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Functional Status Assessment of Patients With COPD
A Systematic Review of Performance-Based Measures and Patient-Reported
Measures
Yang Liu, PhD, Honghe Li, PhD, Ning Ding, PhD, Ningning Wang, PhD, and Deliang Wen, PhD
Abstract: Presently, there is no recommendation on how to assess
functional status of chronic obstructive pulmonary disease (COPD)
patients. This study aimed to summarize and systematically evaluate
these measures.
Studies on measures of COPD patients’ functional status published
before the end of January 2015 were included using a search filters in
PubMed and Web of Science, screening reference lists of all included
studies, and cross-checking against some relevant reviews. After title,
abstract, and main text screening, the remaining was appraised using the
Consensus-based Standards for the Selection of Health Measurement
Instruments (COSMIN) 4-point checklist. All measures from these
studies were rated according to best-evidence synthesis and the best-
rated measures were selected.
A total of 6447 records were found and 102 studies were reviewed,
suggesting 44 performance-based measures and 14 patient-reported
measures. The majority of the studies focused on internal consistency,
reliability, and hypothesis testing, but only 21% of them employed good
or excellent methodology. Their common weaknesses include lack of
checks for unidimensionality,inadequate sample sizes,no prior hypoth-
eses, and improper methods. On average, patient-reported measures
perform better than performance-based measures. The best-rated
patient-reported measures are functional performance inventory
(FPI), functional performance inventory short form (FPI-SF), living
with COPD questionnaire (LCOPD), COPD activity rating scale
(CARS), University of Cincinnati dyspnea questionnaire (UCDQ),
shortness of breath with daily activities (SOBDA), and short-form
pulmonary functional status scale (PFSS-11), and the best-rated per-
formance-based measures are exercise testing: 6-minute walk test
(6MWT), endurance treadmill test, and usual 4-meter gait speed (usual
4MGS).
Further research is needed to evaluate the reliability and validity of
performance-based measures since present studies failed to provide
convincing evidence. FPI, FPI-SF, LCOPD, CARS, UCDQ, SOBDA,
PFSS-11, 6MWT, endurance treadmill test, and usual 4MGS performed
well and are preferable to assess functional status of COPD patients.
(Medicine 95(20):e3672)
Abbreviations: 10MGS = maximal 10-meter gait speed, 10MGS =
usual 10-meter gait speed, 12MD = 12-minute distance walk,
2MWT = 2-minute walk test, 30MWT = 30-meter walk test, 3CRT
= 3-minute chair rise test, 4MGS = 4-meter gait speed, 4MGS = 4-
meter gait speed, 5STS = five-repetition sit-to-stand test, 6MST =
6-minute step test, 6MWT = 6-minute walk test, ADL-D = activity
of daily living dyspnea scale, ADLs = activities of daily living, AH
= actiheart, AUC = area under the curve, CARS = COPD activity
rating scale, CAT = COPD assessment test, CDLM = capacity of
daily living during the morning questionnaire, COPD = chronic
obstructive pulmonary disease, COSMIN = consensus-based
standards for the selection of health measurement instruments,
DAM = DynaPort activity monitor, DASI = Duke activity status
index, DIF = differential item functioning, DIRECT = DIsability
RElated to COPD Tool, ESWT = endurance shuttle walking test,
FPI = functional performance inventory, FPI-SF = functional
performance inventory short form, GST = grocery shelving task,
HRQOL = health-related quality of life, ICC = intraclass
correlation coefficient, ISWT/SWT = incremental shuttle walk
test, LCADL = London chest activity of daily living scale, LCOPD
= living with COPD questionnaire, LoA = limits of agreement,
M6MWT = modified 6-minute walk test, MIC = minimal important
change, MRADL = Manchester respiratory activities of daily living
questionnaire, MSWT = modified SWT, PBRT = 6-minute
pegboard and ring test, PFSDQ-M = pulmonary functional status
and dyspnea questionnaire-modified, PFSS = pulmonary functional
status scale, PFSS-11 = short-form pulmonary functional status
scale, PRO = patient-reported outcomes, PW = power walker 610,
SAB = SenseWear armband, SAM = StepWatch activity monitor,
SCAM = self-contained activity monitor, SCPT = stair climb power
test, SDC = smallest detectable change, SOBDA = shortness of
breath with daily activities, SRAT = steep ramp anaerobic test,
STST = sit-to-stand test, TChester = Chester step test, UCDQ =
University of Cincinnati dyspnea questionnaire, UULEX =
unsupported upper limb exercise test.
INTRODUCTION
Chronic obstructive pulmonary disease (COPD), character-
ized by persistent airflow limitation, is usually progressive
and associated with an enhanced chronic inflammatory
response in the airways and the lung to noxious particles or
gases.
1
When the disease becomes aggravated, patients suffer
from deteriorated functional status and limitations to daily life.
The impaired functional status is proven to be predictors of
exacerbations, hospital admissions, and mortality.
2,3
The wor-
sening functional status presents a tough challenge for patients
and their families and causes an increasing burden for the
Editor: Chengwu Yang.
Received: January 7, 2016; revised: April 5, 2016; accepted: April 15,
2016.
From the School of Public Health (YL, HL, DW); The Research Centre for
Medical Education (ND), China Medical University, Shenyang; and School
of Public Health (NW), Dalian Medical University, Dalian, Liaoning,
China.
Correspondence: Deliang Wen, China Medical University, No. 77 Puhe
Road, Shenyang North New Area, Shenyang, Liaoning Province,
People’s Republic of China (e-mail: dlwen@cmu.edu.cn).
This study was supported by Natural Science Foundation of China (NSFC)
(fund number: 71573032).
The authors have no conflicts of interest to disclose.
Supplemental Digital Content is available for this article.
Copyright #2016 Wolters Kluwer Health, Inc. All rights reserved.
This is an open access article distributed under the Creative Commons
Attribution-NoDerivatives License 4.0, which allows for redistribution,
commercial and non-commercial, as long as it is passed along unchanged
and in whole, with credit to the author.
ISSN: 0025-7974
DOI: 10.1097/MD.0000000000003672
Medicine®
SYSTEMATIC REVIEW AND META-ANALYSIS
Medicine Volume 95, Number 20, May 2016 www.md-journal.com |1
society.
4
Therefore, assessing functional status accurately and
systemically is one of demanding require of COPD treatments,
as indicated in COPD guidelines.
1,5,6
Measuring the typeand magnitude of functional damageand
evaluating treatment effect on functional improvement is a
challenging work in clinical practice. Even in some large pul-
monary rehabilitation programs, variables like activities of daily
living (ADLs) and exercise tolerance were not adequately
assessed.
