1119
ORIGINAL ARTICLE
Development of a Set of Functional Hierarchical Balance Short
Forms for Patients With Stroke
Wen-Hsuan Hou, MD, MS, Jyun-Hong Chen, MS, Yen-Ho Wang, MD, Chun-Hou Wang, BS,
Jau-Hong Lin, PhD, I-Ping Hsueh, MA, Yu-Chih Ou, MS, Ching-Lin Hsieh, PhD
ABSTRACT. Hou W-H, Chen J-H, Wang Y-H, Wang C-H,
Lin J-H, Hsueh I-P, Ou Y-C, Hsieh C-L. Development of a set
of functional hierarchical balance short forms for patients with
stroke. Arch Phys Med Rehabil 2011;92:1119-25.
Objective: To develop a set of 3 hierarchical balance short
forms (HBSF; containing sitting, standing, and stepping forms)
to measure balance function in patients with stroke.
Design: First, we developed the HBSF, based on a previous
data set, with each short form containing 6 items. Second, we
examined the psychometric properties and efficiency of the
HBSF.
Setting: Six teaching hospitals.
Participants: Patients with stroke (n⫽764) for the first part
of this study; inpatients and outpatients (n⫽85) for the second
part of this study.
Interventions: Not applicable.
Main Outcome Measures: We used the item bank (9 sitting-related, 14 standing-related, and 13 stepping-related items)
from the Balance Computerized Adaptive Test to develop the
HBSF. Both the HBSF and the Berg Balance Scale (BBS) were
administered to patients, to determine the concurrent validity
and time needed for administration of both measures. Each
patient was assessed by 1 of the 3 short forms selected by a
rater.
Results: The reliability of the HBSF was relatively high
(reliability coefficients, .94 –.95). The scores of the HBSF were
highly correlated with those of the BBS (Spearman ␳⫽.80 –
.91), supporting the concurrent validity of the HBSF. The
average time needed to administer the HBSF was 122 seconds
(ie, about 40% of that for the BBS).
Conclusions: Our results provide sufficient evidence that the
HBSF is an efficient, reliable, valid, and practical way to
measure balance function in patients with stroke.
From the Department of Physical Therapy and Rehabilitation, E-Da Hospital and
I-Shou University, Kaohsiung (Hou); Department of Psychology, National Chung
Cheng University, Minhsiung Township, Chiayi County (Chen); School of Occupational Therapy, College of Medicine, National Taiwan University, Taipei (Hsueh,
Hsieh); Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, Taipei (Hsueh, Hsieh, Y-H Wang); School of Physical Therapy,
College of Medical Technology, Chung Shan Medical University, Taichung City
(C-H Wang); Department of Physical Therapy, College of Health Science, and
Department and Graduate Institute of Neurology, College of Medicine, Kaohsiung
Medical University, Kaohsiung (Lin); and Mackay Memorial Hospital, Department of
Rehabilitation, Taipei (Ou), Taiwan.
Supported by research grants from the National Science Council (NSC96-2314-B002-168-MY2) and the National Health Research Institute (NHRI-EX98-9512PI,
NHRI-EX99-9512PI).
No commercial party having a direct financial interest in the results of the research
supporting this article has or will confer a benefit on the authors or on any organization with which the authors are associated.
Reprint requests to Ching-Lin Hsieh, PhD, School of Occupational Therapy, College of
Medicine, National Taiwan University, 4F, No 17, Xuzhou Rd, Taipei 100, Taiwan,
e-mail: clhsieh@ntu.edu.tw.
0003-9993/11/9207-00041$36.00/0
doi:10.1016/j.apmr.2011.02.012
Key Words: Postural Balance; Psychometrics; Rehabilitation; Stroke.
© 2011 by the American Congress of Rehabilitation
Medicine
OR PEOPLE RECOVERING from stroke, changes in balF
ance ability are highly correlated with changes in functions
such as ambulation and activities of daily living. Measuring
1-5
balance function precisely and efficiently is useful when planning treatment strategies and assessing outcomes in patients
with stroke.6,7 However, traditional balance measures are not
perfectly suited to making precise and efficient assessments
partly because of the lengthy tests for patients with stroke.
