This document summarizes a systematic review that examined and compared the content of health-related quality of life (HRQoL) measures used for stroke patients based on the International Classification of Functioning, Disability and Health (ICF). The review identified 13 HRQoL measures (6 generic and 7 stroke-specific) frequently used with stroke patients. Researchers linked 979 concepts from the measures to 200 different ICF categories. While no category was common to all measures, the category for "emotional functions" was most frequent. Stroke-specific measures addressed "mental functions" more while generic measures included "environmental factors" more. The study provides an overview of content coverage of current HRQoL measures for stroke to help clinicians and

1. Content comparison of health-related quality of life measures
used in stroke based on the international classification
of functioning, disability and health (ICF): a systematic review
S. Geyh Æ A. Cieza Æ B. Kollerits Æ G. Grimby Æ
G. Stucki
Received: 14 June 2006 / Accepted: 3 January 2007 / Published online: 10 February 2007
Ó Springer Science+Business Media B.V. 2007
Abstract
Objective To examine and compare the contents of
health-related quality of life (HRQoL) measures used
in stroke, based on the ICF as the frame of reference.
Design We conducted a systematic literature review
to select current generic and condition-specific
HRQoL measures applied in stroke. We examined the
contents of the selected measures by linking the con-
cepts within the instruments’ items to the ICF.
Results The systematic literature review resulted in
the selection of six generic and seven stroke-specific
HRQoL measures. Within the selected instruments we
identified 979 concepts. To map these concepts, we
used 200 different ICF categories. None of the ICF
categories is contained in all of the instruments. The
most frequently used category is ‘b152 Emotional
functions’ contained in 53 items from 10 instruments.
Stroke-specific measures more often address ‘Mental
functions’, while the selected generic instruments more
often include Environmental Factors.
Discussion The present study provides an overview on
current HRQoL measures in stroke with respect to their
covered contents and provides valuable information to
facilitate the selection of appropriate instruments for
specific purposes in clinical as well as research settings.
Keywords Cerebrovascular disorders Á Stroke Á
Outcome assessment Á Health status Á
Quality of life Á ICF
Introduction
Health-status measures are applied for a great variety
of purposes in clinical, research, management, and
policy settings [58]. Following stroke, health-status
measures might be used for the examination and
description of stroke impact, for monitoring, inter-
vention evaluation, quality management, surveys, for
individual as well as macro-level health-care planning
and decision making.
Most frequently, the effects of stroke are assessed by
methods, such as health professional ratings and per-
formance tests [27, 41, 55, 66], e.g. the Barthel Index
[57], the National Institutes of Health Stroke Scale [9],
the Rankin Scale [63], or the Mini-Mental State
Examination [38]. However, stroke survivors’ everyday
lives are affected in a variety of ways not easily cap-
tured by this type of method [62].
Health-related quality of life (HRQoL) measures
provide a comprehensive patient-centered approach to
specify consequences of stroke. HRQoL measures
contain the individual patients’ report on the impact of
a disease and its treatment on different domains of
their daily life and health experience [1, 8, 59, 92].
S. Geyh Á A. Cieza Á B. Kollerits
ICF Research Branch of the WHO FIC Collaborating
Center (DIMDI), IHRS, Ludwig-Maximilians-University,
Munich, Germany
G. Grimby
Department of Rehabilitation Medicine, Sahlgrenska
University Hospital, Goteborg, Sweden
G. Stucki (&)
Department of Physical Medicine and Rehabilitation,
Ludwig-Maximilians-University, Marchioninistr. 15, 81377
Munich, Germany
e-mail: gerold.stucki@med.uni-muenchen.de
G. Stucki
Swiss Paraplegic Research (SPF), Nottwil, Switzerland
123
Qual Life Res (2007) 16:833–851
DOI 10.1007/s11136-007-9174-8

2. The increasing use of HRQoL measures reflects the
awareness that the patients’ perspective is at the core
of health-care provision and research. Assessing
HRQoL extends outcome measurement, based on
performance and adds relevant information for treat-
ment decision-making, efficacy evaluation and the
interpretation of outcomes [1, 48].
HRQoL measures are established in several dis-
eases, such as cancer, musculoskeletal, or cardiovas-
cular conditions [39, 71]. However, in stroke a
reluctance to endorse this type of instrument is
apparent [27, 66]. The use of self or interviewer-
administered questionnaires is often difficult in stroke
patients, due to the deficits imposed by stroke itself,
especially communication and cognitive impairments.
Generic measures provide major advantages, espe-
cially for the comparison of different health conditions.
However, available generic measures face the funda-
mental criticism that they fail to cover relevant stroke-
related problems, for example cognitive and language
difficulties [23, 42]. Also, as they might suffer from
floor and ceiling effects and might be unresponsive to
change, they cannot represent the diversity in stroke
severity or the dynamic process of recovery [10, 42, 90].
To meet these challenges recently new stroke-specific
HRQoL measures are increasingly being developed.
Different HRQoL measures may fit different pur-
poses. Thus, the selection of an appropriate instrument
for a particular objective is essential in planning any
data collection. A thorough examination and evalua-
tion of measures along various criteria is necessary to
fulfill this goal [37, 73]. The psychometric properties
(e.g. reliability, validity, etc.) and the application-re-
lated features (e.g. administration mode, burden, etc.)
of the instruments need to be accounted for. However,
the first and most important concern is face and con-
tent validity [58].
Therefore, it is of particular interest to examine the
contents of HRQoL measures and to compare the
concepts covered for a well-founded choice of instru-
ments. To facilitate the selection of appropriate
instruments applied in stroke, several reviews can be
relied upon, which mainly describe the measures’
psychometric properties [8, 10, 18, 42, 86]. However,
content comparisons are seldom represented in the
literature. The attempts performed so far [42] used
domains that have not been explicitly defined, were not
comprehensive, and have only been derived for the
limited scope of a single review. Thus, a content
comparison based on a universally accepted,
well-defined, and standardized reference system, that
allows for a detailed exploration and comparison of all
contents of the measures would be valuable.
The World Health Organization’s (WHO) Interna-
tional Classification of Functioning, Disability and
Health (ICF) [94] is a multipurpose classification
developed to provide a common language for the
description of a wide range of health-related phenom-
ena. The ICF is a proven useful tool for the examination
and comparison of HRQoL measures [14, 68, 69, 70],
and can be applied in stroke for several reasons.
The ICF is based on a widely accepted framework
[28], namely the biopsychosocial model of functioning,
disability and health. Several authors have dealt with the
conceptual connections between HRQoL and the ICF
[32, 54, 61, 92]. In stroke rehabilitation and outcome
measurement the ICF currently gains in importance [3,
5, 64, 68, 69, 70, 86]. However, the ICF consists not only
of the conceptual framework, but also of a detailed,
universal, and etiologically neutral classification.
Using the ICF as an independent and external ref-
erence to represent the contents of measures, it is
possible to explore these contents in a comprehensive,
standardized and transparent way. Thereby, the choice
of assessment instruments can be facilitated in all fields
of application [11, 13].
Therefore, the aim of our study is to examine and
compare the contents of HRQoL measures used in
stroke, based on the ICF as the frame of reference. The
specific aims are: (1) to identify current generic and
condition-specific HRQoL measures applied in stroke
patients, (2) to examine the contents of the measures
based on their linkage to the ICF, and (3) to compare
the contents of the generic and stroke-specific HRQoL
measures.
Methods
We conducted a systematic literature review to identify
and select current generic and condition-specific
HRQoL measures applied in stroke. We examined
the contents of the selected measures by extracting the
meaningful concepts contained in the items of the
measures and linking them to the ICF using established
linking rules [11, 13]. The frequencies of ICF categories
representing the concepts contained in the instruments
built the basis of the descriptive analysis and content
comparison.
Identification of HRQoL measures
We searched the electronic databases MEDLINE,
EMBASE and PsycINFO using the keywords ‘cere-
brovascular accident’ or ‘stroke’, and ‘health status’ or
‘quality of life’. The exact search terms varied per
834 Qual Life Res (2007) 16:833–851
123

