Evaluation of the American Heart Association Stroke
Outcome Classification
Sue-Min Lai, PhD, MS, MBA; Pamela W. Duncan, PhD, PT
Downloaded from http://stroke.ahajournals.org/ by guest on June 16, 2017
Background and Purpose—The purpose of this study was to evaluate the concurrent validity of the American Heart
Association Stroke Outcome Classification (AHA.SOC) and compare performance of its function classification with that
of the Modified Rankin Scale.
Methods—The individuals in this study included the last 105 consecutive subjects who were part of a cohort of 459 stroke
patients in the Kansas City Stroke Study. The patients were evaluated with a variety of standardized assessments at
enrollment (within 14 days of stroke onset) and followed at 1, 3, and 6 months after stroke. Specifically, we examined
validity of AHA.SOC by comparing its 3 domains (ie, Domain, Severe, and Function) with stroke severity. We
correlated AHA.SOC-Function with scores of the Barthel Index, Lawton Instrumental Activities of Daily Living (IADL)
Scale, and Medical Outcome Study 36-Item Short-Form Health Survey (SF-36) measures of physical function and
mental health. Finally, we compared the discriminant ability of AHA.SOC-Function and the Modified Rankin Scale in
assessing disability and handicap. These data were analyzed with the use of Spearman rank correlations and
Kruskal-Wallis tests.
Results—All 3 domains of the AHA.SOC were significantly associated with stroke severity and scores of Barthel Index,
Lawton IADL, and SF-36 physical function (all P,0.001). Both AHA.SOC-Function and the Modified Rankin Scale
discriminated well the disabilities and handicap measured by Barthel Index, Lawton IADL, and SF-36 physical function
(all P,0.001).
Conclusions—The AHA.SOC was able to capture impairments, disabilities, and handicap after stroke. The AHA.SOCFunction performed equally as well as the Modified Rankin Scale in assessing disabilities related to basic activities of
daily living but differentiated slightly better than the Modified Rankin Scale in assessing disabilities/handicap related
to instrumental activities of daily living. Neither the AHA.SOC-Function nor the Modified Rankin Scale captured
differences in mental health after stroke. (Stroke. 1999;30:1840-1843.)
Key Words: activities of daily living n disability evaluation n outcome assessment n stroke
A
multidisciplinary panel recently created a new stroke
outcome classification: the American Heart Association
Stroke Outcome Classification1 (AHA.SOC). The new classification was developed to measure the full range of domains
affected by stroke. This new stroke outcome classification has
been shown to be a reliable (specifically, interrater reliability)
global classification system that summarizes the neurological
impairments, disabilities, and handicaps that occur after
stroke.1 The classification schema, which has 3 components,
identifies the number of affected neurological domains
(AHA.SOC-Domain), identifies the severity of impairments
(AHA.SOC-Severity), and classifies poststroke functional
disabilities and handicap (AHA.SOC-Function).
The Modified Rankin Scale is the most commonly used
outcome classification scale for disabilities and handicap after
stroke.2–7 The Modified Rankin Scale,2 which was adopted from
the Original Rankin Scale,8 has 6 grades ranging from grade 0
(no symptoms at all) to grade 5 (severe disability). The Original
Rankin Scale was a 5-point rating scale that did not contain
grade 0 and defined grade 1 as “no significant disability.”
Descriptions for grades 2 to 5 remained the same in both the
Original and Modified Rankin scales. Although the Modified
Rankin Scale has been evaluated with satisfactory results for its
reliability and reproducibility, relatively little is known about its
validity.5,9,10 One of the main objections to the Modified Rankin
Scale is that it rates disability rather than handicap.10 –12 Subsequently, the Modified Rankin Scale was further changed by
introducing the term lifestyle into the definitions for use in the
Oxfordshire Community Stroke Study12 to accommodate language disorder and cognitive defects. The word disability in the
Modified Rankin Scale was replaced with handicap to assess
lifestyle. Even with this modification, the Oxfordshire Handicap
Scale was again shown to be a global functional index rather
than a handicap measure. With this in mind, the AHA.SOC was
Received May 20, 1999; final revision received June 17, 1999; accepted June 17, 1999.
From the Department of Preventive Medicine (S-M.L.), Center on Aging (S-M.L., P.D.W.), and Department of Health Policy and Management
(P.W.D), University of Kansas Medical Center, Kansas City, Kan, and Department of Veteran Affairs Medical Center, Kansas City, Mo (P.W.D.).