Therefore, a precise and limited assessment burden measure for
assessing balance function in patients with stroke is crucial for
clinicians.1
Short-form evaluation is a potentially optimal choice of
efficient measurements in modern clinical settings. We have
developed 2 short forms of balance measures by reducing the
number of items and simplifying the response categories in the
Berg Balance Scale (BBS)8 and the Posture Assessment Scale
for Stroke (PASS).9 However, because of the limited number
of original items (14 for the BBS, 12 for the PASS), both short
forms sacrifice, to some extent, precision and discrimination
(eg, having floor and ceiling effects) to achieve efficient assessment.8,9 These sacrifices limit the utility of both short
forms in clinical settings.
Computerized adaptive testing (CAT) has been well justified
for efficient and precise assessment of health-related outcomes.10-17 CAT uses a computer to administer items to respondents and allows patients’ levels of function to be estimated as precisely as desired (ie, to reach a preset reliability
level). For example, if a patient cannot pass the item of “stand
independently,” the computer “knows” not to present any
harder item such as “walk” or “jump.” Instead, the next testing
item presented by the computer will be whether the patient can
“sit with or without assistance.” Because the testing items are
chosen on the basis of the patient’s performance, the resulting
score can achieve sufficient precision (reliability) with a minimal number of items.18 Therefore, CAT involves the use of a
computer to administer tailored items according to respondents’ abilities and allows respondents’ level of function to be
estimated with a preset, sufficient reliability.13,19
We have developed a Balance CAT18 with sufficient reliability and limited floor and ceiling effects for patients with
List of Abbreviations
BBS
CAT
HBSF
MAP
PASS
Berg Balance Scale
computerized adaptive testing
Hierarchical Balance Short Forms
maximum a posteriori
Posture Assessment Scale for Stroke
Arch Phys Med Rehabil Vol 92, July 2011
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DEVELOPING SHORT FORMS TO ASSESS BALANCE, Hou
stroke. However, the utility of a single-domain Balance CAT
may be restricted in daily clinics because the other important
assessments (eg, assessing motor, sensory, or activities of daily
living) have not yet been computerized and tailored for patient
management. Thus, clinicians may encounter difficulty in using
and integrating both CAT and traditional measures. Thus, a
precise and efficient balance measure using traditional testing
is still needed for clinicians.
A CAT is developed on the basis of a large number of items,
or an item bank. The item bank is useful for developing short
forms without sacrificing substantial psychometric properties
(eg, reliability, floor and ceiling effects). Thus, several short
forms based on item banks have been developed to improve
efficiency with sound psychometric properties in the assessments of physical function,20 activities,21-23 and health-related
quality of life.24 However, no short forms have been constructed on the basis of an established balance item bank for
patients with stroke to enhance clinical feasibility and efficiency. The purpose of this study was to develop a set of
balance short forms by adopting items from the previously
developed Balance CAT18 to achieve reliable, valid, and efficient assessment of balance function in patients with stroke.
