short form twelve" or "12-item short*")
18.TI (sf16 or "sf 16" or "short form 16" or "shortform 16" or "sf sixteen" or
sfsixteen or "shortform sixteen" or "short form sixteen" or "16-item short*") OR
AB (sf16 or "sf 16" or "short form 16" or "shortform 16" or "sf sixteen" or
sfsixteen or "shortform sixteen" or "short form sixteen" or "16-item short*") -
19.TI (sf20 or "sf 20" or "short form 20" or "shortform 20" or "sf twenty or sftwenty
or "shortform twenty of short form twenty" "20-item short*") OR AB(sf20 or "sf
20" or "short form 20" or "shortform 20" or "sf twenty or sftwenty or "shortform
twenty” or “ short form twenty" "20-item short*")
20.TI (euroqol or "euro qol" or eq5d or "eq 5d" or "eq-5d") OR AB (euroqol or
"euro qol" or eq5d or "eq 5d" or "eq-5d")
21.TI (hql or hqol or "h qol" or hrqol or "hr qol") OR AB (hql or hqol or "h qol" or
hrqol or "hr qol")
22.TI (hye or hyes) OR AB (hye or hyes)
23.TI "health* year* equivalent*" OR AB "health* year* equivalent*"

of 43
24.TI (health utilit*) OR AB (health utilit*)
25.TI (hui or hui1 or hui2 or hui3) OR AB (hui or hui1 or hui2 or hui3)
26.TI (disutil*) OR AB (disutil*)
27.TI rosser OR AB rosser
28.TI qwb OR AB qwb
29.TI "willingness to pay" OR AB "willingness to pay"
30.TI "standard gamble*" OR AB "standard gamble*"
31.TI "time trade off" OR AB "time trade off"
32.TI "time tradeoff" OR AB "time tradeoff"
33.TI tto OR AB tto
34.TI (Index N2 "well being") OR AB (Index N2 "well being") OR DE (Index N2
"well being")
35.TI (quality N2 well being)OR AB (quality N2 well being) OR DE (quality N2
well being)
36.TI (index N2 wellbeing) OR AB (index N2 wellbeing) OR DE (index N2
wellbeing)
37.TI (quality N2 wellbeing) OR AB (quality N2 wellbeing) OR DE (quality N2
wellbeing)
38.TI (multiattribute* or multi-attribute*) N5 (“health ind*” or theor* or “health
stat*” or utilit* or analys*) or AB (multiattribute* or multi-attribute*) N5 (“health
ind*” or theor* or “health stat*” or utilit* or analys*)
39.TI (health N3 utilit* ind*) OR AB (health N3 utilit* ind*)
40.TI "stated preference*" OR AB "stated preference*"
41.TI "discrete choice" OR AB "discrete choice"
42.TI HDQol OR AB HDQol
43.(MH "Economic Value of Life")
44.(MH "Quality-Adjusted Life Years")
45.(MH "Health Status Indicators")
Search strategy for Cochrane
1. Huntington*:ti,ab
2. (chorea near/4 Chronic):ti,ab
3. (Chorea near/4 Progressive):ti,ab
4. (hereditary near/4 Chorea):ti,ab
5. Westphal and dis*:ti,ab
6. Westphal and variant:ti,ab
7. MeSH descriptor: [Huntington Disease] explode all trees
8. #1 or #2 or #3 or #4 or #5 or #6 or #7
9. "quality adjusted life":ti,ab
10.(qaly* or qald* or qale* or qtime*):ti,ab