Correspondence to Sue-Min Lai, PhD, MS, MBA, Department of Preventive Medicine, University of Kansas Medical Center, 3901 Rainbow Blvd,
Kansas City, KS 66160-7313. E-mail [email protected]
© 1999 American Heart Association, Inc.
Stroke is available at http://www.strokeaha.org
1840
Lai and Duncan
developed to expand the classification of stroke outcomes to
include handicap.
The purpose of this study was to compare the Modified
Rankin classification scale with the newly developed
AHA.SOC. Specifically, we examined the classification scales
by degree of stroke severity. Second, we correlated outcome
classifications with the Barthel Index,13 Lawton Instrumental
Activities of Daily Living (IADL),14 and Medical Outcome
Study 36-Item Short-Form Health Survey (SF-36)15 measures of
physical function and mental health. Finally, we compared the
discriminant ability of AHA.SOC-Function and the Modified
Rankin Scale in assessing disability and handicap.
Subjects and Methods
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The individuals for this study included the last 105 consecutive
subjects who were part of a cohort of 459 stroke patients in the
Kansas City Stroke Study. The participants were recruited from any
of 12 participating hospitals in the greater Kansas City area. Details
on subject eligibility and recruitment have been described in a
previous report.16 To be accepted into this study, the subject had to
have a confirmed eligible stroke, defined by World Health Organization criteria17 as of “rapid onset and of vascular origin reflecting a
focal disturbance of cerebral function, excluding isolated impairments of higher function and persisting longer than 24 hours.” The
stroke was confirmed by clinical assessment and/or by a CT/MRI
scan. Trained nurses/physical therapists reviewed medical records
and interviewed both patients and physicians to determine whether
the patient was eligible and had consented to enrollment. The
patients were evaluated with a variety of standardized assessments at
enrollment (within 14 days of stroke onset) and followed at 1, 3, and
6 months after stroke by a study nurse/physical therapist at home or
at a chronic care facility. Therefore, assignment of the AHA.SOC
and Rankin classifications was done with knowledge of the results
from these standardized assessments. For the present study, assessments that included baseline demographics, stroke characteristics,
Orpington Prognostic Scale18 (OPS), AHA.SOC,1 Modified Rankin
Scale,2 Barthel Index,13 Lawton IADL,14 SF-36 physical functioning
index15 (PFI), and SF-36 mental health index15 (MHI) were analyzed.
AHA.SOC-Domain records the number of affected neurological
domains ranging from 0 (0 domains impaired) to 3 (.2 domains
impaired). Potential affected neurological domains are motor, sensory, vision, affect, cognition, and language. AHA.SOC-Severity
classifies the severity of the identified neurological domains and has
3 levels: A (no/minimal neurological deficit due to stroke in any
domain), B (mild/moderate deficit due to stroke in $1 domain[s]),
and C (severe deficit due to stroke in $1 domain[s]). AHA.SOCFunction classifies functional disabilities and handicap. This component has 5 levels, ranging from level I (independent in basic
activities of daily living [BADL] and IADL activities and tasks
required of roles patient had before the stroke) to level V (completely
dependent in BADL [$5 areas] and IADL). The Modified Rankin
Scale has 6 levels, ranging from 0 (no disabilities or symptoms) to 5
(severe disability: bedridden and totally dependent).
The OPS18 was used to categorize stroke as minor (1.6#OPS,3.2),
moderate (3.2#OPS#5.2), or major (5.2,OPS#6.8). The Barthel
Index13 measures BADL and is scored on a scale of 0 to 100, with 100
being fully independent in physical functioning. The Lawton IADL,14
which ranges from 9 (completely unable to handle instrumental activities) to 27 (without help), was used to assess higher levels of IADL such
as grocery shopping and use of telephone. The SF-36 includes 8
domains.15 The present study only analyzed 2 of the 8 SF-36 domains
(ie, SF-36 PFI and SF-36 MHI). The SF-36 PFI measures higher level
of physical functioning (eg, vigorous and moderate activities, lifting or
carrying groceries, and walking .1 mile). The SF-36 MHI assesses
mental health dimensions (anxiety, depression, loss of behavioral/
emotional control, and psychological well-being). Scores of both the
SF-36 PFI and the SF-36 MHI range from 0 to 100, with 100 being fully
independent/mentally healthy.