METHODS
The study consisted of 2 parts. In the first part, we used the
34 items of the Balance CAT18 (table 1) as the basis to develop
Table 1: Item Numbers, Contents, and Parameters of Original 34-Item Balance CAT and 3 Short Forms of HBSF (Sitting, Standing, and
Stepping) (Nⴝ764)
Item Parameter
Item No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
Item Content
Sitting with trunk support for 10 seconds (on a chair with a
back rest)
Sitting without trunk support for 10 seconds
Reaching for a pen on the less affected side and putting it into
a chest pocket on the more affected side
Reaching for a pen on the more affected side and putting it
into a chest pocket on the less affected side
Using the less affected leg to lift the more affected leg from
the ground for 5 seconds
Picking up a pen on the floor (in front of the less affected leg)
Picking up a pen on the floor (centered in front of the patient)
Sitting to supine
Sitting to standing
Supine to sitting
Standing with support for 10 seconds
Standing without support for 10 seconds
Standing without support and with eyes closed for 10 seconds
Turning the body to the more affected side to pick up a pen
Picking up a pen on the floor (in front of the less affected leg)
Maintaining a stride posture for 10 seconds (more affected leg
forward, knee bent)
Picking up a pen on the floor (centered in front of the patient)
Standing with feet together for 10 seconds
Maintaining in a stride posture for 10 seconds (less affected
leg forward, knee bent)
Picking up a pen on the floor (in front of the affected leg)
Standing with feet together and with eyes closed for 10
seconds
Marching in place
Standing on only the less affected leg
Standing heel to toe, more affected foot forward
Standing to squatting
Maintaining a squatting position
Squatting to standing
Standing on tiptoe
Tapping alternate feet
Jumping vertically with both legs
Standing heel to toe, less affected foot forward
Standing on only the more affected leg
Hopping in place on the less affected foot
Hopping in place on the more affected foot
Balance Level
Slope
Step 1*
Step 2*
Sitting
2.72
–2.39
NA
Sitting
Sitting
4.67
3.82
⫺1.76
⫺1.54
NA
NA
Sitting
3.64
⫺1.29
NA
Sitting
1.52
⫺1.05
NA
Sitting
Sitting
Sitting
Standing
Standing
Sitting/standing
Standing
Standing
Standing
Standing
Standing
2.38
2.50
1.32
1.90
1.30
3.96
5.76
4.09
3.51
4.16
4.40
⫺1.03
⫺0.87
⫺0.66
⫺0.11
⫺0.21
⫺0.77
⫺0.53
⫺0.29
0.02
0.10
0.13
NA
NA
⫺0.06
0.12
0.12
NA
NA
NA
NA
NA
NA
Standing
Standing
Standing
4.17
4.57
4.85
0.14
0.17
0.26
NA
NA
NA
Standing
Standing
3.35
2.93
0.27
0.28
NA
NA
Standing/stepping
Stepping
Stepping
Stepping
Stepping
Stepping
Stepping
Stepping
Stepping
Stepping
Stepping
Stepping
Stepping
3.02
2.16
2.75
3.86
3.93
3.86
1.87
1.86
3.15
2.88
2.00
2.59
2.98
0.50
0.55
0.88
0.97
0.98
1.05
0.82
1.07
1.09
1.11
0.91
1.26
1.86
NA
1.02
NA
NA
NA
NA
1.31
NA
NA
NA
1.88
1.66
2.17
NOTE. Words in boldface represent the items chosen for the final set of HBSF at each balance level. The items are generally arranged in
increasing order of difficulty.
Abbreviation: NA, not applicable.
*Step difficulty means the threshold between adjacent response categories.
Arch Phys Med Rehabil Vol 92, July 2011
DEVELOPING SHORT FORMS TO ASSESS BALANCE, Hou
Fig 1. Flowchart of the procedures to develop the HBSF.
a set of short forms, named the Hierarchical Balance Short
Forms. Second, we investigated the concurrent validity, efficiency, and floor and ceiling effects of each HBSF. This study
was approved by the institutional review boards of the National
Taiwan University Hospital.
Develop the Hierarchical Balance Short Forms
Figure 1 depicts the 3 steps for develping the Hierarchical
Balance Short Forms (HBSF), which are as follows:
Step 1: Divide original 34-item bank into 3 hierarchical,
function-related balance levels. The Balance CAT is a CAT
system currently in development for assessing balance function
in patients with stroke.18 Traditional balance measures have
been criticized for being time-consuming and involving complicated tasks; however, our Balance CAT is being developed
from a well-calibrated item bank on the basis of balance
concepts in daily tasks and activities (ie, the ability to maintain
a given posture and the ability to ensure equilibrium while
changing position).25 Of the 34 items shown in table 1, 26
items are dichotomous (able or unable to perform a balancerelated task), and the other 8 are trichotomous categorical items
(ie, 0: unable, 1: able to complete the task but not smoothly,
and 2: able to complete the task smoothly; alternatively, 0:
unable, 1: able to maintain balance while performing a task for
1–5s, and 2: able to maintain balance while performing a task
for more than 5s).18 The items can be arranged into 3 hierarchical, function-related balance levels, from easy to hard, containing 9 sitting-related, 14 standing-related, and 13 steppingrelated items, respectively.