7,8
Functional status contains multidimensional con-
structs and is often confused with other relevant constructs.
9–
13
According to the Wilson-Cleary framework, functional status
was broadly defined as the ability to perform particular defined
tasks in multiple domains, including physical function, social
function, role function, and psychological function.
14,15
Sim-
ilarly, there are also many aspects of functional status in terms
of intension, including functional capacity, functional perform-
ance, functional reserve, and functional capacity utilization.
Correspondingly, many functional status instruments were pro-
posed for different purposes, including performance-based
measures and patient-reported measures.
12,16–19
Two limitations
in present studies, undermining the development and validation
of these instruments,are (1) lack of an assessment of the quality of
methodology used, resulting in unconvincing conclusions of
measures’ development and/or validation; (2) lack of a clear-
defined, systematical, and quantifiable assessment standard,
resulting in partial and ambiguous judgments on measures per-
formance.
20– 22
Consensus-based standards for the selection of health
measurement instruments (COSMIN) was proposed in
2006.
20– 23
Besides evaluating the quality of studies on measure-
ment property critically, COSMIN also includes the measure-
ment properties systematically. It has been used in many
systematic reviews to evaluate studies and instruments of
various diseases, such as hip and knee osteoarthritis, geriatrics,
non-small cell lung carcinoma, and neuro-rehabilitation
patients.
24– 27
In terms of COPD, COSMIN has been used to
assess COPD assessment test (CAT) questionnaire, health-
related quality of life (HRQOL) questionnaires, and arm exer-
cise capacity.
28– 30
In this article, we employed COSMIN to
review both patient-reported measures and performance-based
measures of COPD patients’ functional status.
The objectives of this review is threefold: (1) to appraise
the quality of methodology in the studies on the measures of
COPD patients’ functional status and to provide insights for
future researches, (2) to summarize all candidate instruments
and to make recommendations for instrument selection, and (3)
to compare performance-based measures and patients-reported
measures.
METHOD
Search Strategy
We searched PubMed, Web of Science using a search filter
developed by Terwee to identify studies describing develop-
ment or evaluation of measurement properties of instruments
measuring functional status of COPD patients up to the end of
January 2015. (See text, Supplemental Digital Content 1, http://
links.lww.com/MD/A969, which describes the detailed search
strategy.)
31
1# Construct search
2# Population search
3# Instrument search
4# #1 AND #2 AND #3 AND filter for measurement
properties
5# #4 NOT exclusion filter
For supplement, we searched each instrument in the entire
database and looked up the references of each included article.
Finally, our review was cross-checked against some relevant
reviews.
16,17,19,24
Eligibility Criteria and Study Selection
By applying the inclusion and exclusion criteria (Table 1),
3 reviewers (YL, HL, and ND) independently screened titles
and abstracts of the identified records and independently
assessed full texts for eligibility. Discussion was conducted
when there were differences concerning exclusion criteria. If
consensus could not be reached, the final decision was made by
the forth reviewer (NW).
Evaluation of Methodological Quality of the
Included Studies
Before the evaluation of methodological quality of the
included studies, descriptive variables of these studies including
authors/year, country, study sample, study design, sex (female,
%), mean age years SD (range), mean percentage of the
TABLE 1. Inclusion Criteria and Exclusion Criteria for Eligible Studies
Criteria Inclusion Exclusion
Criteria 1: Population COPD patients All others
Criteria 2: Content Studies described the development
or evaluation of the
measurement properties or
studies that reported at least one
or more psychometric properties
were included
Studies where the objective was the evaluation of an
intervention or treatment without reporting any
measurement properties were excluded. Studies in which
the measurement instruments were used as an end point
without studying the measurement properties were not
considered eligible
Criteria 3: Instrument Studies of instruments measuring
functional status were included
Studies of instruments measuring HRQOL, general health
perception, or only symptoms or satisfaction with care and
adherence were excluded
Criteria 4: Characters of literature English; full text; original article Other languages; conference papers; editorials;
commentaries; supplementary
Criteria 5: Journal Peer-reviewed All others
COPD ¼chronic obstructive pulmonary disease, HRQOL ¼health-related quality of life.
Liu et al Medicine Volume 95, Number 20, May 2016
2|www.md-journal.com Copyright #2016 Wolters Kluwer Health, Inc. All rights reserved.
forced vital capacity (FEV1%) predicted SD, and patients
status were collected. Then the methodological quality of
included studies was evaluated according to the COSMIN 4-
point checklist.
32
The COSMIN checklist consists of 9 boxes
concerning methodological standards on how each measure-
ment property should be assessed, including 5 to 18 items in
each box. The overall score (i.e., poor, fair, good, or excellent)
for each item was obtained by taking the lowest score for any
question within the item.
Quality Assessment of Instruments
The quality of the instruments was determined according
to the rating system provided by Terwee (Table 2). It contains
criteria for content validity, internal consistency, criterion
validity, construct validity, reproducibility (agreement and
reliability), responsiveness, floor and ceiling effects, and inter-
pretability. Each measurement property was reported by
positive (þ), intermediate (?), negative (–), or no information
available (0). The version provided by Terwee was used in
this review.
Data Synthesis and Quality Assessment
To synthesize the evidence, ‘‘best-evidence synthesis’’ was
performed. As proposed by the Cochrane Back Review Group,
the levels of evidence were ‘‘strong,’’ ‘‘‘‘moderate,’’ ‘‘limited,’’
‘‘conflicting,’’ or ‘‘unknown’’ (Table 3).
33,34
Methodological
quality of the studies (COSMIN score), rating of quality assess-
ment of instruments, consistency between different studies, and
the number of studies were taken into consideration using the
synthesis. We defined best rated instruments as those which had a
‘‘þþþ’’ (strong positive) in at least one measurement property
or a ‘‘þ’’ or ‘‘þþ’’ in at least three measurement properties
according to the results of data synthesis.
Since this study merely reviewed the articles already
published without involving any human participants directly,
ethical approval is not necessary.
RESULTS
Electronic Literature Search Results
The selection process for all studies is shown in Figure 1.
With the search filter, 6447 records were identified. After
screening the title and abstract, 6225 records were excluded.
The remaining 222 records were screened for full text, among
which 145 records were excluded for various reasons shown in
Figure 1. Twenty-five additional records were identified
through screening of references lists and review articles and
searching for each particular instrument in PubMed. A total of
102 articles were analyzed in the review.
Description of the Included Studies and Included
Instruments
A total of 95 of the 102 studies were published after 2000.