Evaluation of AHA.SOC
1841
Descriptive statistics were used to show demographics, stroke
characteristics, and severity of impairment due to stroke. Since the
majority of scales that were used to assess stroke recovery provide
ordinal level data that are not normally distributed, all analyses in the
present study were performed with the use of nonparametric methods. The concurrent criterion validity of the AHA.SOC was examined by comparing the results from the AHA.SOC with a variety of
measures for impairments, disability, and handicap. The impairment
part of the AHA.SOC was validated by means of Spearman’s
correlation coefficient (rs) by correlating scores of AHA.SOCDomain and AHA.SOC-Severity with stroke severity measured by
the OPS. The concordance between scores of the AHA.SOCFunction and the Modified Rankin Scale was expressed in terms of
relative frequencies and Somers’ D statistic. Correlations between
scores of the AHA.SOC and Modified Rankin Scale and scores of
the Barthel Index, Lawton IADL, SF-36 PFI, and SF-36 MHI were
calculated with the use of Spearman’s rank correlation coefficient.
Kruskal-Wallis tests were used to examine differences in median
scores of Barthel Index, Lawton IADL, SF-36 PFI, and SF-36 MHI
between patients, with levels of disability and handicap measured by
the AHA.SOC and the Modified Rankin Scale.
Results
One hundred five patients were included in this study. The mean
age was 71 (611.2) years at the time of stroke onset. Forty-five
subjects (43%) were male. Eighty-three patients (79%) were
white, 20 (19%) were black, 1 was Hispanic, and 1 was Asian.
Of these 105 patients, ischemic stroke was diagnosed in 99
patients (94%) and intracerebral hemorrhage in 6 patients (6%).
The severity of stroke in these 105 patients was minor in 35
patients (33%), moderate in 63 patients (60%), and severe in 7
subjects (7%). By the end of the 6 months, 8 patients died, 10
refused, and 5 moved out of the study area.
Table 1 shows the relationship between stroke severity
characterized by the OPS and baseline impairment, disability,
and handicap measured by AHA.SOC and the Modified
Rankin Scale. All 7 patients (100%) who had severe stroke
had .2 domains with neurological impairment, while 44 of
the 63 patients (70%) with moderate stroke and 13 of the 35
patients (37%) with minor stroke had .2 domains with
neurological impairment (Table 1). The association was
found to be statistically significant between the number of
neurological domains impaired and stroke severity (rs50.36;
P,0.001). Similarly, all 7 patients with severe stroke had
severe neurological impairment in $1 domain(s), whereas 37
of the 63 moderate strokes (59%) and 3 of the 35 minor
strokes (9%) had severe neurological impairment in $1
domain(s) (Table 1). The correlation coefficient was 0.55,
which was statistically significant (P,0.001). AHA.SOC
classification of disability/handicap was also significantly
associated with stroke severity (rs50.67; P,0.001). Modified
Rankin classifications also differed across minor, moderate,
and major strokes (rs50.65; P,0.001).
The Spearman correlation between the baseline AHA.SOCFunction and the baseline Modified Rankin Scale was found to
be 0.70 (P,0.001). Since none of the 105 patients had a Rankin
score of 0 (ie, no symptoms) at baseline, scores of the
AHA.SOC-Function and the Modified Rankin Scale were further analyzed with the use of Somers’ D statistic (Table 2). The
Somers’ D statistic of 0.65 (P50.035) confirmed the mutual
agreement of these 2 measures of disabilities and handicap.
1842
Stroke
September 1999
TABLE 1. Baseline Characteristics of the Study
Participants (n5105)
Total
(n5105)
Minor
Stroke
(n535)
Moderate
Stroke
(n563)
Severe
Stroke
(n57)
zzz
9 (26%)
zzz
3 (5%)
zzz
1
zzz
12 (11%)
2
28 (27%)
12 (34%)
16 (25%)
3
64 (61%)
13 (37%)
44 (70%)
Baseline
n
Barthel
Lawton
IADL
SF-36 PFI
SF-36 MHI
I
3
100
26
50
88
zzz
II
18
98
22
55
74
zzz
7 (100%)
III
24
78
18
38
64
AHA.SOC-Domain
AHA.SOC-Function
0
AHA.SOC-Severity
A
2 (2%)
1 (3%)
1 (2%)
zzz
B
56 (53%)
31 (89%)
25 (39%)
C
47 (45%)
3 (9%)
37 (59%)
zzz
7 (100%)
AHA-SOC-Function
I
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zzz
3 (3%)
II
III
zzz
2 (6%)
21 (20%)
zzz
1 (2%)
17 (49%)
4 (6%)
zzz
zzz
zzz
IV
38 (36%)
16 (46%)
22 (35%)
V
43 (41%)
zzz
36 (57%)
zzz
7 (100%)
0
zzz
zzz
zzz
zzz
1
zzz
8 (8%)
zzz
7 (20%)
zzz
1 (2%)
zzz
2
3
24 (23%)
17 (49%)
7 (11%)
4
56 (53%)
11 (31%)
44 (70%)
Modified Rankin Scale
5
17 (16%)
11 (17%)
zzz
See text for explanation of classification categories.