To ensure scale continuity between adjacent balance levels,
2 items were assigned to 2 adjacent levels (ie, item 11: “standing with support for 10 seconds” for sitting and standing levels;
item 22: “marching in place” for standing and stepping levels).
Both items were selected according to the item contents and
item difficulty (see table 1).
Step 2: Propose 6 candidates for each balance level. To
determine the most appropriate candidate short forms for the
HBSF, a Fortran program written by the authors was used to
perform a simulation using the actual data of the 764 patients
with stroke that were originally used to develop the Balance
CAT.18 We used the generalized partial credit model26 to fit our
1121
data and to estimate the item parameters for the item bank.
Maximum Fisher information was used as the item selection
algorithm, and the maximum a posteriori (MAP) method was
used to estimate the patients’ ability. In addition, we calculated
the conditional reliability (the inverse of the observed score’s
SE at any given test score)27 of each patient, and each candidate (6 items) of the HBSF was estimated for its average
reliability, SE, maximum-minimum balance score, scoring
range, and correlation with the 34-item bank.
We first determined the number of items for the HBSF. Our
previous study18 has shown that the Balance CAT takes 4
items, on average, to reach sufficient reliability (0.9), while it
takes 6 items to reach excellent reliability (.95). The reliability
coefficient was set at above 0.9 for the HBSF because it is a
common standard for individual comparison.28 Nevertheless,
to ensure sufficient reliability, we added 2 more items to the
HBSF (6 items each) than to the Balance CAT (4 items). In
addition, we designed a set of 3 hierarchical short forms to
increase the suitability of items for different balance levels of
patients. Thus, we proposed 6 candidates in each balance level
with the highest reliability, using the simulation on the item
parameters (slope and steps threshold) obtained previously (see
table 1).18
The item-selection principles focused on the most reliable
and discriminative candidates (short forms) to achieve both
reliability and discrimination. Therefore, we extracted the 3
candidates with the highest reliability to achieve sufficient
reliability, and the other 3, including the most difficult and
easiest items, simultaneously to enhance the discriminability of
estimation for patients with extreme balance ability. Using
sitting level as an example, shown in figure 1, we first determined candidates 1 to 3 by selecting 6 items from the 9
sitting-related items (C69) with the highest reliability (step 2-1).
Then we further determined candidates 4 to 6 by first selecting
the 2 items with the greatest difficulty (item no. 11) and the
least difficulty (item no. 2), and then chose the other 4 items
from the rest of the 7 sitting-related items (C6⫺29⫺2) (step 2-2).
We adopted the 2 items with greatest difficulty (item no. 11)
and least difficulty (item no. 2) in order to broaden the range of
the estimation value of balance function. In addition, we selected the subsequent 4 items of intermediate difficulty to
increase the reliability. We took these steps so that the most
discriminative items would be distributed evenly within this
range, which would provide similar results of selecting items
along the difficulty continuum. Consequently, a total of 18
candidates (each with 6 items) belonging to 3 different balance
levels were selected.
The participants’ responses on the 34 items were used for
simulation.18 In the simulation, we assumed that the patients
would respond in the same way to the items, regardless of the
context. The 764 patients were divided into 3 groups (185, 310,
and 269 of sit, stand, and step groups, respectively) corresponding to their balance level, and their responses were used
to examine the psychometric properties of each candidate.
Therefore, the candidates in the sitting level were simulated on
the 185 patients who failed the item “standing with support for
10 seconds.” The candidates in the stepping level were simulated on the 310 patients who passed the item “marching in
place.” The candidates in the standing level were simulated on
the other 269 patients. The balance function of each patient and
its reliability were calculated for all candidates. The MAP
method was adopted in this study for consistency, as in the
previous Balance CAT study.18
Step 3: Determine an optimal set of Hierarchical Balance
Short Forms. We adopted the opinions of experienced
stroke-related clinicians (1 physiatrist, 3 senior occupational
Arch Phys Med Rehabil Vol 92, July 2011
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DEVELOPING SHORT FORMS TO ASSESS BALANCE, Hou
balance measure for patients with stroke.18,29,30 These items are
based on a 5-level scale (0 – 4). Its total score ranges from 0 to
56. Because the BBS is a commonly used balance measure in
patients with stroke, and has satisfactory psychometric properties (including reliability, validity, and responsiveness),8,31-33
we used the BBS as our criterion to validate the HBSF.1
Data analysis. The Spearman rank correlation coefficient
was used to examine the relationships between the scores of the
BBS and HBSF to determine the concurrent validity of the
HBSF. We first examined the relationships between all 85
patents’ scores on the HBSF and those of the BBS. We also
examined the relationships between the patients’ scores on
each short form of the HBSF (27 patients on the sitting, 29 on
the standing, and 29 on the stepping short forms) and the
corresponding BBS scores. Correlation coefficients greater
than 0.6 indicate acceptable concurrent validity.34 We also
examined the floor and ceiling effects of both the BBS and the
HBSF.