These included cross-sectional studies, longitudinal studies, and
randomized double-blind studies. Mean age of subjects include
in these studies ranged from 51.0 to 74.7 years. Fifty of the 102
studies declared that subjects include in their studies were stable
patients. In total, 58 instruments were identified, including 44
performance-based measures and 14 patient-reported measures.
The 44 performance-based measures could be divided into 28
exercise tests and 16 activity monitors. (See table, Supplemental
Digital Content 2, http://links.lww.com/MD/A969, which
describes the included studies.)
Quality of the Included Studies
The quality of included studies can be found in
Tables 4 and 5. The methodological quality of the existing
studies ranged from poor to excellent, with good and excellent
collectively taking 21%.
Studies on performance-based measures
There were 89 studies that analyzed the measurement
properties of performance-based measures. Reliability and hy-
pothesis testing were the most reported measurement properties
of this type of instrument (reported in 52 studies and 35 studies,
respectively). Criterion validity and responsiveness were
reported in 20 studies and 24 studies, respectively. Unlike
the patient-reported measures, performance-based measures
had some evidence of measurement error from 7 studies.
Of the studies reporting on reliability, 2 were excellent,12
were good, 12 were fair, and 26 were poor. Inadequate sample
size and no intraclass correlation coefficient (ICC) or Pearson
or Spearman correlations calculated were the main reasons
contributing to poor quality of the study. For hypothesis testing,
2 studies were good,16fair, and 17 poor. The main weakness
lies in inadequate sample sizes and a lack of adequate hypoth-
eses. Evaluating the criterion validity, most studies chose the
direct observation as the gold criterion. However, 12 studies
were considered poor in criterion validity because of inadequate
sample sizes. Among the 20 studies reporting responsiveness,1
study had good quality, 7 studies had fair quality, and 16 studies
had poor quality.
Studies on patient-reported measures
Among the 32 studies analyzing the measurement proper-
ties of patient-reported measures, internal consistency,
reliability, and hypothesis testing were the measurement proper-
ties reported most frequently (reported in 21, 20, and 21 studies,
respectively), whereas no study reported on the measurement
error of the patient-reported measures. Cross-cultural validity
and criterion validity were also only reported in 6 studies and 2
studies, respectively. Content validity and cross-cultural
validity were more so evaluated in the development of the
scales rather than in the final version.
The qualities of the studies analyzing the internal consist-
ency of patients-reported measures were as follows: 1 excellent,
3good,4fair, and 13 poor. Studies were deemed poor mostly
because of the fact that unidimensionality was not properly
checked. The quality of the studies analyzing the reliability was
1excellent,5good,9fair, and 5 poor. Inadequate sample size
was the decisive factor of lesser quality. The quality of the
studies analyzing the hypothesis testing was 4 good and 17 fair.
The quality of most studies stopped at fair because of that they
did not formulate any hypotheses in their studies. Studies
reporting responsiveness did not have high quality because
of inadequate sample sizes or to the fact that inappropriate
methods were used. Structural validity was analyzed in 8 studies
and the qualities were mostly determined by the sample
size.
111,113– 115,119,124– 126
Quality of Psychometric Properties for Outcome
Measures
A summary of best-evidence synthesis is provided in
Table 6. The summary was driven from the results of
study qualities and the quality of psychometric properties for
outcome measures (see table, Supplemental Digital Content 3,
http://links.lww.com/MD/A969, which describes quality of
Medicine Volume 95, Number 20, May 2016 Functional Status Assessment in Patients With COPD
Copyright #2016 Wolters Kluwer Health, Inc. All rights reserved. www.md-journal.com |3
TABLE 2. Quality Criteria for Measurement Properties
7
Property Rating Quality Criteria
Reliability
Internal consistency
þCronbach’s alpha (s) 0.70
? Cronbach’s alpha not determined or dimensionality unknown
– Cronbach’s alpha (s) <0.70
Reliability
þICC/weighted Kappa 0.70 OR Pearson r0.80
? Neither ICC/weighted Kappa, nor Pearson rdetermined
– ICC/weighted Kappa <0.70 OR Pearson r<0.80
Measurement error
þMIC >SDC OR MIC outside the LoA
? MIC not defined
– MIC SDC OR MIC equals or inside LoA
Validity
Content validity
þAll items are considered to be relevant for the construct to be measured, for the target
population, and for the purpose of the measurement AND the questionnaire is
considered to be comprehensive
? Not enough information available
– Not all items are considered to be relevant for the construct to be measured, for the
target population, and for the purpose of the measurement OR the questionnaire is
considered not to be comprehensive
Construct validity–Structural validity
þFactors should explain at least 50% of the variance
? Explained variance not mentioned
– Factors explain <50% of the variance
- Hypothesis testing
þCorrelations with instruments measuring the same construct 0.50 OR at least 75% of
the results are in accordance with the hypotheses AND correlations with related
constructs are higher than with unrelated constructs
? Solely correlations determined with unrelated constructs
– Correlations with instruments measuring the same construct <0.50 OR <75% of the
results are in accordance with the hypotheses OR correlations with related
constructs are lower than with unrelated constructs
- Cross-cultural validity
þNo differences in factor structure OR no important DIF between language versions
? Multiple group factor analysis not applied AND DIF not assessed
– Differences in factor structure OR important DIF between language versions
Criterion validity
þConvincing arguments that gold standard is ‘‘gold’’ AND correlation with gold
standard 0.70
? No convincing arguments that gold standard is ‘‘gold’’
– Correlation with gold standard <0.70
Responsiveness
Responsiveness
þCorrelation with changes on instruments measuring the same construct 0.50 OR at
least 75% of the results are in accordance with the hypotheses OR AUC 0.70 AND
correlations with changes in related constructs are higher than with unrelated
constructs
? Solely correlations determined with unrelated constructs
– Correlations with changes on instruments measuring the same construct <0.50 OR
<75% of the results are in accordance with the hypotheses OR AUC <0.70 OR
correlations with changes in related constructs are lower than with unrelated
constructs
?¼indeterminate rating, þ¼positive rating, – ¼negative rating, AUC ¼area under the curve, DIF ¼differential item functioning,
ICC ¼intraclass correlation coefficient, LoA ¼limits of agreement, MIC ¼minimal important change, SDC ¼smallest detectable change.
Liu et al Medicine Volume 95, Number 20, May 2016
4|www.md-journal.com Copyright #2016 Wolters Kluwer Health, Inc. All rights reserved.
psychometric properties for outcome measures) using the
criteria displayed in Table 3.
Patient-reported measures performed better than perform-
ance-based measures. All positive evidence of patient-reported
measures were evenly distributed in both reliability and
validity. Most of the positive evidence of performance-based
measures was confined to exercise testing and reliability
measurement property.