3. database, as we used the specific thesaurus vocabulary
of the given database. We limited the searches to ori-
ginal articles published between 1999 and 2004 in the
English language, but did not impose restrictions
regarding study design at this point.
The eligibility checks comprised three steps. In a
first step, we used the information of the main abstract
to include descriptive, evaluative (e.g. randomized
controlled trials, clinical controlled trials, etc.) as well
as psychometric studies. The studies should present
firsthand data concerning patients with ischemic or
hemorrhagic stroke. We included studies irrespective
of the type of intervention, setting, or phase of stroke
care. We excluded reviews, case reports, economic
evaluations and primary prevention studies, as well as
studies including non-stroke or healthy persons. In a
second step, we selected studies that reported the use
of HRQoL measures. Finally, we retrieved the full text
articles of the selected studies and checked them again
using the same eligibility criteria. We documented all
HRQoL measures used in the included studies.
To select HRQoL measures for content examina-
tion, we relied on the number of included studies,
which report on the application of these instruments.
We assumed that measures frequently applied in dif-
ferent fields of stroke research have certain relevance
in the field. For practicability reasons we set an a-priori
cut-point for the selection of HRQoL measures. We
selected the five most frequent generic and the five
most frequent stroke-specific instruments for content
examination and comparison.
ICF-based content examination
The ICF
We used the ICF as a tool for the examination of the
HRQoL measures’ content. The ICF is made up of
three components that address functioning and dis-
ability, namely Body Functions, Body Structures, and
Activity and Participation. In addition, the ICF con-
tains Environmental Factors as a fourth component,
describing contextual factors, which might influence
functioning and disability.
The units of the ICF classification are called cate-
gories; they are organized within a hierarchically nes-
ted structure and are denoted by unique alphanumeric
codes. Within each of the four major components
(Body Functions, Body Structures, Activity and Par-
ticipation, Environmental Factors), the categories are
arranged in a stem/branch/leaf scheme. Each compo-
nent consists of chapters (categories at the first level),
each chapter consists of second level categories, and in
turn they are made up of categories at the third level,
and so on. Figure 1 illustrates the structure of the ICF.
An example from the component Body Functions is
presented in the following:
‘b1 Mental functions’(first/ chapter level)
‘b114 Orientation functions’(second level)
‘b1142 Orientation to person’(third level)
‘b11420 Orientation to self’(fourth level).
Linkage procedure
The linkage procedure starts with the identification of
the meaningful concepts contained within the items of
the measures. In the next step, the linkers translate the
meaningful concepts into corresponding ICF catego-
ries, which most precisely represent the concepts.
Utilizing a modified version of established linking
rules [11, 13], the selected measures were linked to the
ICF by two psychologists experienced in the linkage
procedure (BK, EA). The linkage rules are guidelines,
ICF
Body Functions Body Structures Activity and Participation Environmental Factors
1st level
2nd level
3rd level
4th level
8 Chapters
114
323
48
8 Chapters
56
158
88
9 Chapters
118
266
5 Chapters
74
179
Fig. 1 The structure of the
ICF and the distribution of
the ICF’s 1454 categories
across its four components
and four levels of hierarchy
Qual Life Res (2007) 16:833–851 835
123