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11."disability adjusted life":ti,ab
12.daly*:ti,ab
13."health state valu*":ti,ab
14."health status":ti,ab
15."health related quality of life":ti,ab
16.(sf36 or sf 36 or shortform 36 or sf thirtysix or sf thirty six or shortfom thirtysix
or shortform thirty six or short form thirty six or short form thirtysix or short
form thirty six):ti,ab
17.(sf6 or sf 6 or short form 6 or shortform or sf six or sfsix or shortform six or
short form six):ti,ab
18.(sf16 or sf 16 or short form 16 or shortform 16 or sf sixteen or sfsixteen or
shortfom sixteen or short form sixteen):ti,ab
19.(sf 12 or sf 12 or short form 12 or shortform 12 or sf twelve or sftwelve or
shortform twelve or short form twelve):ti,ab
20.(sf20 or sf 20 or short form 20 or shortform 20 of sf twenty of shorfform
twenrty or short form twenty):ti,ab
21.(euroqol or euro qol or eq5d or eq 5d or eq-5d):ti,ab
22.(hql or hqol or h qol or hrqol or hr qol):ti,ab
23.(hye or hyes):ti,ab
24."health* year* equivalent*":ti,ab
25."health utilit*":ti,ab
26.(hui or hui1 9or hui2 or hui 3):ti,ab
27.dusutil*":ti,ab
28."rosser":ti,ab
29."quality of wellbeing":ti,ab
30."qualtiy of well being":ti,ab
31.qwb:ti,ab
32."willingness to pay":ti,ab
33."standard gamble*":ti,ab
34."time trade off":ti,ab
35."time tradeoff":ti,ab
36."tto":ti,ab
37."index Near/2 well being":ti,ab,kw
38."quality NEAR/2 well being":ti,ab,kw
39."quality NEAR/2 wellbeing":ti,ab,kw
40.((multiattribute* or multiattribute*) near/3 (health ind* or theor* or health state*
or utilit* or analys*)):ti,ab
41."stated preference":ti,ab

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42."discrete choice":ti,ab
43.HDQOL:ti,ab
44.MeSH descriptor: [Value of Life] explode all trees
45.MeSH descriptor: [Health Status Indicators] explode all trees
46.MeSH descriptor: [Quality-Adjusted Life Years] explode all trees
47.9 or10 or 11 or 12 or 13 or 14 or 15 or 16 or 17 or 18 or 19 or 20 or 21 or 23
or 24 or 25 or 26 or 27 or 28 or 29 or 30 or 31 or 32 or 33 or 34 or 35 or 36 or
48.49 8 and 48
Appendix 2
Data Extraction form
Data Comments
Study details
Authors
Year
Country
Study design
Sample size
Demographic and clinical
information
Age
Gender
Disease type
Disease duration
HD stage
Health state values
Measure used

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Health state values (mean,
standard deviation, range, median,
inter-quartile range)
Health state values by HD stage
Appendix 3
Details
The descriptive system
1. Was a generic or condition-specific descriptive system used?
2. Was a standardised questionnaire used? y / n
3. If yes, which questionnaire was used?
4. If no, what descriptive system was used?
5. Was the questionnaire or descriptive system that was used
appropriate for use in HD in terms of:
y / n
a. Face validity: Were the items relevant and appropriate to MS? y / n
b. Content validity: Were all dimensions of health of interest
included?
y / n
6. Could the sampling method for those who completed the
descriptive system have introduced selection bias (i.e. the sample
was unlikely to have been representative)?
y / n

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7. Was the response rate achieved likely to have introduced
significant bias (e.g. a response rate of less than 50%)?
y / n
The health state valuation process
8. Were health state values from the general population used? y / n
9. If yes, which dataset/algorithm was used?
10. Were health state values from people with HD used? y / n
11. If yes:
a. What method of valuation was used?
e.g. standard gamble, time trade-off, VAS?

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Appendix 4
HDQOL
Cognitive Hopes
and
Worries
Services Physical and
Functional
Mood
States
Self and
vitality
Everyday
memory
HD Family
Worry
Management
of HD
Hobby Sleep HD family
worry
Organise day HD worry Services on
HD
Weight Irritated Support
Remember
Date
Hope Information
on HD
Eating Temper Socialise
Concentration Financial
Concerns
Dressing Low mood Role in
family
Multitask Other’s
attitude to
HD
Walking Socialised Motivation
Slow Operate
television
Get on
with life
Tired
Follow
Conversation
Swallowing Motivation
Use Words Carrying
things
Decision
Making
Balance
Personal
wishes
Independence
Jobs around
the house

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Appendix 5
EQ-5D
Mobility
I have no problems in walking about
I have some problems in walking about
I am confined to bed
Self-Care
I have no problems with self-care
I have some problems with washing or dressing myself
I am unable to wash or dress myself
Usual Activities (e.g. work, study, housework, family or leisure activities)
I have no problems with performing my usual activities
I have some problems with performing my usual activities
I am unable to perform my usual activities
Pain / Discomfort
I have no pain or discomfort
I have moderate pain or discomfort
I have extreme pain or discomfort
Anxiety / Depression
I am not anxious or depressed
I am moderately anxious or depressed
I am extremely anxious or depressed

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