Best rated instruments with a ‘‘þþþ’’ in one measure-
ment property or ‘‘þ’’/‘‘þþ’’ in at least three measurement
properties among performance-based measures are 6-minute
walk test (6MWT), endurance treadmill test, and usual 4-meter
gait speed (usual 4MGS). The best rated patients-reported
measures were functional performance inventory (FPI), func-
tional performance inventory short form (FPI-SF), living with
COPD questionnaire (LCOPD), COPD activity rating scale
(CARS), University of Cincinnati dyspnea questionnaire
(UCDQ), shortness of breath with daily activities (SOBDA),
and short-form pulmonary functional status scale (PFSS-11).
DISCUSSION
The present review provides the first evidence on compar-
ing all candidate instruments measuring functional status in
COPD patients according to the COSMIN criteria. It high-
lighted some areas worthy of future researched, including the
lack of adequate positive evidence on measurement properties
of performance-based measures compared with patient-reported
measures, the weakness limiting the quality of the existing
studies, and the important measurement properties neglected by
existing studies. Although none of the instruments was tested
for all measurement properties, the existing evidence still
confirms that some instruments performed better in terms of
some measurement properties or some survey types. For clinical
TABLE 3. Levels of Evidence for the Quality of the Measure-
ment Property
34
Level Rating Criteria
Strong þþþ or – – – Consistent findings in multiple
studies of good;
methodological quality OR in
one study of excellent;
methodological quality
Moderate þþ or – – Consistent findings in multiple
studies of fair;
methodological quality OR in
one study of good;
methodological quality
Limited þor – One study of fair
methodological quality
Conflicting Conflicting findings
Unknown ? Only studies of poor
methodological quality
–¼negative rating, OR ¼,þ¼positive rating, ? ¼indeterminate
rating.
FIGURE 1. Flow diagram of search results.
Medicine Volume 95, Number 20, May 2016 Functional Status Assessment in Patients With COPD
Copyright #2016 Wolters Kluwer Health, Inc. All rights reserved. www.md-journal.com |5
TABLE 4. Results of Quality of Design, Methods, and Reporting for Included Studies on Performance-Based Measures
Psychometric Properties
Authors/Year
Box A
Internal
Consistency
Box B
Reliability
Box C
Measurement
Error
Box D
Content
Validity
Box E
Structural
Validity
Box F
Hypothesis
Testing
Box G
Cross-Cultural
Validity
Box H
Criterion
Validity
Box I
Responsiveness
2MWT
Butland et al/1982
35
Poor (3,11) Poor (7,8)
Eiser et al/2003
36
Poor (11) Poor (14)
Leung et al/2006
37
Fair (3,6,8) Fair (3,4,8) Poor (3)
6MWT
Eiser et al/2003
36
Poor (11) Poor (14)
Casanova et al/2007
38
Poor (8,11,12,13,14)
Brown et al/2008
39
Fair (40)
Spencer et al/2008
40
Fair (3,8,14)
Jenkins and Cecins/
2010
41
Poor (11)
Chatterjee et al/2010
42
Good (3)
Hernandes et al/2011
44
Excellent
Andersson et al/2011
43
Fair (3)
Puhan et al/2011
45
Fair (8)
Chandra et al/2012
46
Fair (11,12)
M6MWT
Burioka et al/2014
47
Poor (3)
12MD
Mungall and
Hainsworth/1979
48
Poor (3,11) Poor (3,7,8)
Larson et al/1996
49
Fair (3,8,11) Fair (4)
6MST
Borel et al/2010
50
Poor (3,8,11) Poor (3)
Marrara et al/2012
51
Poor
da Costa et al/2014
52
Fair (3,8) Poor (11,12,13)
Pessoa et al/2014
53
Fair (3,4)
Coquart et al/2015
54
Fair (3) Fair (3)
30MWT
Andersson et al/2011
43
Fair (3) Fair (3) Fair (3,4)
ISWT/SWT
Singh et al/1992
55
Poor (3) Poor (3)
Singh et al/1994
56
Poor (3,4)
Eiser et al/2003
36
Poor (11) Poor (14)
Rosa et al/2006
57
Poor (3)
Perrault et al/2009
58
Fair (3)
McKeough et al/2011
59
Poor (11) Poor (13)
ESWT
Revill et al/1999
60
Poor (3,11) Poor (3,13)
Liu et al Medicine Volume 95, Number 20, May 2016
6|www.md-journal.com Copyright #2016 Wolters Kluwer Health, Inc. All rights reserved.
Psychometric Properties
Authors/Year
Box A
Internal
Consistency
Box B
Reliability
Box C
Measurement
Error
Box D
Content
Validity
Box E
Structural
Validity
Box F
Hypothesis
Testing
Box G
Cross-Cultural
Validity
Box H
Criterion
Validity
Box I
Responsiveness
Brouillard et al/2008
61
Poor (3,13)
Revill et al/2009
62
Poor (11)
McKeough et al/2011
59
Poor (11) Poor (13)
Borel et al/2014
63
Good (7) Fair (12)
MSWT
Campo et al/2006
64
Fair (3) Fair (3)
Usual and fast walking speeds
Rozenberg et al/2014
65
Poor (3) Poor (3)
Incremental treadmill
test
Mathur et al/1995
66
Poor (3,11)
Endurance treadmill
test
Cooper et al/2010
67
Excellent
Incremental cycle ergometer test
Mathur et al/1995
66
Poor (3,11)
Covey et al/1999
68
Good (3)
Cox et al/1989
69
Poor (3,11)
Brown et al/2008
39
Fair (4)
Puhan et al/2011
45
Fair (8)
Endurance cycle ergometer test
van’t Hul et al/2010
70
Good (3) Fair (3,4)
UULEX
Takahashi et al/2003
71
Poor (3) Poor (3)
Janaudis-Ferreira et al/
2013
72
Fair (3) Poor (6)
PBRT
Zhan et al/2006
73
Poor (3) Poor (3)
Janaudis-Ferreira et al/
2013
72
Fair (3) Poor (6)
Semipaced 3CRT
Aguilaniu et al/2014
74
Fair (3) Fair (3,9,10)
STST
Ozalevli et al/2007
75
Fair (4)
5STS
Jones et al/2013
76
Good (3) Good (1,7,8) Good (12)
Usual 4MGS
Kon et al/2014
77
Good (3) Good (3) Fair (4,7,8)
Kon et al/2013
78
Fair (11,12)
Karpman et al/2014
79
Good (1,3) Good (1,3)
Maximal 4MGS
Medicine Volume 95, Number 20, May 2016 Functional Status Assessment in Patients With COPD