4. which enable concepts contained in health-status mea-
sures to be linked to the ICF in a standardized manner.
For example, the item of the Burden of Stroke Scale
[23, 25] ‘‘Because of your stroke, how difficult is it for
you to kneel down or bend over?’’ has been linked to the
ICF categories ‘d4102 Kneeling’ and ‘d4105 Bending’.
Concepts that cannot be linked to the ICF are
documented in two ways. If it is not possible to specify
sufficiently which ICF category to use, the concept is
coded ‘not definable’. For example, concepts such as
‘physical disability’, or ‘health’ are not precise enough
to be linked. If a concept is not represented by the ICF,
this concept is labelled ‘not covered’. Such concepts
may be related for example to Personal Factors, for
which no categories currently exist, although they are
considered a part of the contextual factors within the
ICF’s biopsychosocial model. Also, ‘not covered’ may
represent concepts that lay outside the scope of the
ICF, e.g. disease conditions or diagnoses.
Both linkers conducted the linkage procedure inde-
pendently from each other, thus two independent link-
age versions of each instrument were created, then
compared. To resolve disagreements concerning the
selected categories, a third person trained in the linking
rules was consulted (AC or SG). In a discussion led by
the third person, the two health professionals who linked
the instruments stated their pros and cons for the linking
of the concept to an ICF category. Based on these
statements, the third person made an informed decision.
To evaluate the reliability of the linkage process, we
calculated kappa coefficients [16] and nonparametric
bootstrapped confidence intervals [35, 84] based on the
two independent linkage versions of each instrument.
We calculated kappa statistics per component at the
1st, 2nd, and 3rd ICF levels to indicate the degree of
agreement between the two linkers. We performed the
kappa analysis using SAS [72].
The agreed version of the linkage of each instrument
served as the basis for the quantitative descriptive
analysis and content comparison of the measures.
Meaningful concepts
To describe the results of the linkage procedure, first,
we summarize the number of meaningful concepts
which the linkers identified in the selected instruments.
Thereby, we distinguish between the number of con-
cepts that the linkers coded using the ICF and the
number of concepts which the linkers denoted as ‘not
covered’ or ‘not definable’. In addition, we consider the
frequency distribution of the linked meaningful
concepts across ICF components and across the ICF’s
levels of hierarchy.
For each instrument, we use the ratio of the number
of concepts divided by the number of the instruments’
items to characterize the measures’ content density.
Hereby, a value of 1 means that each item of the
instrument contains one concept. The higher the value,
the more concepts are contained within one item of the
measure on average, and the higher the measures’
content density.
Representation of the meaningful concepts by ICF
categories
Further on, we summarize the number of different ICF
categories, which the linkers used to represent the
meaningful concepts of the selected HRQoL measures.
We indicated the measures’ bandwidth of content
coverage by analyzing the frequency distribution of the
ICF categories across the four components of the ICF,
as well as calculating the percentage of the total of
existing ICF categories covered by the HRQoL mea-
sures. Bandwidth refers to the breadth of the health-
related aspects measured.
We characterize the content diversity of an instru-
ment by using the ratio of the number of different ICF
categories applied during the linkage divided by the
number of meaningful concepts. A value of 1 indicates
that each meaningful concept of the instrument cor-
responds to a different ICF category. A value towards
zero indicates lower content diversity, i.e. that several
concepts of the instrument correspond to one and the
same ICF category.
Finally, we examine the frequency of each ICF
category within the selected instruments.
Comparison of generic and stroke-specific HRQoL
measures
To compare generic and stroke-specific HRQoL mea-
sures, we summarize the instruments’ content density,
bandwidth of content coverage, and content diversity
for the two types of measures. In addition, we explore
the frequency of the ICF categories addressed in the
generic and the stroke-specific measures.
Results
Identification of HRQoL measures
The electronic literature searches in MEDLINE, EM-
BASE and PsycINFO conducted in May 2004 yielded
1727 hits. After the three steps of the eligibility checks,
836 Qual Life Res (2007) 16:833–851
123

5. we included 71 studies. In these studies 23 different
HRQoL measures were used. Table 1 shows the full
names and acronyms of all identified HRQoL mea-
sures, as well as the number of included studies which
reported their use.
For the ICF-based content examination we selected
six generic [4, 47, 52, 79, 88, 93] and seven stroke-
specific instruments [23, 25, 30, 31, 36, 45, 49, 83, 91]
according to their frequency. The number of selected
measures exceeds the preset cut-point of five generic
and five stroke-specific measures, because some mea-
sures had equal frequencies. Table 2 provides an
overview on the major characteristics of the selected
HRQoL measures.
ICF-based content examination
Reliability of the linkage procedure
The linkers identified 979 meaningful concepts within
the 13 selected HRQoL measures. In 82% (n = 798) of
the concepts the two linkers agreed upon which ICF
category to assign. For 18% (n = 181) of the concepts,
a structured discussion with a third expert took place to
decide on which ICF category to choose. Table 3 shows
the results of the evaluation of the linkage procedure
by kappa statistics and bootstrapped confidence inter-
vals. Estimated kappa values range from 0.46 to 0.84.
None of the 95% confidence intervals encloses zero,
thus linker agreement exceeds chance.
Meaningful concepts
Figure 2 gives an overview of the number of the
identified meaningful concepts and their distribution
across the major components of the ICF. Out of the
total 979 concepts, we linked 866 (88%) to the ICF.
Most concepts addressed contents from the component
Activity and Participation (n = 586, 60%). In contrast,
we linked 5% (n = 47) of the concepts to Environ-
mental Factors. No instrument contained concepts
referring to Body Structures. Regarding the ICF’s
levels of hierarchy, we assigned most concepts to ICF
categories at the 2nd and 3rd levels (n = 429, 44% and
n = 385, 39%). We coded 113 concepts (12%) as ‘not
definable’ (n = 55, 6%) or ‘not covered’ (n = 58, 6%).
Table 4 shows the number of identified meaningful
concepts for each of the selected instruments. It also
shows the number of concepts linked to the ICF and
the number of concepts which we denoted ‘not defin-
able’ or ‘not covered’, as well as the content density of
each HRQoL measure.
The SIP contains the highest (n = 213) and the EQ-
5D the lowest number of concepts (n = 14).
The QLI-SV contains the highest number of con-
cepts classified as ‘not covered’ (n = 20 out of 76,
26%). The QLI-SV includes several items on overall
satisfaction, for example, the item ‘‘How satisfied are
you with your life in general?’’. Within these items the
concept ‘‘satisfaction’’ is not covered by the ICF but
represents a ‘Personal Factor’.
The HSQuale contains the highest number of con-
cepts that were coded ‘not definable’ (n = 14 out of 123,
11%). For each of its subscales this instrument includes
one overall question about the changes of quality of life.
For example, ‘‘Would you say changes you have noticed
in your physical functioning that have resulted from your
bleed have increased, decreased, or not changed the
quality of your life?‘‘ Within these items the concept
‘‘quality of life’’ cannot be mapped to one definite ICF
category and is coded ‘not definable’.
The content density ratio of the measures shows the
highest value for the LHS (9.2), which has 6 items
containing 55 concepts. It is lowest for the QLI-SV
(1.1), which has 72 items containing 76 concepts.
Representation of the meaningful concepts by ICF
categories
Table 4 shows the number of different ICF categories
employed to represent the instruments’ concepts for
each HRQoL measure. The table also shows the cat-
egories’ frequency distribution across the ICF compo-
nents and the ICF levels of hierarchy.
To map the meaningful concepts of the 13 instru-
ments, we used a total of 200 different ICF categories
corresponding to 14% of all existing ICF categories.
We selected 126 different categories from the com-
ponent Activity and Participation, which cover 32% of
all existing ICF categories of this component. In con-
trast, we applied 19 different categories from the
component Environmental Factors covering 7% of all
existing categories of this component.
No instrument contains concepts referring to Body
Structures. Out of the 13 HRQoL measures seven in-
clude concepts which we linked to Body Functions and
Activity and Participation. Additionally, five instru-
ments also addressed Environmental Factors. Only one
of the selected measures, namely the RNL, does not
cover Body Functions.
The instrument with the broadest bandwidth of
content coverage is the SIP, which was linked to 104
different ICF categories. The SIP covers 5% of all
existing Body Functions, 17% of all categories in the
Qual Life Res (2007) 16:833–851 837
123