zzz
zzz
1 (14%)
6 (86%)
Median 1-month scores of the Barthel Index, Lawton
IADL, SF-36 PFI, and SF-36 MHI are shown in Table 3. The
correlations between the AHA.SOC-Function classification
and 1-month scores of the Barthel Index, Lawton IADL,
SF-36 PFI, and SF-36 MHI were 20.87 (P,0.001), 20.85
(P,0.001), 20.70 (P,0.001), and 20.12 (P50.25), respectively. Similarly, the correlations between the Modified
Rankin Scale and 1-month scores of the Barthel Index,
Lawton IADL, SF-36 PFI, and SF-36 MHI were 20.89
(P,0.001), 20.81 (P,0.001), 20.70 (P,0.001), and 20.09
(P50.41), respectively.
Table 4 summarizes x2 values associated with testing the
TABLE 2. Agreement for Degree of Disability/Handicap
Assessed at Enrollment Using the AHA.SOC-Function Subscale
and the Modified Rankin Scale
1
2
3
4
5
2
III
5
IV
1
10
14
V
Total
0
8
24
33
55
14
5
74
V
22
20
11
5
64
1
zzz
4
zzz
100
zzz
25
zzz
60
zzz
86
2
24
98
21
50
72
3
26
75
17
23
66
4
35
40
13
5
76
5
10
3
10
3
60
Modified Rankin
Scale
0
differences in median 1-month, 3-month, and 6-month scores
on the Barthel Index, Lawton IADL, SF-36 PFI, and SF-36
MHI across the levels of AHA.SOC-Function and the Modified Rankin Scale. Median Barthel scores were significantly
different between the 5 levels of AHA.SOC-Function
(x2574; P,0.001) and the 5 levels of Modified Rankin Scale
(x2580; P,0.001). For Lawton IADL, a Kruskal-Wallis
ANOVA also showed highly significant differences in median scores between the levels of AHA.SOC-Function
(x2571; P,0.001) and the levels of Modified Rankin Scale
(x2564; P,0.001). For SF-36 PFI, significant differences in
median score were also observed (x2545, P,0.001 for
AHA.SOC-Function; x2544, P,0.001 for Modified Rankin
Scale). No differences in median score of SF-36 MHI were
found in either AHA.SOC-Function or the Modified Rankin
Scale. Similar results were observed when scores of 3-month
TABLE 4. Relationship of AHA.SOC and Modified Rankin Scale
with Barthel Index, Lawton IADL, and SF-36
x2
Barthel
Index
Lawton IADL
SF-36 PFI
SF-36 MHI
1 mo
74*
71*
45*
7
3 mo
67*
68*
42*
8†
6 mo
58*
63*
37*
3
Total
Modified Rankin Scale
0
1 mo
80*
64*
44*
6
1
3
3 mo
65*
59*
49*
15†
6
21
6 mo
58*
52*
31*
5
I
II
IV
AHA.SOC-Function
Modified Rankin Scale
AHA.SOCFunction
TABLE 3. Median Scores of Barthel Index, Lawton IADL, SF-36
PFI, and SF-36 MHI Measured at 1 Month After Stroke in
Relation to AHA.SOC and Modified Rankin Scale
23
38
26
17
43
56
17
105
There were no cases in the Modified Rankin Scale of 0.
The calculation of x for PFI and MHI at 3 months did not include Rankin
grade 5 or AHA.SOC level 5 because of small numbers; similarly, calculation of
x2 for PFI and MHI at 6 months did not include Rankin grade 5 or Rankin grade
0 also because of small numbers.
*P#0.001; †P#0.05. x2 by Kruskal-Wallis test.
2
Lai and Duncan
and 6-month Barthel Index, Lawton IADL, SF-36 PFI, and
SF-36 MHI were assessed (Table 4).