therapists, 1 physical therapist) and psychometricians (1 senior
expert in item response theory, 1 doctoral student studying
psychometrics).The clinicians mainly considered ease of use as
the most important issue, whereas the psychometricians mainly
considered psychometric properties (ie, reliability, SE, scoring
range, and correlation with the Balance CAT). Disagreements
between clinicians and psychometricians were arbitrated by a
consensus conference to determine a final set of HBSF containing a 6-item balance short form for each sitting, standing,
and stepping level.
Concurrent Validity and Efficiency of the Hierarchical
Balance Short Forms
Sample. We invited inpatients and outpatients at 6 teaching hospitals in Taiwan to participate in our study. The following criteria were used to determine whether patients could be
included in this study: (1) first or recurrent onset of cerebrovascular accident; (2) unilateral or bilateral hemiparesis/hemiplegia; (3) Mini-Mental Status Examination score above 23
with the ability to follow instructions to complete the assessments; and (4) informed consent given personally or by proxy.
We excluded patients with other major diseases (eg, severe
rheumatoid arthritis) that might affect their balance ability.
Procedure. We administered both the HBSF and the BBS
to the patients. Each patient was assessed using 1 of the 3 short
forms (sitting, standing, or stepping) of the HBSF, which was
selected by an occupational therapist according to patients’
self-reports and the therapist’s judgment. The occupational
therapist was experienced, having administered all items of the
item bank of the Balance CAT to more than 200 patients. The
BBS was administered independently within 24 hours by another rater. The order of administrations was counterbalanced
to eliminate possible learning or fatigue effects. The raters did
not inform each other of their assessment results during the
study periods. We also recorded the time needed to administer
each short form of the HBSF and the BBS individually.
Measure. The BBS (including 1 sitting item and 13 standing items) has been identified as the most commonly used
RESULTS
Three Steps to Develop an Optimal Set of Hierarchical
Balance Short Forms
Table 1 shows the item contents and parameters chosen for
the HBSF (in boldface). Table 2 shows the 6 candidates with
the highest reliabilities of each balance level selected by simulation and the aforementioned preset rules. Both the psychometricians and clinicians reached consensus on the final set of
HBSF, shown in boldface in table 2. In the simulation study,
we further compared the scores obtained from the 3 short forms
of the HBSF and a 34-item bank of the same patients. Table 2
shows that the sitting short form had extremely high correlation
with the full item bank (Pearson r⫽.98), while both the standing and the stepping short forms had sufficiently high correlations (r⬎.91).
Reliability. The simulation study showed that the estimated score for patients using the final set of the HBSF all
reached sufficient average reliability (ⱖ.93) (fig 2, appendix 1).