6. Table1Frequencyoftheuseofthe23differentHRQoLmeasuresinthe71includedstudieslistedfordifferentstudytypes
InstrumentsRank
order
Frequencyinallstudy
types,n=71(%)*
Descriptivestudies,
n=42
Intervention
evaluation,n=11
Psychometric
studies,n=18
Genericinstruments
SF-36MedicalOutcomesStudy36-Item
Short-FormHealthSurvey
131(44)2038
RNLReintegrationtoNormalLivingIndex29(13)621
SIPSicknessImpactProfile29(13)711
EQ-5DEuropeanQualityofLifeInstrument37(10)412
LHSLondonHandicapScale45(7)212
NHPNottinghamHealthProfile54(6)13
COOPDartmouthCOOPCharts62(3)11
15-D15-DimensionalMeasureofHealth
RelatedQualityofLifeTest
71(1)11
LIFE-HAssessmentofLifeHabits71(1)1
AQoLAssessmentofQualityofLife71(1)1
CHARTCraigHandicapAssessmentand
ReportingTechnique
71(1)1
HUIIIHealthUtilitiesIndexMarkII71(1)1
HSQHealthStatusQuestionnaire71(1)1
LQLPLancashireQualityofLifeProfile71(1)1
QLIQualityofLifeIndex71(1)1
WHOQOLWorldHealthOrganizationQualityof
LifeScale
71(1)1
Stroke-specificinstruments
SISStrokeImpactScale15(7)14
SSQOLStroke-SpecificQualityofLifeScale24(6)22
SAQOL-39StrokeandAphasiaQualityofLife
Scale
32(3)11
QLI-SVQualityofLifeIndex-StrokeVersion32(3)2
SA-SIP30Stroke-AdaptedSicknessImpact
Profile-30
32(3)11
BOSSBurdenofStrokeScale41(1)1
HSQualeQualityofLifeInstrumentforYoung
HemorrhagicStrokePatients
51(1)1
Blankspacesmeannoentryinthisfield
*Percentagesdonotsumupto100,asinseveralstudiesmorethanoneinstrumentwasapplied
838 Qual Life Res (2007) 16:833–851
123

7. Table2OverviewonthemajorcharacteristicsoftheselectedHRQoLmeasures
InstrumentDimensions/
subscales
ModeofadministrationNumber
ofitems
andresponse
options
TimeframeTimeto
complete
Reliability
and
validity
instroke
examined
VersionsReferences
SF-36MedicalOutcome
StudyShort-
Form-36Health
Survey
Physicalfunctioning,
mentalhealth,social
functioning,role
limitationsphysical,
rolelimitations
emotional,general
healthperceptions,
vitality,bodilypain
Self,Interviewer,
Proxy,Telephone
36items,yes/
no,3to6
pointscales
Present,
Past4
weeks
~10minyes[2,22,44,51,
88]
RNLReintegrationto
NormalLiving
Index
Dailyfunctioning,
perceptionofself
Self,Interviewer,Proxy11items,VASPresent~10minyes[15,17,80,93]
SIPSicknessImpact
Profile
Sleep/rest,eating,work,
homemanagement,
recreation/pastimes,
ambulation,mobility,
bodycareand
movement,social
interaction,alertness
behaviour,emotional
behaviour,
communication
Self,Interviewer136items,
yes/no
Today~20–30minyesAstroke
specific
version
exists:the
SA-SIP30
[4,19,75,83]
EQ-5DEuropeanQuality
ofLife
Instrument
Mobility,self-care,usual
activities,pain/
discomfort,anxiety/
depression
Self,Interviewer,Proxy5items,3
ordered
response
options,100
pointVAS
Today
compared
withpast
12months
~5minyes[20,21,22,60,
79]
LHSLondonHandicap
Scale
Mobility,physical
independence,
occupation,social
integration,
orientation,economic
self-sufficiency
Self,Interviewer6items,6
ordered
response
options
Lastweeknotreportedyes[46,47,53]
NHPNottingham
HealthProfile
Physicalabilities,pain,
emotionalreactions,
energylevel,sleep,
socialisolation
Self,Interviewer45items,
yes/no
Present~10–15minyes[33,43,52,85]
SISStrokeImpact
Scale
Strength,memory/
thinking,emotion,
communication,ADL/
IADL,mobility,hand
function,participation
Self,Interviewer,Proxy59items,5point
scale
Past1to4
weeks
notreportedyes[26,28,29,30,
31,34]
Qual Life Res (2007) 16:833–851 839
123

8. Table2continued
InstrumentDimensions/
subscales
ModeofadministrationNumber
ofitems
andresponse
options
TimeframeTimeto
complete
Reliability
and
validity
instroke
examined
VersionsReferences
SSQolStroke-Specific
QualityofLife
Scale
Self-care,vision,
language,mobility,
work/productivity,
upperextremity
function,thinking,
personality,mood,
familyroles,social
roles,energy
Interviewer,Proxy62items,
5pointscale
Pastweek~12minyesAmodified
version
for
aphasic
patients
exists:the
SAQoL-
39
[91]
SAQol-
39
Strokeand
Aphasia
QualityofLife
Scale-39
Physical,psychosocial,
communication,energy
Interviewer39items,
5pointscale
PastweeknotreportedyesModified
versionof
theSS-
QoLfor
aphasic
patients
[49,50]
QLI-SVQualityoflife
IndexStroke
Version
Healthandfunctioning,
socio-economic,
psychological-spiritual,
family
Self,Interviewer72items,
6pointscale
Present~10minyesStroke
specific
versionof
theQLI
[36,56,67]
SA-
SIP30
Stroke-Adapted
SicknessImpact
Profile-30
Bodycareand
movement,social
interaction,mobility,
communication,
emotionalbehaviour,
household
management,alertness
behaviour,ambulation
Self,Interviewer30items,yes/noPresentnotreportedyesStroke
specific
versionof
theSIP
[82,83]
BOSSBurdenofStroke
Scale
Mobility,selfcare,
swallowing,energyand
sleep,domainmood,
domainsatisfaction,
domainrestriction,
positivemood,negative
mood,communication,
cognition,social
relations
Interviewer65items,
5pointscale
Present,
Since
stroke
notreportedyes[23,24,25]
HS
Quale
Instrumentfor
Young
Hemorrhagic
StrokePatients
Generaloutlook,physical
functioning,cognitive
functioning,
relationships,social/
leisureactivities,
emotionalwell-being,
work/financialstatus
Interviewer54items,4to7
ordered
response
options,3
open
questions
Implicit
present,
Since
bleed
~15minyes[45]
840 Qual Life Res (2007) 16:833–851
123