Copyright #2016 Wolters Kluwer Health, Inc. All rights reserved. www.md-journal.com |7
Psychometric Properties
Authors/Year
Box A
Internal
Consistency
Box B
Reliability
Box C
Measurement
Error
Box D
Content
Validity
Box E
Structural
Validity
Box F
Hypothesis
Testing
Box G
Cross-Cultural
Validity
Box H
Criterion
Validity
Box I
Responsiveness
Karpman et al/2014
79
Good (1,3) Good (1,3)
Usual 10MGS
Karpman et al/2014
79
Good (1,3) Good (1,3)
Maximal 10MGS
Karpman et al/2014
79
Good (1,3) Good (1,3)
GST
Hill et al/2008
80
Poor (3,11) Poor (3) Fair (3,8)
TChester
Karloh et al/2013
81
Poor (3)
de Camargo et al/
2011
82
Fair (3) Fair (3,4,8)
SRAT
Chura et al/2012
83
Poor (3)
SCPT
Roig et al/2010
84
Poor (3) Poor (3)
Glittre ADL-test
Skumlien et al/2006
85
Good (3) Fair (4,8,9) Fair (3,12,13,14)
Correˆa et al/2011
86
Poor (3)
Karloh et al/2014
87
Poor (3)
PW 610
Sant’Anna et al/2012
88
Fair (3) Fair (3,4)
SAB
Farooqi et al/2013
89
Poor (3)
Patel et al/2007
90
Poor (3) Poor (3)
Waschki et al/2012
91
Fair (4,7,8,9,10)
Watz et al/2009
92
Good (11) Fair (4,7,8)
Cavalheri et al/2011
93
Poor (6)
Hill et al/2010
94
Poor (3,11) Poor (3,6)
Rabinovich et al/
2013
95
Good (3)
Andersson et al/2014
96
Poor (3,6)
DAM
Kanda et al/2012
97
Poor (3)
Pitta et al/2005
98
Poor (3)
Rabinovich et al/
2013
95
Good (3)
Andersson et al/2014
96
Poor (3,6)
Lifecorder PLUS (Kenz Suzuken Co Ltd, Nagoya, Japan)
Rabinovich et al/
2013
95
Good (3)
Actiwatch Spectrum (Philips Respironics, Bend, OR)
Liu et al Medicine Volume 95, Number 20, May 2016
8|www.md-journal.com Copyright #2016 Wolters Kluwer Health, Inc. All rights reserved.
Psychometric Properties
Authors/Year
Box A
Internal
Consistency
Box B
Reliability
Box C
Measurement
Error
Box D
Content
Validity
Box E
Structural
Validity
Box F
Hypothesis
Testing
Box G
Cross-Cultural
Validity
Box H
Criterion
Validity
Box I
Responsiveness
Rabinovich et al/
2013
95
Good (3)
Actimarker
Sugino et al/2012
99
Poor (3) Poor (3)
AH
Farooqi et al/2013
89
Poor (3)
SAM
Cindy et al/2012
100
Poor (3,6) Poor (3,4)
Moy et al/2012
101
Fair (4,10) Poor (5,6)
ActivPAL
Cindy et al/2012
100
Poor (3,6) Poor (3,4)
SCAM
Coronado et al/2003
102
Poor (3,13,14)
RT3 (StayHealthy, Inc., Monrovia, CA )
Rabinovich et al/
2013
95
Good (3)
Actigraph GT3X:
Actigraph LLC,
Pensacola, FL
Rabinovich et al/
2013
95
Good (3)
Pedometer: Fitty 3
(Kasper & Richter
Company,
Uttenreuth,
Germany)
Scho¨nhofer et al/
1997
103
Poor (3)
Tritrac R3D
accelerometer
Steele et al/2000
104
Fair (3) Fair (3,4,8)
Three-axis accelerometers: Fitbit Ultra (Fitbit Inc., San Francisco)
Vooijs et al/2014
105
Poor (3)
Three-axis accelerometers: Personal Activity Monitor AM300 (PAM BV Doorwerth, the Netherlands)
Vooijs et al/2014
105
Poor (3)
The numbers in () correspond to the item in each COSMIN box of which the assessment is based on.
10MGS ¼10-meter gait speed, 10MGS ¼10-meter gait speed, 12MD ¼12-minute distance walk, 2MWT ¼2-minute walk test, 30MWT ¼30-meter walk test, 3CRT ¼3-minute chair rise test,
4MGS ¼4-meter gait speed, 5STS ¼five-repetition sit-to-stand test, 6MST ¼6-minute step test, 6MWT ¼6-minute walk test, ADL ¼activity of daily living, AH ¼ActiHeart, DAM ¼DynaPort activity
monitor, ESWT ¼endurance shuttle walking test, GST ¼grocery shelving task, ISWT/SWT ¼incremental shuttle walk test, M6MWT ¼modified 6-minute walk test, MSWT ¼modified SWT,
PBRT ¼6-minute pegboard and ring test, PW ¼power walker, SAB ¼SenseWear armband, SAM¼StepWatch
TM
activity monitor, SCAM ¼self-contained activity monitor, SCPT ¼stair climb power
test, SRAT ¼steep ramp anaerobic test, STST ¼sit-to-stand test, TChester ¼Chester step test, UULEX ¼unsupported upper limb exercise test.
Medicine Volume 95, Number 20, May 2016 Functional Status Assessment in Patients With COPD
Copyright #2016 Wolters Kluwer Health, Inc. All rights reserved. www.md-journal.com |9
TABLE 5. Results of Quality of Design, Methods, and Reporting for Included Studies on Patient-Reported Measures
Psychometric Properties
Authors/Year
Box A
Internal
Consistency
Box B
Reliability
Box C
Measurement
Error
Box D
Content
Validity
Box E
Structural
Validity
Box F
Hypothesis
Testing
Box G
Cross-Cultural
Validity
Box H
Criterion
Validity
Box I
Responsiveness
LCADL
Garrod/2000
106
Poor (6,7) Fair (2,4)
Garrod/2002
107
Poor (3)
Fair (11,12)
Carpes/2008
108
Fair (2,3)
Fair (2,3,8)
Kovelis et al/2011
109
Poor (3)
FPI
Larson et al/1998
110
Poor (5,6) Fair (4)
Leidy/1999
111
Poor (6)
Good (3,7,9)
Good (3) Good (2)
Weldam et al/2015
112
Poor (5,6)
Good (1,2,3)
Good (1,2,3)
Ozkan et al/2009
113
FPI-SF
Leidy and Knebel/2010
114
Poor (6)
Good (3,7,9)
Good (3) Good (2)
Guo et al/2011
115
Poor (5,6)
Fair (3)
Fair (4,8) Poor (3,14)
Leidy et al/2012
116
Good (3)
Wall/2007
117
Poor (5) Good (1,2,4,6)
LCOPD
Stephen/2011
118
Good (1,6)
Fair (11)for
UK; Fair
(3,11)
for USA
Good (3) Good (2) Fair (4,7,8)
Stephen/2012
119
Fair (5)
Fair (11)
Fair (1,3,4,7,8) Poor (14)
CARS
Morimoto et al/2003
120
Fair (3) Poor (5) Fair (3) Fair (2,4,8)
UCDQ
Lee et al/1998
121
Fair (8) Fair (5)
Hodgev et al/2003
122
Poor (6)
Poor (3)
Poor (4) Fair (2,4,7,8)
Binazzi et al/2010
123
Poor (3)
ADL-D scale
Yoza et al/2009
124
Poor (5,) Fair (2,4,7,8)
DIRECT
Liu et al Medicine Volume 95, Number 20, May 2016
10 |www.md-journal.com Copyright #2016 Wolters Kluwer Health, Inc. All rights reserved.