Table 2: Included Items, Reliability, SE, Scoring Range, and Correlation With Full Bank of Candidate Short Forms by Sitting, Standing,
and Stepping (Nⴝ764)
Balance Level
Candidate
Included Item Nos.*
Average
Reliability
SE
Scoring Range†
(Maximal – Minimal Score)
Correlation With
34-Item Bank
Sitting
Sitting
Sitting
Sitting
Sitting
Sitting
Standing
Standing
Standing
Standing
Standing
Standing
Stepping
Stepping
Steeping
Stepping
Stepping
Stepping
1
2
3
4
5
6
1
2
3
4
5
6
1
2
3
4
5
6
1, 2, 4, 5, 7, 11
1, 3, 4, 5, 7, 11
1, 2, 3, 5, 7, 11
2, 3, 4, 5, 7, 11
2, 4, 5, 6, 7, 11
2, 3, 5, 6, 7, 11
9, 11, 12, 19, 20, 22
9, 11, 12, 18, 21, 22
9, 11, 12, 20, 21, 22
11, 12, 13, 15, 20, 22
11, 12, 13, 17, 18, 22
11, 12, 13, 15, 18, 22
22, 23, 24, 26, 28, 34
22, 23, 24, 27, 28, 34
22, 23, 25, 28, 32, 34
22, 23, 24, 26, 28, 33
22, 23, 24, 25, 28, 33
22, 23, 24, 28, 32, 33
.94
.93
.93
.95
.94
.94
.96
.95
.95
.96
.96
.96
.95
.95
.95
.95
.95
.95
.25
.26
.26
.23
.24
.24
.21
.21
.21
.19
.19
.19
.23
.23
.22
.22
.22
.23
3.42 (3.45–.03)
3.41 (3.45–.04)
3.40 (3.42–.02)
2.53 (3.45–.92)
2.57 (3.54–.97)
2.60 (3.52–.92)
2.42 (6.08–3.66)
2.37 (6.03–3.66)
2.42 (6.08–3.66)
2.24 (5.91–3.67)
2.18 (5.85–3.67)
2.16 (5.83–3.67)
3.95 (9.81–5.86)
3.94 (9.81–5.87)
4.09 (9.94–5.85)
3.15 (8.99–5.84)
3.15 (8.99–5.84)
3.59 (9.39–5.80)
.98
.98
.98
.97
.97
.96
.93
.90
.91
.92
.93
.92
.95
.95
.95
.93
.94
.91
NOTE. Words in boldface represent the final set of HBSF.
*The item numbers are derived from the original 34-item Balance CAT shown in table 1.
†
The scoring range means the maximum score minus the minimum score.
Arch Phys Med Rehabil Vol 92, July 2011
DEVELOPING SHORT FORMS TO ASSESS BALANCE, Hou
Fig 2. Reliability of the HBSF under different balance ability in
patients with stroke. Note that the original balance scores were
linearly transformed to 0 to 10 for ease of interpretation. Also, each
plot in the figure means different response patterns of the HBSF.
The reliability of most (about 96%) of the patients was above
0.9, and only patients who failed to perform all items of the
sitting short form and passed all items of the stepping short
form had reliabilities of .86 (see fig 2). The raw scores were
calculated from the sum of the 6-item response pattern shown
in appendix 1. The balance score transformation table from the
raw score of the final set of the HBSF in appendix 1 is provided
for the prospective users to obtain the corresponding estimation
of patients’ balance scores and reliabilities according to the
performance on each item. Figure 2 plots the continuum of
patients’ balance level (transformed scores, 0 –10) against reliability among the final set of HBSF. Except for patients with
extremely good and poor balance abilities, the average reliability of the HBSF achieved .93 and above.
Concurrent Validity and Efficiency of the Hierarchical
Balance Short Forms
Concurrent validity. A total of 85 patients with a mean
age ⫾ SD of 64.2⫾12.1 years participated in this part of the
study. Among them, 55 were men, 39 had left hemiparesis, and
58 sustained first or recurrent ischemic strokes and had had
stroke for 4.2⫾5.3 months. Twenty-seven patients completed
the sitting short form, 29 the standing short form, and 29 the
stepping short form. These patients had BBS scores throughout
the entire range (mean ⫾ SD, 22.9⫾19.2), indicating that they
had a wide range of balance function.
All 85 patients’ scores on the HBSF were highly correlated
with those of the BBS (Spearman ␳⫽.97). The scores of the
sitting (27 patients), standing (29 patients), and stepping (29
patients) short forms, individually, were also highly associated
with the total score of the BBS (Spearman ␳⫽.80, .91, and .84,
respectively). In addition, on the BBS, 8 patients (9.4% of the
85 patients) achieved the minimum scores of 0 points, and 4
patients (4.7%) achieved the maximum scores of 56 points,
representing a 14.1% floor-plus-ceiling effect, whereas on the
HBSF, only 5 (5.9%) patients obtained the minimum scores of
.03, and 2 (2.4%) obtained the maximum scores of 9.30,
representing an 8.2% floor-plus-ceiling effect.