9. component Activity and Participation, and 4% of the
Environmental Factors. The instrument with the nar-
rowest bandwidth of content coverage is the EQ-5D.
For the linkage of the concepts of the EQ-5D we
needed 12 different ICF categories covering 3% of all
existing categories from the component Activity and
Participation and < 1% of all Body Functions.
The content diversity ratio is lowest for the QLI-SV
(0.33), where we used 25 different ICF categories to
represent 76 concepts. The content diversity is highest
in the EQ-5D (0.86), where we used 12 different ICF
categories to map 14 concepts.
The ICF categories applied to map the contents of
the instruments most frequently belong to the 3rd level
(n = 109) and the 2nd level (n = 78) of the ICF hier-
archy.
Tables 5 through 7 show the coverage of ICF cate-
gories from the components Body Functions, Activity
and Participation, and Environmental Factors by the
selected measures. The tables display the linkage re-
sults summarized at the 2nd level of the ICF. Tables
with the detailed linkage results at all levels of the
ICF’s hierarchy and including the frequency of the ICF
categories’ use for the linkage of each instrument are
available from the authors.
None of the ICF categories is contained in all
instruments. The most frequently used category is
‘b152 Emotional functions’, which is contained in 53
items from 10 different instruments. In addition, the
SA-SIP30 contains one item, which refers to a related
3rd level category. The ICF categories ‘d540 Dressing’
and ‘d760 Family relationships’ are both represented in
11 of the 13 instruments. Dressing is not contained in
the SIS and the QLI-SV. However, the SIS contains
related categories at the 3rd level. Moreover, all
measures contain at least one of the six different 3rd
level categories belonging to ‘d920 Recreation and
leisure’.
From the total of 200 different categories used, we
applied 77 categories (40%) to only one of the 13
measures, respectively. The remaining 123 categories
(60%) were each applied in more than one of the
measures.
Comparison of generic and stroke-specific HRQoL
measures
Table 8 shows the number of identified meaningful
concepts and the number of different ICF categories
used to represent the measures’ contents summarized
for the generic and the stroke-specific HRQoL mea-
sures. We identified 441 meaningful concepts within
the generic and 538 within the stroke-specific mea-
sures. For both, generic and stroke-specific measures,
Table 3 Kappa coefficients and nonparametric bootstrapped 95% confidence intervals at the component, chapter, 2nd and 3rd ICF’s
levels for the three ICF components Body Function, Activity and Participation, and Environmental Factors
ICF Levels ICF Components Body Function Activity and Participation Environmental Factors
Components 0.81 [0.78;0.84]
Chapter Level 0.67 [0.58;0.76] 0.84 [0.80;0.87] 0.62 [0.48;0.81]
2nd Level 0.76 [0.69;0.85] 0.78 [0.78;0.81] 0.46 [0.24;0.72]
3rd Level 0.67 [0.63;0.73] 0.78 [0.78;0.79] 0.51 [0.26;0.79]
979
content concepts
113
not linked to the
ICF
866
linked to the
ICF
233
linked to
Body Functions
586
linked to
Activity and Participation
47
linked to
Environmental Factors
284
generic
35
generic
142
stroke-specific
91
generic
302
stroke-specific
12
stroke-specific
Fig. 2 Number of meaningful
concepts identified in the 13
HRQoL measures and their
distribution across the major
components of the ICF. The
component Body Structures is
not part of the figure, because
none of the measures
contained concepts that were
linked to this component
Qual Life Res (2007) 16:833–851 841
123

10. Table4ThenumberofidentifiedmeaningfulconceptsintheselectedHRQoLmeasuresandthenumberofdifferentICFcategoriesusedforlinkagedistributedbyICF
componentsandlevelsofhierarchy
TotalGenericHRQoLmeasuresStroke-specificHRQoLmeasures
SF-36RNLSIPEQ-5DLHSNHPSISSSQoLSAQoL-39QLI-SVSA-SIP30BOSSHSQuale
Numberofitems6203611136564559623972306554
Numberofmeaningfulconcepts
Total9795443213145562798450764482123
Peritem(contentdensity)1.61.53.91.62.89.21.41.31.41.31.11.51.32.3
ConceptslinkedtotheICFa
8664439205135059717948524164101
88%81%91%96%93%91%95%90%94%96%68%93%78%82%
ConceptsnotlinkedtotheICFa
11310481538522431822
12%19%9%4%7%9%5%10%6%4%32%7%22%18%
ICFcategoriesusedforlinkage
Total(number)200232910412473856523925323569
(bandwidth%,N=1454)*
14%2%2%7%1%3%3%4%4%3%2%2%2%5%
Perconcept(contentdiversity)0.200.430.670.490.860.850.610.710.620.780.330.730.430.56
PerICFcomponentb
BodyFunctions(n)553262810141712441117
(bandwidth%,N=493)*
11%1%5%<1%2%2%3%3%2%1%1%2%3%
ActivityandParticipation(n)12620236810362542352717252452
(bandwidth%,N=393)*
32%5%6%17%3%9%6%11%9%7%4%6%6%13%
EnvironmentalFactors(n)196103343
(bandwidth%,N=258)*
7%2%4%1%1%2%1%
PerlevelofICFhierarchy
1stlevel8212333322142
2ndlevel789154510261313241614151434
3rdlevel10914125718223824209161430
4thlevel5121133
Blankspacesmeannoentryinthisfield.
a
Percentagesarecalculatedbasedonthetotalnumberofconceptsforeachinstrument
b
ThefourthcomponentoftheICF,namelyBodyStructuresisnotpartofthetable,becausenoneoftheHRQoLmeasuresincludedmeaningfulconceptthathavebeenlinkedto
BodyStructures
*
PercentagesarecalculatedbasedonthetotalnumberofallexistingICFcategoriesshowninparenthesisasN
842 Qual Life Res (2007) 16:833–851
123