Psychometric Properties
Authors/Year
Box A
Internal
Consistency
Box B
Reliability
Box C
Measurement
Error
Box D
Content
Validity
Box E
Structural
Validity
Box F
Hypothesis
Testing
Box G
Cross-Cultural
Validity
Box H
Criterion
Validity
Box I
Responsiveness
Aguilaniu et al/2011
125
Good (3) Fair (8)
SOBDA
Wilcox et al/2013
126
Excellent
Excellent
Excellent Fair (4,7,8)
Watkins et al/2013
127
Poor (5)
Fair (8)
Fair (4,7,8) Fair (8,11,12,13,14)
CDLM
Partridge et al/2010
128
Poor (5)
Fair (5,8)
Fair (4,7,8) Fair (14)
PFSDQ-M
Winga
˚rdh et al/2007
129
Fair (3)
Kovelis et al/2008
130
Poor (5)
Fair (3,8,10)
Poor (4)
Lareau et al/1998
131
Poor (5)
Fair (2,3,10)
Poor (4) Poor (4)
Kovelis et al/2011
109
Poor (3)
PFSS
Weaver et al/1998
132
Fair (8)
Poor (3)
Poor (2) fair (5) Fair (4,7,8)
PFSS-11
Chen et al/2010
133
Good (1)
Poor
Good (1) Fair (2,9) Fair (13,14)
DASI
Tavares et al/2012
134
Good (3)
Fair (4)
Carter et al/2002
135
Fair (4) Good (1,4)
MRADL
Yohannes et al/2002
136
Good (3)
(mail) Fair (3)
(face to face)
The numbers in () correspond to the item in each COSMIN box of which the assessment is based on.
ADL-D ¼activity of daily living dyspnea scale, CARS ¼COPD activity rating scale, CDLM ¼capacity of daily living during the morning questionnaire, DASI ¼Duke activity status index,
DIRECT ¼disability related to COPD tool, FPI ¼functional performance inventory, FPI-SF ¼functional performance inventory short form, LCADL ¼London chest activity of daily living scale,
LCOPD ¼living with COPD questionnaire, MRADL ¼Manchester respiratory activities of daily living questionnaire, PFSDQ-M ¼pulmonary functional status & dyspnea questionnaire-modified,
PFSS ¼pulmonary functional status scale, PFSS-11 ¼short-form pulmonary functional status scale, SOBDA ¼shortness of breath with daily activities, UCDQ ¼University of Cincinnati dyspnea
questionnaire.
Medicine Volume 95, Number 20, May 2016 Functional Status Assessment in Patients With COPD
Copyright #2016 Wolters Kluwer Health, Inc. All rights reserved. www.md-journal.com |11
TABLE 6. A Summary of Best-Evidence Synthesis
Category Instrument
Box A
Internal
Consistency
Box B
Reliability
Box C
Measurement
Error
Box D
Content
Validity
Box E
Structural
Validity
Box F
Hypothesis
Testing
Box G
Cross-Cultural
Validity
Box H
Criterion
Validity
Box I
Responsiveness
Exercise testing 2MWT þþ?
Exercise testing 6MWT þþþ þ
Exercise testing M6MWT ?
Exercise testing 12MD þþ –
Exercise testing 6MST þþ ??þ?
Exercise testing 30MWT þ?þ
Exercise testing ISWT/SWT þ??
Exercise testing ESWT þþ þ
Exercise testing MSWT þ þ
Exercise testing Usual and fast
walking speeds
??
Exercise testing Incremental
treadmill test
þþ
Exercise testing Endurance treadmill
test
þþþ
Exercise testing Incremental cycle
ergometer test
? ?
Exercise testing Endurance cycle
ergometer test
þþ
Exercise testing UULEX ? þ?
Exercise testing PBRT ? þ?
Exercise testing Semipaced 3CRT þ?
Exercise testing STST þ
Exercise testing 5STS þþ þþ ––
Exercise testing Usual 4MGS þþþ ?þ–
Exercise testing Maximal 4MGS þþ ?
Exercise testing Usual 10MGS þþ ?
Exercise testing Maximal 10MGS þþ ?
Exercise testing GST ? ? –
Exercise testing TChester þþ
Exercise testing SRAT ?
Exercise testing SCPT ? ?
Exercise testing Glittre ADL-test þþ –?
Activity monitor DAM ? þþ
Activity monitor PW 610 þ þ
Activity monitor SAB þþ––
Activity monitor Lifecorder PLUS ––
Activity monitor Actiwatch Spectrum ––
Activity monitor AH ?
Activity monitor Actimarker ? ?
Activity monitor SAM ???
Liu et al Medicine Volume 95, Number 20, May 2016
12 |www.md-journal.com Copyright #2016 Wolters Kluwer Health, Inc. All rights reserved.
Category Instrument
Box A
Internal
Consistency
Box B
Reliability
Box C
Measurement
Error
Box D
Content
Validity
Box E
Structural
Validity
Box F
Hypothesis
Testing
Box G
Cross-Cultural
Validity
Box H
Criterion
Validity
Box I
Responsiveness
Activity monitor ActivPAL ??
Activity monitor SCAM ?
Activity monitor RT3 ––
Activity monitor Actigraph GT3X ––
Activity monitor Fitty 3 ?
Activity monitor Tritrac R3D
accelerometer
þþ
Activity monitor FB ?
Activity monitor PAM ?
PRO LCADL ? þþþ–
PRO FPI ? þþþ þþ þþþ
PRO FPI-SF ? þþ þþþ þþ ?