Discussion
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The AHA.SOC was designed as a classification system to
comprehensively document stroke impairments and disabilities in a single summary stroke score. Its validity of documenting impairment domains and severity was tested in terms
of correlation with stroke severity and level of disability after
stroke. The strong association of AHA.SOC with stroke
severity measured with the OPS and Barthel Index indicates
concurrent validity of impairment assessment (Table 1).
The AHA.SOC-Function and the Modified Rankin Scale are
similar and strongly correlated (Somers’ D50.65; P,0.001).
Both classifications differentiated stroke severity, disabilities in
BADL and IADL, and physical function (Table 4). Neither of
them differentiated mental health status (Table 4). The
AHA.SOC-Function only differs from the Modified Rankin
Scale in that full range of the AHA.SOC-Function is more likely
to be used to demonstrate patients’ level of outcome after stroke
(Table 2). Patients are more likely to be assigned a grade 5 at
baseline (within 14 days of stroke onset), indicating the worst
outcome, when AHA.SOC-Function is used. The assignment of
outcome classification is more likely to be distributed across all
levels of the AHA.SOC-Function than the Modified Rankin
Scale. Fifty-three percent of the patients were assigned grade 4
at baseline by the Modified Rankin Scale, while the same group
of individuals were primarily distributed across 2 functional
levels (from 4 to 5) by AHA.SOC-Function (Table 2).
Our study results are consistent with those reported by de
Hann et al,10 although in their study the Oxford Handicap
Scale (which was modified from the Modified Rankin Scale
by replacing disability with handicap) was used. de Hann et
al10 also noted in their study that IADL was associated with
the Oxford Handicap Scale,12 although the magnitude of
association was weaker than with BADL. Our study results
also supported their findings in the relationship between the
Modified Rankin Scale and disability in IADL (x2580 for
Barthel Index and x2564 for IADL; Table 4). However, we
observed that the ability of AHA.SOC-Function to discriminate disability in IADL did not decline (x2 574 for Barthel
Index and x2571 for IADL; Table 4).
In our study, both the AHA.SOC and the Modified Rankin
Scale were scored after a battery of instrument assessments.
Consistency in scoring of these 2 measures after a battery of
instrument assessment made comparison of these 2 instruments possible. AHA.SOC is a valid stroke outcome classification schema. All 3 domains of the AHA.SOC were able to
capture impairments, disabilities, and handicap after stroke.
The assignment of outcome classification is more likely to be
distributed across all levels of the AHA.SOC-Function than
the Modified Rankin Scale. The AHA.SOC-Function subscale performs equally as well as the Modified Rankin Scale
in assessing disabilities related to BADL. Neither AHA.SOCFunction nor the Modified Rankin Scale captured differences
in mental health after stroke. In everyday clinical practice,
where a limited number of assessments are done, it may be
less likely to obtain a summary score with the use of the
Evaluation of AHA.SOC
1843
AHA.SOC, whereas the Modified Rankin Scale can be easily
obtained. The AHA.SOC, however, can provide a more
comprehensive clinical assessment of impairment, severity,
and handicap when data are available. Finally, very few
severe stroke patients (n57) and patients with very mild
stroke (Rankin 0 to 2; n58) were included in this study, and
therefore the validity of the AHA.SOC classification system
applied to these patients remains to be tested.
Acknowledgments
This study was supported by the Department of Veterans Affairs
Rehabilitative Research and Development (E879RC), Glaxo-Wellcome
Pharmaceuticals, and University of Kansas Claude D. Pepper Older
Americans Independence Center (NIA 5P60AG14635–02). Participating facilities in the greater Kansas City area include Baptist Hospital,
Department of Veterans Affairs Medical Center at Kansas City and
Leavenworth, Liberty Hospital, Medical Center of Independence, MidAmerican Rehabilitation Hospital, Rehabilitation Institute, Research
Medical Center, St Luke’s Hospital, St Joseph Health Center, Trinity
Lutheran Hospital, and University of Kansas Medical Center.
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Evaluation of the American Heart Association Stroke Outcome Classification
Sue-Min Lai and Pamela W. Duncan
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Stroke. 1999;30:1840-1843
doi: 10.1161/01.STR.30.9.1840
Stroke is published by the American Heart Association, 7272 Greenville Avenue, Dallas, TX 75231
Copyright © 1999 American Heart Association, Inc. All rights reserved.
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