11. we used 150 different ICF categories for the linkage.
The bandwidth of content coverage is similar for gen-
eric and stroke specific measures.
Out of the 200 ICF categories used for the linkage of
the instruments’ meaningful concepts, 50 ICF categories
(25%) are only represented in the stroke-specific instru-
ments and 51 categories (25%) are only addressed in
generic measures. For example, specific memory func-
tions (e.g. ‘b1440 Short-term memory’, ‘b1441 Long-term
memory’, ‘b1442 Retrieval of memory’) or specific
mental functions of language (e.g. ‘b16700 Reception of
spoken language’, ‘b16701 Reception of written lan-
guage’, ‘b16710 Expression of spoken language’) are only
included in stroke-specific instruments, mainly in the SIS,
the BOSS, and the HSQuale. However, 13 out of the total
19 different ICF categories from the component Envi-
ronmental Factors are only included in generic measures,
mainly in the RNL and the SIP.
While the category ‘b152 Emotional functions’ has
the highest frequency within the generic as well as
Table 5 The 2nd-level ICF categories from the component Body Functions represented in the examined HRQoL measures
BODY FUNCTIONS Generic HRQoL measures Stroke-specific HRQoL measures
ICF Category SF-
36
RNL SIP EQ-
5D
LHS NHP SIS SS-
QoL
SA-
QoL-39
QLI-
SV
SA-
SIP30
BOSS HS
Quale
b1 Mental functions
b110 Consciousness functions +
b114 Orientation functions + + +
b117 Intellectual functions + +
b126 Temperament and personality
functions
+ + +
b130 Energy and drive functions + + + + + + + +
b134 Sleep functions + + +
b140 Attention functions + + +
b144 Memory functions + + + + + + +
b147 Psychomotor functions +
b152 Emotional functions + + + + + + + + + + +
b160 Thought functions +
b164 Higher-level cognitive functions + + +
b167 Mental functions of language + + + + +
b180 Experience of self and time
functions
+ +
b2 Sensory functions and pain
b210 Seeing functions + + +
b230 Hearing functions +
b280 Sensation of pain + + + + + +
b3 Voice and speech functions
b310 Voice functions +
b320 Articulation functions + + + +
b330 Fluency and rhythm of speech
functions
+ + +
b4 Functions of the cardiovascular, haematological, immunological and respiratory systems
b455 Exercise tolerance functions + + + + +
b5 Functions of the digestive, metabolic and endocrine systems
b510 Ingestion functions + + +
b525 Defecation functions + +
b6 Genitourinary and reproductive functions
b620 Urination functions + +
b640 Sexual functions + +
b7 Neuromusculoskeletal and movement-related functions
b730 Muscle power functions + +
b755 Involuntary movement reaction
functions
+ + + + +
b760 Control of voluntary movement
functions
+
b770 Gait pattern functions +
+ The ICF category is covered by the according HRQoL measure
Blank spaces mean no entry in this field
The results are summarized at the 2nd level of the ICF’s hierarchical structure
Qual Life Res (2007) 16:833–851 843
123

12. within the stroke-specific measures, the subsequent
categories differ between the two groups of measures.
Within the generic measures, we most frequently used
the categories ‘d2102 Undertaking a single task inde-
pendently’ (n = 15), ‘b280 Sensation of pain’ (n = 13),
‘d760 Family relationships’ (n = 13). Within the stroke-
specific measures, we most frequently applied the cat-
egories ‘d330 Speaking’ (n = 14), ‘d450 Walking’
(n = 11), and ‘b1300 Energy level’ (n = 11).
Differences also occur within the component of
Body Functions at the chapter ‘b1 Mental functions’.
ICF categories from this chapter are contained in 159
items of the 13 selected measures, in 57 items from
generic, and 102 items from stroke-specific instru-
ments.
In the ICF component Environmental Factors,
categories belonging to the chapter ‘e1 Products and
technology’ (e.g. including food, drugs or assistive
devices) are contained in 30 items of the 13 instru-
ments, in 25 items of the generic and 5 items of the
stroke-specific measures. However, concerning the ICF
component Activity and Participation no systematic
differences between the generic and the stroke-specific
measures are apparent.
Discussion
The present study provides an overview and compari-
son of current HRQoL measures in stroke with respect
to their covered contents using the ICF as an
independent, external reference system. The exami-
nation of the instruments’ contents relies on the
smallest possible units of content, namely on mean-
ingful concepts within the items. This gives a clear and
precise picture of the addressed contents of the
instruments and allows for straightforward compari-
sons. The results of the content comparison provide
valuable information to facilitate and account for the
selection of appropriate instruments for different pur-
poses of data collection in clinical as well as research
settings.
Researchers and clinicians who define the aspects
they want to measure in terms of the ICF can directly
use the Tables 5–7 to look up, which of the examined
HRQoL measures covers those aspects. For example, a
researcher dealing with the question of the effects of
muscle power training on the quality of life following
stroke will find the category ‘b730 Muscle power
functions’ in Table 6. In this table the researcher can
see that the SIS and the HSQuale address this area of
functioning and might therefore present an adequate
choice in this context.
Thus, using the ICF, the purpose of the investigation
and the content of assessment instruments can be
easily matched to each other. Thereby the selection of
instruments is facilitated. Methods for the linkage of
interventions [13], and a study applying the linkage to
nursing interventions are already available [6]. Also,
further studies presenting the linkage results of con-
dition-specific measures [7, 74, 76, 89], and of generic
quality of life instruments [14] have been published.
The examination of the 13 instruments’ content
structure revealed insights into the measures’ content
density, content diversity, and bandwidth of content
coverage, which are useful features for instrument
selection.
While the instruments differ by length and number of
concepts contained, based on the index of content den-
sity, the level of complexity of the instruments can be
compared. For example, for application in stroke sur-
vivors with cognitive and communication impairments,
instruments with lower levels of complexity might be
preferred (e.g. QLI-SV, SIS, SAQoL-39, BOSS).
The instruments differ by the number of concepts
they contain and the number of ICF categories used to
map these concepts. However, the index of content
diversity indicates the extent to which the instruments
are differentiated in a comparable way. The bandwidth
of content coverage can be used to compare the scope
of the instruments considering the addressed health
domains.
Instruments with a lower index of content diversity
(e.g. QLI-SV, BOSS, SF-36) might be more
differentiated and fine grained, including several con-
cepts related to the same topic. In contrast, measures
with a high content diversity (e.g. EQ-D5, LHS, SA-
QoL-39) may address their topics in a less differenti-
ated and more parsimonious way.
Instruments with a smaller bandwidth of content
coverage (e.g. EQ-D5, SF-36, QLI-SV) may be focused
on few but relevant health domains, while measures
with a greater bandwidth of content coverage contain
items across a higher number of different health do-
mains (e.g. SIP, HSQuale, SIS). Depending on the
special purpose of the instruments’ intended use, a
different type of instrument would be appropriate, e.g.
for surveys or individual decision-making.
Examining the representation of the instruments’
contents, it is remarkable that a high percentage of the
used ICF categories (40%) applied to only one of the
13 selected measures, respectively. This means that a
high number of topics is addressed in only one instru-
ment and no other instrument includes them. In this
way, some measures are uniquely appropriate for cer-
tain purposes. For example, the only instrument
844 Qual Life Res (2007) 16:833–851
123