PRO LCOPD þþ þþ þþ þþ þþ ?
PRO CARS þ?þþ þ
PRO UCDQ þþþ?
PRO ADL-D ? þ
PRO DIRECT þþ þ
PRO SOBDA þþþ þþþ ––– þþ ?
PRO CDLM ? þþ?
PRO PFSDQ-M ? ???
PRO PFSS þ??–þ
PRO PFSS-11 þþ ?þþ þ ?
PRO DASI þþ ––
PRO MRADL þþ for mail;
þfor face to
face
10MGS ¼10-meter gait speed, 10MGS ¼10-meter gait speed, 12MD ¼12-minute distance walk, 2MWT ¼2-minute walk test, 30MWT ¼30-meter walk test, 3CRT ¼3-minute chair rise test,
4MGS ¼4-meter gait speed, 4MGS ¼4-meter gait speed, 5STS ¼Five-repetition sit-to-stand test, 6MST ¼6-minute step test, 6MWT ¼6-minute walk test, ADL-D ¼activity of daily living dyspnea
scale, AH ¼ActiHeart, CARS ¼COPD activity rating scale, CDLM ¼capacity of daily living during the morning questionnaire, DAM ¼DynaPort activity monitor, DASI ¼Duke activity status index,
DIRECT ¼disability related to COPD tool, ESWT ¼endurance shuttle walking test, FPI ¼functional performance inventory, FPI-SF ¼functional performance inventory short form, GST ¼grocery
shelving task, ISWT/SWT ¼incremental shuttle walk test, LCADL ¼London chest activity of daily living scale, LCOPD¼living with COPD questionnaire, M6MWT ¼modified 6-minute walk test,
MRADL ¼Manchester respiratory activities of daily living questionnaire, MSWT ¼modified SWT, PBRT ¼6-minute pegboard and ring test, PFSDQ-M ¼pulmonary functional status and dyspnea
questionnaire-modified, PFSS ¼pulmonary functional status scale, PFSS-11 ¼short-form pulmonary functional status scale, PRO ¼patient-reported outcomes, PW ¼power walker, SAB ¼SenseWear
armband, SAM ¼StepWatch
TM
activity monitor, SCAM ¼self-contained activity monitor, SCPT ¼stair climb power test, SOBDA ¼shortness of breath with daily activities, SRAT ¼steep ramp
anaerobic test, STST ¼sit-to-stand test, TChester ¼Chester step test, UCDQ ¼University of Cincinnati dyspnea questionnaire, UULEX ¼unsupported upper limb exercise test.
?¼indeterminate rating, þ¼positive rating, – ¼negative rating.
Medicine Volume 95, Number 20, May 2016 Functional Status Assessment in Patients With COPD
Copyright #2016 Wolters Kluwer Health, Inc. All rights reserved. www.md-journal.com |13
practice, this review recommends 10 out or 57 instruments
assessing functional status of COPD patients. More importantly,
it demonstrates how to choose suitable measures according to
both the studies on elevating these measures and the require-
ments of clinical practice.
Comparing Performance-Based Measures with
Patient-Reported Measures
According to the summary of best-evidence synthesis,
performance-based measures did not have as much positive
evidence on measurement property in comparison to patient-
reported measures. The lack of adequate positive evidence
contradicts their present importance in measuring functional
status in COPD patients. Performance-based measures objec-
tively measure what patients actually do by assessing indicators
like timing, counting, and distance.
137
It was believed to be
more likely to fully characterize a change in functional status
than patient-reported measures alone.
138
Some of these per-
formance-based measures have been widely approved and used
for many years to evaluate treatment effect, to assess health
status, and to explore etiology. For example, 6MWT is a widely
used walking test in clinical practice, and it was often used as a
standard for other instruments.
139– 142
However, its positive
evidence confined to reliability, which is also a common
situation in all performance-based measures. Activity monitors
capture the patients’ activities of daily living. They are an
essential supplement to laboratory tests. Although there are
numerous studies (27 studies), the qualities of these studies were
poor (16 poor studies), leading to a weaker positive rating in
evidence synthesis. More good quality studies need to be
conducted in order to assess the measurement properties of
these performance-based measures.
Weakness Limiting the Quality and Neglected
Measurement Properties in the Existing Studies
on Performance-Based Measures and Patient-
Reported Measures
The methodological qualities of the studies included in this
review ranged from poor to excellent.Good and excellent
quality studies only took up 20% of all studies. In terms of
performance-based measures, inadequate sample size was one
major drawback, probably because performance-based
measurements are more difficult to conduct. Some studies on
performance-based measures had a sample size
<10.
37,47,66,71,90,105
The sample size should be enlarged in
future similar studies according to COSMIN criterion, which
is 100 for excellent, 50– 99 for good, 30–49 for fair, and <30
for poor. However, one thing to note is that the COSMIN
checklist was originally developed to assess studies focusing
on patient-reported measures. Considering the differences in
instrument characteristics and study designs between studies on
performance-based measures and studies on patient-reported
measures, the sample size criteria may need some adjustment.
Methodology on performance-based measures should be dis-
cussed in the future. Another obvious drawback affecting
studies on performance-based measures was that methods did
not meet the COSMIN criteria. For example, some studies
measuring reliability tend to not calculate the ICC or Pearson
or Spearman correlations, no correlation was calculated with
other comparative instruments, whereas only Pvalues were
used when testing responsiveness, and no adequate hypotheses
were formulated a priori. Qualities of studies on patient-
reported measures were better than studies on performance-
based measures (Table 5). However, checking for unidimen-
sionality, enlarging sample sizes, and formulating hypotheses a
priori may further improve all study quality.
According to the results, the included studies and positive
evidence were confined to several measurement properties.
Some important measurement properties, including content
validity and responsiveness, were neglected or poorly reported.
Content validity examines the extent to which the concepts of
interest are comprehensively represented by the items of the
questionnaire,
24,143
so it is especially important for studies on
patient-reported measures. To measure content validity, a clear
concept model is to be developed.
144
However, present PROs
that aim to measure physical activity in chronic respiratory
disease patients or similar populations (chronic heart disease
patients or the elderly) are rarely based on a conceptual frame-
work.
145
Additionally, a standard method to assess content
validity should be applied. According to COSMIN, an appro-
priate method is to have experts and the target population to
assess the relevance and comprehensiveness of the instrument
(s) based on criteria set by COSMIN. The two studies on content
validity measurement were determined to be poor because they
did not meet the above-mentioned criterion. Responsiveness is
another key issue for future studies on both performance-based
measures and patient-reported measures. An important role of
functional status measurement is the evaluation of the effect of
rehabilitation or treatment. Therefore, it is important for
measurement instruments to respond to change. In the present
studies measuring responsiveness, the rating of poor was given
because of inadequate sample size. Also, most fair studies used
Pvalues instead of showing correlation with comparative
instruments or with AUC values. Further studies exploring
the responsiveness of functional status instruments should be
conducted by applying appropriate methods.