Efficiency. The average time (122s) needed to administer
each short form of the HBSF was 40% of that of the BBS. The
average times needed for the sitting, standing, and stepping
short forms were 116, 122, and 128 seconds, respectively.
DISCUSSION
Our results showed that after patients were divided by their
balance level into sitting, standing, and stepping groups, only 6
1123
items were needed for each group of patients to achieve a
highly reliable and valid balance function assessment. The
scores obtained from each short form of the HBSF were not
only closely associated with those of the 34-item set of the
Balance CAT, but also highly correlated with those of the BBS,
supporting the concurrent validity of the HBSF. The average
time to administer the HBSF was only 40% of that for a
commonly used balance measure, the BBS. Hence, the HBSF
is efficient, reliable, valid, and practical for patients with
stroke.
The HBSF is worthy of clinical application because of the
following 3 special characteristics. First, the HBSF is simple
and quick to administer. There are only 6 items of easy-toadminister tasks in each short form. Patients are only tested in
limited postural changes (eg, 3 postures, including sitting to
standing, standing, and standing with trunk forward bending,
are required to administer the standing short form), which will
save administration time and reduce the burden. Second,
the psychometric properties (ie, reliability and validity) of the
HBSF are satisfactory and comparable to those of the Balance
CAT.18 The high correlations may be due to our dividing the
patients into 3 hierarchical groups by their balance level. Although the range of each HBSF is restricted, the HBSF showed
sufficient reliability in each of the 3 balance levels. Third, the
results of the HBSF appear useful in representing patients’
balance level (or milestone) and setting task-oriented goals of
clinical treatments. Because the HBSF is derived from the item
bank of the Balance CAT, the scores of both balance level and
functional descriptions can be obtained simultaneously by the
HBSF, which can help clinicians to obtain both the patients’
balance ability and performance on the hierarchical functional
tasks. From both clinicians’ and patients’ points of view, it is
a convenient way to monitor the milestone recovery from
sitting, standing, to stepping with patients’ balance scores. In
addition, the detailed functional descriptions (ie, “reaching for
a pen on the affected side and putting it into a chest pocket on
the affected side” or “standing on tiptoe”) are useful in setting
task-oriented goals and designing training strategies by observing patients’ difficulty in performing each task of the HBSF.
The BBS is the most commonly used balance measure for
patients with stroke.8,29 Our results showed that the HBSF
outperformed the BBS in 2 aspects, in addition to the efficiency
aforementioned. First, the HBSF substantially reduced floorplus-ceiling effects (only 8.2% in the HBSF, as compared to
14.1% in the BBS), indicating better discriminative ability for
patients with extreme balance ability. Second, the materials (ie,
bed, chair, and pen) needed for administering the HBSF are
few and easy to prepare. However, the BBS requires a step or
a stool, which might not be available in some clinics or wards.
These advantages support the utility of the HBSF.
We have successfully developed a Balance CAT system
that is useful to achieve precise and efficient assessment of
balance function. Two reasons inspired us to develop the
HBSF. First, the materials used for administrating the HBSF
(ie, paper, pen, chair, and bed) are accessible and available
in clinical settings, while the Balance CAT has to be administered via computer (or personal digital assistant) and
the Internet.18 The software and hardware are not accessible
in some stroke rehabilitation settings, limiting the utility of
the CAT system. Secondly, multidimensional measures are
essential for patient management and outcome measurement
in both clinical and research settings. However, only a few
well-developed CAT systems exist currently to replace the
traditional measures for patients with stroke. It is still troublesome and inconvenient to administer a single CAT system because researchers have yet to develop CATs for most
Arch Phys Med Rehabil Vol 92, July 2011
1124
DEVELOPING SHORT FORMS TO ASSESS BALANCE, Hou
of the domains (eg, mobility, mood, cognition, activities of
daily living, or even health-related quality of life) needed for
patient management in daily clinics. Thus, we are still far
from wide application of CATs at this stage. Finally, the test
results of the HBSF can be compared with those of the
Balance CAT because they were both developed on the basis
of the same scale by item response theory modeling. Therefore, the HBSF and Balance CAT can be used interchangeably.