13. Table 6 The 2nd-level ICF categories from the component Activity and Participation represented in the examined HRQoL measures
Activity and Participation Generic HRQoL measures Stroke-specific HRQoL measures
ICF Category SF-
36
RNL SIP EQ-
5D
LHS NHP SIS SS-
QoL
SA-
QoL-39
QLI-
SV
SA-
SIP30
BOSS HS
Quale
d1 Learning and applying knowledge + +
d110 Watching + + + + +
d160 Focusing attention + +
d163 Thinking + + + + + +
d166 Reading +
d170 Writing + + + +
d175 Solving problems + + +
d177 Making decisions + + +
d2 General tasks and demands
d210 Undertaking a single task + + + + + +
d220 Undertaking multiple tasks + + + +
d230 Carrying out daily routine + + + + + + +
d240 Handling stress and other
psychological demands
+
d3 Communication
d330 Speaking + + + + + + + +
d335 Producing nonverbal messages +
d340 Producing messages in formal sign
language
+
d345 Writing messages +
d350 Conversation + + + +
d360 Using communication devices and
techniques
+ + + + + +
d4 Mobility
d410 Changing basic body position + + + + + + + + +
d415 Maintaining a body position + + + + +
d420 Transferring oneself +
d430 Lifting and carrying objects + + +
d440 Fine hand use + + + + +
d445 Hand and arm use + + + + + +
d450 Walking + + + + + + + + + +
d455 Moving around + + + + + + + + +
d460 Moving around in different
locations
+ + + + + + +
d465 Moving around using equipment + + + +
d470 Using transportation + + + +
d5 Self-care
d510 Washing oneself + + + + + + + + + + +
d520 Caring for body parts + +
d530 Toileting + + + + + +
d540 Dressing + + + + + + + + + + + +
d550 Eating + + + +
d560 Drinking +
d570 Looking after one’s health + + +
d6 Domestic life
d620 Acquisition of goods and services + + + + +
d630 Preparing meals + + + + +
d640 Doing housework + + + + + + + + + + + +
d650 Caring for household objects + + + + + +
d660 Assisting others + + + +
d7 Interpersonal interactions and relationships
d710 Basic interpersonal interactions + +
d720 Complex interpersonal interactions + + + + +
d730 Relating with strangers +
d740 Formal relationships + +
d750 Informal social relationships + + + + + + + + + +
d760 Family relationships + + + + + + + + + + + +
d770 Intimate relationships + + + +
d8 Major life areas
Qual Life Res (2007) 16:833–851 845
123

14. addressing specific memory functions is the SIS. Con-
sequently, for the purpose of evaluating a memory
training program using a HRQoL measure, the SIS
might be a preferred choice.
By contrast, even the category with the overall
highest frequency, namely ‘b152 Emotional functions’
is not included in all instruments. For example, it is not
addressed in the RNL and the LHS, which thus might
Table 6 continued
Activity and Participation Generic HRQoL measures Stroke-specific HRQoL measures
ICF Category SF-
36
RNL SIP EQ-
5D
LHS NHP SIS SS-
QoL
SA-
QoL-39
QLI-
SV
SA-
SIP30
BOSS HS
Quale
d820 School education + + + +
d830 Higher education +
d845 Acquiring, keeping and
terminating a job
+
d850 Remunerative employment + + + + + + + + + +
d855 Non-remunerative employment + + +
d860 Basic economic transactions + +
d870 Economic self-sufficiency + + +
d9 Community, social and civic life
d910 Community life + + +
d920 Recreation and leisure + + + + + + + + + + + + +
d930 Religion and spirituality + + +
+ The ICF category is covered by the according HRQoL measure
Blank spaces mean no entry in this field
The results are summarized at the 2nd level of the ICF’s hierarchical structure
Table 7 The 2nd-level ICF categories from the component Environmental Factors represented in the examined HRQoL measures
Environmental Factors Generic HRQoL measures Stroke-specific HRQoL measures
ICF Category SF-
36
RNL SIP EQ-
5D
LHS NHP SIS SS-
QoL
SA-
QoL-
39
QLI-
SV
SA-
SIP30
BOSS HS
Quale
e1 Products and technology
e110 Products or substances for personal
consumption
+ +
e115 Products and technology for personal use in
daily living
+ +
e120 Products and technology for personal
indoor and outdoor mobility and
transportation
+ + + + +
e130 Products and technology for education +
e135 Products and technology for employment + +
e140 Products and technology for culture,
recreation and sport
+
e155 Design, construction and building products
and technology of buildings for private
use
+ + +
e2 Natural environment and human-made changes to environment
e240 Light + +
e3 Support and relationships + + + +
e310 Immediate family +
e325 Acquaintances, peers, colleagues,
neighbours and community members
+
e5 Services, systems and policies
e570 Social security services, systems and policies +
e580 Health services, systems and policies +
+ The ICF category is covered by the according HRQoL measure
Blank spaces mean no entry in this field
The results are summarized at the 2nd level of the ICF’s hierarchical structure
846 Qual Life Res (2007) 16:833–851
123