Choosing Measures According to the Present
Evidence
Valid and systematical measures of COPD patients’ health
status are the base of the accurate quantification of the therapy
effects. Facing an impressive and increasing number of
measures assessing functional status of COPD patients, clin-
icians might be confused and feel difficult to find one measure
satisfying all of their demands. Another source of confusion is
the inconsistent conclusions of reports which employed various
measures to evaluate the effect of therapy. It is difficult for
clinicians to choose best care for patients by comparing and
combining results of these clinical trials.
According to the results, none of measures has been tested
for all measurement properties. However, the existing evidence
demonstrates that some instruments perform better: 6MWT,
endurance treadmill test, and usual 4MGS; and FPI, FPI-SF,
LCOPD, CARS, UCDQ, SOBDA, and PFSS-11. These instru-
ments should be preferred in future studies and clinical practice
(Table 7). 6MWT was proven to predict the survival in COPD
patients well.
146– 148
Usual 4MGS needs much shortercourse than
6MWT, making it useful for frail patients and applicable in most
healthcare settings (including home). MCID was reported to be
0.11 m/s.
77
It is worth to be considered as an instrument for health
management of COPD patients. Endurance treadmill test can
clearer reflect the physiological limitations.
67
FPI, FPI-SF,
LCOPD, CARS, UCDQ, SOBDA, and PFSS-11 are different
in terms of their measurement focus and the length of scales. In
other words, each measure has its own advantage and most
suitable domain. Thus, researchers and clinicians should employ
Liu et al Medicine Volume 95, Number 20, May 2016
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TABLE 7. Characteristics of Recommended Instruments
Instrument Category
Measurement Content
and Protocol Output
Time to
Administer
Environment to
Administer
6MWT Exercise testing Quickly walk on a flat,
hard surface in a period
of 6 min
Distance – A 100-ft hallway which is
indoors, along a long,
flat, straight, enclosed
corridor with a hard
surface that is seldom
traveled
Usual 4MGS Exercise testing Walk at usual speed Time taken to
complete the 4-m
course
<2 min A 4-m flat, unobstructed
course marked out with
tape
Endurance
treadmill
test
Exercise testing Walking on a treadmill
with a fixed percentage
of the maximum work
rate applied as a
constant work rate
Time to exhaustion – Treadmill
FPI Patient-reported Body care, household
maintenance, physical
exercise, recreation,
spiritual activities, and
social activities
1–4 (þthe activity
is not performed
for reasons other
than health)
65 items –
FPI-SF Patient-reported Body care, household,
maintenance, physical
exercise, recreation,
spiritual activities, and
social activities
Three-point scale 32 items –
LCOPD Patient-reported Self-actualization needs,
safety and security
needs, Independence
needs, self-esteem
needs, control needs,
social and relationship
needs
‘‘True’’ (scored 1)
and ‘‘not true’’
(scored 0)
response options
22 items –
CARS Patient-reported Self-care activity,
domestic activity,
outdoor activity, social
interaction activity
2 (completely
independent), 1
(partially
dependent), 0
(dependent)
12 items –
UCDQ Patient-reported Breathlessness during
physical activity,
breathlessness during
speaking activities,
when speaking during
physical activity
1–5 (þnot
interested)
30 items –
SOBDA Patient-reported Different levels of
exertion and body
positions which impact
patient’s experience of
SOB
A scale from ‘‘not at
all’’ to ‘‘so short
of breath that I did
not do the
activity’’
13 items –
PFSS-11 Patient-reported Physical functioning,
emotional functioning
A 5-point Likert-
type response
11 items –
Primary outcome measures are shown here.4MGS ¼4-meter gait speed, 6MWT ¼6-minute walk test, CARS ¼COPD activity rating scale, SOB,
FPI ¼functional performance inventory, FPI-SF ¼functional performance inventory short form, LCOPD ¼living with COPD questionnaire,
PFSS ¼pulmonary functional status scale, SOB ¼shortness of breath, SOBDA ¼shortness of breath with daily activities, UCDQ ¼University
of Cincinnati dyspnea questionnaire.
Medicine Volume 95, Number 20, May 2016 Functional Status Assessment in Patients With COPD
Copyright #2016 Wolters Kluwer Health, Inc. All rights reserved. www.md-journal.com |15
those measures whose measurement properties alignment to their
purposes. For example, if the instruments were to be used to
measure the therapeutic effect of pulmonary rehabilitation or a
respiratorymedicine, then the responsivenessof the measurement
instruments should be preferred. Finally, functional status
measurement of COPD patients is complex, as it contains multi-
dimensional constructs. Different types of instruments have their
own strength. It was suggested that both types of measures—
performance-based measures and patient-reported measures—
are complementary rather than competing when assessing func-
tional status of COPD patients.
149
Finding an optimal combi-
nation of measures from both types is worth for further research.
LIMITATIONS
This study has several limitations. First, some comprehen-
sive HRQOL instruments, including dimensions measuring
functional status were excluded in our study. The reason is
that their reliability and validity were calculated for the whole
instrument rather than the dimension of interest, functional
status. Second, some studies focusing on evaluating the therapy
effect were excluded because they failed to provide enough
information on measurement properties. Admittedly, reviewing
measurement properties for a certain type of therapy is inter-
esting and valuable for clinical practice, which should be
implemented in the future.
In summary, further research is needed to evaluate the
measurement properties of performance-based measures
because there is a lack of available information and present
studies lack in quality. Content validity and responsiveness
should be fully assessed in all instruments, and sample size
needs to be enlarged. As for choosing measurement tools for
functional status in COPD patients, we recommend FPI, FPI-
SF, LCOPD, CARS, UCDQ, SOBDA, PFSS-11, 6MWT, endur-
ance treadmill test, and usual 4MGS. These instruments are
different in their measurement content or administer require-
ment, which may tailor to different usage in clinical practice.
We also recommend selecting instruments that perform well in
certain measurement properties required for certain assessment
purposes and combining instruments from both measurement
types.
ACKNOWLEDGMENTS
The authors thank Terwee CB for providing us permission
to use the COSMIN checklist and instruction to do the systema-
tic review using COSMIN. We also thank Weldam, S.W.M., for
responding to their consultation about quality criteria for
measurement properties in his article. We thank Nan Jiang
for her kind help with correcting English of the manuscript.
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