Study Limitations
Two limitations might concern the readers. First, some
important psychometric properties (eg, responsiveness,35 the
minimal important difference36,37) of the HBSF remain unknown. Additional follow-up studies to examine the responsiveness and the minimal important difference are needed to
further establish the utility of the HBSF in both clinical and
research settings.36,37 Second, our prospective raters might
find difficulty in selecting the most appropriate short form
for patients. The raters might select an inappropriate short
form for patients. We suggest that the raters use another
short form of the HBSF if they find any conditions as
follows: patients originally categorized as in the sitting
group obtaining the highest score (passing all 6 items of the
sitting short form); those in the standing group having either
the highest or lowest scores (passing or failing all 6 items of
the standing short form); or those in the stepping group
getting the lowest score (failing all 6 items of the stepping
short form). In addition, future users can use the overlapping
items (“standing with support for 10 seconds” for sitting and
standing levels; “marching in place” for standing and stepping levels) as screening items to determine the most appropriate short form to administer.
CONCLUSIONS
Our results provide sufficient evidence that the HBSF is
an efficient, reliable, valid, and practical way to measure
balance function in patients with stroke. These results suggest that the HBSF is promising and convenient for measuring balance function in patients with stroke, and for
clinicians and researchers.
APPENDIX 1: BALANCE SCORE
TRANSFORMATION TABLE OF THE
HIERARCHICAL BALANCE SHORT FORMS FOR
PROSPECTIVE USERS
Response Pattern
Short
Form
Sitting
Standing
Item Item Item Item Item Item Balance
1
2
3
4
5
6
Score Reliability SE
0
1
1
1
1
1
1
0
0
0
1
2
2
2
0
0
1
1
1
1
1
0
1
1
1
1
1
1
0
0
0
1
1
1
1
0
0
1
1
1
1
1
0
0
0
0
1
1
1
0
0
0
0
0
1
1
0
0
0
0
0
1
1
0
0
0
0
0
0
1
0
0
0
0
0
0
1
0
0
0
0
0
0
0
Arch Phys Med Rehabil Vol 92, July 2011
0.03
1.06
1.93
2.69
2.99
3.45
3.36
3.45
3.66
4.35
4.78
5.14
5.71
6.08
.86
.94
.94
.94
.95
.95
.97
.95
.97
.95
.93
.96
.97
.95
.38
.25
.25
.24
.23
.23
.18
.23
.18
.23
.26
.21
.17
.21
APPENDIX 1: BALANCE SCORE
TRANSFORMATION TABLE OF THE
HIERARCHICAL BALANCE SHORT FORMS FOR
PROSPECTIVE USERS (Cont’d)
Response Pattern
Short
Form
Stepping
Item Item Item Item Item Item Balance
1
2
3
4
5
6
Score Reliability SE
2
0
1
1
1
1
1
1
1
1
1
1
1
0
0
1
1
1
1
2
2
2
2
2
1
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
1
1
1
1
1
2
2
2
1
0
0
0
0
0
1
1
1
1
1
2
1
0
0
0
0
0
0
0
1
1
2
2
6.14
6.08
6.14
6.20
6.48
6.87
7.14
7.44
7.84
8.16
8.71
9.39
.95
.95
.95
.95
.96
.96
.96
.96
.95
.95
.93
.86
.22
.21
.22
.21
.20
.20
.20
.20
.21
.23
.27
.37
NOTE.
1. Use of this table requires the administration of all 6 items in each
of the short forms.
2. Our principle of the above response patterns is based on the
hierarchy of item difficulty.
3. 0, 1, and 2 represented the raw score of response among each
item.
4. This table lists more than 80% of the response patterns. If a
patient’s response pattern is different from the above, please
download the detailed transform table (http://homepage.ntu.
edu.tw/⬃clhsieh/HBSF.xls) to estimate his/her balance score.
5. Because the most difficult item is not contained in the stepping
short form, patients who pass all items will not obtain scores
of 10.
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