15. fall out of the selection pool when emotions are of
special interest.
A further important finding of this study refers to
the representation of Environmental Factors within the
selected measures. Only few measures involve the
influence of Environmental Factors, like assistive de-
vices or support, e.g. the RNL or the SIP. However, in
community rehabilitation settings for example, or for
use within the context of certain health professions, e.g.
in occupational therapy, instruments including Envi-
ronmental Factors might be preferred [77].
With regard to their content structure, no systematic
differences between generic and stroke-specific mea-
sures were found; however, we found differences
regarding content representation. Stroke-specific
measures more often address different mental func-
tions, than generic measures. Thus, when mental
functions following stroke are of special interest, an
appropriate instrument might rather be chosen from
the pool of stroke-specific measures. In contrast,
Environmental Factors are more often addressed in the
selected generic instruments. However, referring to
Activities and Participation no systematic difference
between generic and stroke-specific measures is
apparent.
Considering the most frequently used ICF catego-
ries we found further differences between the contents
of generic and the stroke-specific instruments. Within
the generic measures, independence, pain and family
relations are addressed most often. These are the areas
where the most burdensome problems may arise in
relation to a health condition. The most often
addressed areas within the stroke-specific measures,
i.e. walking, speaking and energy, represent the direct
impact of stroke on affected patients’ lives. This finding
supports the usefulness of the applied linkage proce-
dure as it clearly reflects the conceptual differences
between the generic and stroke-specific instruments.
The examination of the instruments’ content is one,
but essential, step among others in order to select an
appropriate measure. HRQoL represents a compre-
hensive construct and different HRQoL measures ad-
dress a wide variety of different health-related issues.
Thus, without knowing which areas a specific measure
covers, investigators cannot ensure the relevance of the
instrument’s contents to the purpose of measurement.
Table 8 The number of identified meaningful concepts in the selected HRQoL measures and the number of different ICF categories
used for linkage distributed by ICF components and levels of hierarchy, summarized for the generic and the stroke-specific HRQoL
measures
Generic Stroke-specific
Number of items 239 381
Number of concepts
Total 441 538
Per item (content density) 1.8 1.4
Concepts linked to the ICFa
410 456
93% 85%
Concepts not linked to the ICFa
31 82
7% 15%
ICF categories used for linkage
Total (number) 150 150
(bandwidth%, N = 1454)*
10% 10%
Per concept (content diversity) 0.34 0.28
Per ICF componentb
Body Functions (n) 34 41
(bandwidth%, N = 493)*
7% 8%
Activity and Participation (n) 99 103
(bandwidth%, N = 393) 25% 26%
Environmental Factors (n) 17 6
(bandwidth%, N = 258)*
7% 2%
Per level of ICF hierarchy
1st level 6 8
2nd level 66 57
3rd level 77 81
4th level 1 4
a
Percentages are calculated based on the total number of concepts for each instrument
b
The fourth component of the ICF, namely Body Structures is not part of the table, because none of the HRQoL measures included
meaningful concept that have been linked to Body Structures
*
Percentages are calculated based on the total number of all existing ICF categories shown in parenthesis as N
Qual Life Res (2007) 16:833–851 847
123

16. For the selection of an appropriate measure, further
essential criteria have to be considered. The suitability
of a measure depends not only on its content, but also
on further intrinsic characteristics of the instruments
(e.g. psychometric properties, feasibility, etc.), as well
as on external issues of the measurement context (e.g.
purpose, patients, setting, resources, etc.) [37, 73].
The ICF Research Branch at the University of
Munich and the WHO have recently developed inter-
nationally agreed ‘ICF Core Sets’ for various health
conditions [12], including stroke [40]. The ‘ICF Core
Set for Stroke’ represents a selection of ICF categories
to describe the typical spectrum of problems in func-
tioning among patients with stroke. This ‘ICF Core Set’
can be used to answer the question ‘‘what should be
measured in stroke?’’. Thus, a comparison between the
‘ICF Core Set for Stroke’ and the results of the ICF-
based content examination of instruments can be used
to support the selection of appropriate measures.
An ICF-based content examination of HRQoL
measures may serve further purposes other than the
selection of instruments. An ICF-based content
examination may facilitate the development of new or
modified measures. The ‘ICF Core Set for Stroke’ [40]
can be used to identify areas of stroke patients’ func-
tioning and health, which are scarcely captured by
existing measures. This can guide further instrument
development. Additionally, the content diversity and
density indices may point to measures with a potential
for refinements as to clarity or redundancy. Further-
more, they might be helpful in identifying measures
which due to their content structure, are readily suit-
able for translation into different languages and use in
international trials. Also, the ICF-based content
description of health-status measures may serve as a
first step for item banking and tailored testing [65].
In addition, the ICF-based content examination of
instruments may facilitate the further development of the
ICF, by identifying concepts not yet covered by the ICF.
Moreover, the possibility of a detailed content compari-
son of instruments may provide a new way to conduct
psychometric validity studies and explain their results.
The current study is subject to several limitations.
The systematic literature review used to identify
current HRQoL measures in stroke relied upon a
simplified review methodology, using specific rather
than sensitive search strategies. Moreover, we relied to
a large extent on information contained in the paper
abstracts. Still, compared with other reviews on mea-
sures in stroke [10, 18, 42, 90] the instruments identified
cover the most frequently used established HRQoL
measures and in addition, also include several recently
developed instruments.
Our study was concerned with HRQoL measures,
but does not deal with other important types of mea-
sures, like performance-based assessments of capacity.
Users of measures need to be aware of the conceptual
differences and the different results when they use self-
or interviewer-administered HRQoL measures versus
performance-based assessments.
We evaluated the linkage process by calculating
kappa coefficients, which showed satisfactory results
for linker agreement. Kappa is an often used and
simple indicator of agreement accounting for chance.
However, unsystematic error due to chance appears to
be of secondary relevance for the linkage procedure. In
the future, further analyses, e.g. using modelling
methods, would be useful to explain the disagreements
between the linkers (e.g. due to experience or profes-
sion) and to refine the linkage method.
Although the ICF has been criticized for lacking the
subjective dimensions of functioning and disability [81,
87], our results show that the ICF is able to represent
the contents of HRQoL measures.
In addition, in the items that contain concepts address-
ing aspects of the component Activity and Participation,
the differentiation between activity and participation was
not made. Moreover, the information whether a concept
addresses activity or participation from the perspective of
capacity or from the perspective of performance is also not
addressed. This represents a limitation of the linkage
procedure, which has already been considered [13]. In the
ICF, capacity is defined as the maximum level of func-
tioning adjusted for the influence of the environment.
Performance is defined as the level of functioning taking
into account the influence of the environment and the
individual’s involvement in life situations.
Finally, when interpreting the indices for content
diversity and bandwidth of content coverage, we imply
that the ICF is the accepted reference with its given
categories and its given levels of hierarchy. Thus, the
results of the content comparison of the selected
instruments only hold relative to this frame of refer-
ence. However, the ICF is expected to become the one
generally accepted framework to describe functioning
and health in all health-related fields [78].
Acknowledgements We thank Ms Edda Amann, MPH, ICF
Research Branch of the WHO FIC Collaborating Center
(DIMDI), IHRS, Ludwig-Maximilians-University, Munich,
Germany for her contribution to the linkage procedure.
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