Patient-Reported Outcome Measures of Quality of Life in People Affected by Diabetic Foot: A Psychometric Systematic Review

Abstract

Objectives
This psychometric systematic review aimed to identify the most suitable patient-reported outcome measures (PROMs) of quality of life (QoL) in people affected by diabetic foot.

Methods
We performed a literature search in MEDLINE (PubMed), CINAHL (EBSCOhost), and PsycINFO (EBSCOhost) databases from inception to February 1, 2022. We also searched gray literature databases. Eligible studies were full-text reports developing a QoL condition-specific PROM or assessing one or more of its measurement properties in people affected by diabetic foot. We assessed the methodological quality of included studies independently using the “Consensus-Based Standards for the Selection of Health Measurement Instruments Risk of Bias” checklist. The measurement properties were evaluated using specific criteria. We graded the quality of the evidence using a “Grading of Recommendations Assessment, Development and Evaluation” approach modified by Consensus-Based Standards for the Selection of Health Measurement Instruments.

Results
Forty-three reports (46 studies) providing information on the measurement properties of 10 different PROMs were included. We did not identify any instruments that could be recommended for use. We identified 2 PROMs that were not recommended for use and 8 that were potentially recommended but would require further investigation. Of these 8 PROMs, 4 had better evidence for content validity.

Conclusions
Available PROMs to measure QoL in people affected by diabetic foot have limited evidence for their measurement properties. There is no fully suitable PROM. Pending further evidence, 4 PROMs could potentially be recommended for use.

Full text

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Contents lists available at sciencedirect.com
Journal homepage: www.elsevier.com/locate/jval
Patient-Reported Outcomes
Patient-Reported Outcome Measures of Quality of Life in People Affected
by Diabetic Foot: A Psychometric Systematic Review
Àngel Romero-Collado, PhD, Elvira Hernández-Martínez-Esparza, PhD, Edurne Zabaleta-del-Olmo, PhD,
Ana-María Urpí-Fernández, PhD, Rosalía Santesmases-Masana, PhD
Objectives: This psychometric systematic review aimed to identify the most suitable patient-reported outcome measures
(PROMs) of quality of life (QoL) in people affected by diabetic foot.
Methods: We performed a literature search in MEDLINE (PubMed), CINAHL (EBSCOhost), and PsycINFO (EBSCOhost) databases
from inception to February 1, 2022. We also searched gray literature databases. Eligible studies were full-text reports
developing a QoL condition-specific PROM or assessing one or more of its measurement properties in people affected by
diabetic foot. We assessed the methodological quality of included studies independently using the “Consensus-Based
Standards for the Selection of Health Measurement Instruments Risk of Bias”checklist. The measurement properties were
evaluated using specific criteria. We graded the quality of the evidence using a “Grading of Recommendations Assessment,
Development and Evaluation”approach modified by Consensus-Based Standards for the Selection of Health Measurement
Instruments.
Results: Forty-three reports (46 studies) providing information on the measurement properties of 10 different PROMs were
included. We did not identify any instruments that could be recommended for use. We identified 2 PROMs that were not
recommended for use and 8 that were potentially recommended but would require further investigation. Of these 8 PROMs, 4
had better evidence for content validity.
Conclusions: Available PROMs to measure QoL in people affected by diabetic foot have limited evidence for their measurement
properties. There is no fully suitable PROM. Pending further evidence, 4 PROMs could potentially be recommended for use.
Keywords: diabetic foot, patient-reported outcome measures, psychometrics, quality of life, systematic review
VALUE HEALTH. 2022; -(-):-–-
Introduction
Diabetic foot is defined as the “infection, ulceration, or
destruction of tissues of the foot of a person with currently or
previously diagnosed diabetes mellitus, usually accompanied by
neuropathy and peripheral arterHy disease in the lower extrem-
ity.”
1
Its complications, which often result in amputation, are a
leading cause of the global burden of disability; therefore, it
constitutes a major public health problem
2,3
with significant
adverse consequences on the healthcare system and health eco-
nomics.
4
Moreover, people affected by diabetic foot have a poorer
quality of life (QoL) than people affected by diabetes but without
diabetic foot.
5
In addition, poor QoL is associated with a worse
diabetic foot prognosis.
6
Therefore, QoL is a crucial subject in the
area of diabetic foot.
7
Patient-reported outcome measures (PROMs) are standardised
measures to quantify the patient’s perspective and help under-
stand how the disease, the health system, and healthcare impact
patients.
8
They also enable patient-centered care management
and are helpful indicators for comparing different health services
or providers from the point of view of quality improvement.
8,9
Measurement instruments that measure QoL are a class of
PROMs.
9
They yield a global summary of wellbeing and can be
generic or condition specific. Using generic QoL measurement
instruments, such as the EQ-5D or the Medical Outcomes Study
Short Form Short Form 36-Item (SF-36) (and related measures),
helps assess individuals and compare groups with and without a
health condition.
9,10
Nevertheless, they may underestimate
changes in QoL in specific populations and may not capture spe-
cific problems related to a particular condition or disease.
9
In this
sense, the condition-specific PROMs provide additional and
complementary information on the person’s QoL.
9,11
Psychometric systematic reviews are valuable tools for select-
ing PROMs for research and clinical practice and identifying crit-
ical gaps in knowledge on their quality.
12
In this regard, the
Consensus-Based Standards for the Selection of Health Measure-
ment Instruments (COSMIN) initiative has recently emerged to
improve the selection of PROMs by developing tools to select the
most suitable PROM for a given purpose.
13
Among these tools are
the methodological guidelines for psychometric systematic re-
views of PROMs.
14-16
Previous systematic reviews have summa-
rized and analyzed the PROMs of QoL used in the spectrum of
diabetes-related foot disease.
17-21
Nevertheless, Hogg et al
17
did
not conduct their review following the COSMIN guidelines.
1098-3015/Copyright ª2022, International Society for Pharmacoeconomics and Outcomes Research, Inc. Published by Elsevier Inc. This is an open access article
under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Therefore, critical aspects of a review of this nature can be
improved, especially the search strategy, the quality assessment of
the included studies and the included PROMs, and the data syn-
thesis.
22
Smith et al
20
conducted their review according to COS-
MIN guidelines; nevertheless, it focuses on assessing PROMs of
QoL in people affected by diabetic neuropathy. Finally, the
remaining 3 reviews focus on a broad range of PROMs,
18,19,21
not
exclusively on those measuring QoL.
To address these issues, we conducted a psychometric sys-
tematic review to identify the most suitable PROMs of QoL in
people affected by diabetic foot.
Methods
We conducted this review following the COSMIN initiative.
14-16
This review is reported according to the Preferred Reporting Items
for Systematic Reviews and Meta-Analyses 2020 statement
23
and
the Preferred Reporting Items for Systematic Reviews and Meta-
Analyses literature search extension.
24
The review protocol was
registered in the International Prospective Register of Systematic
Reviews (PROSPERO) on August 6, 2018 (registration number:
*Blinded for review*); no changes have been made tothe protocol.
Eligibility Criteria and Information Sources
We performed a literature search in MEDLINE (PubMed),
CINAHL (EBSCOhost), and PsycINFO (EBSCOhost) databases. We
also searched the gray literature on OpenGrey and Grey Literature
Report databases. Reports were eligible if they met the following
criteria: (1) the PROM had to be a disease-specific and not a
generic measure of QoL, (2) the whole or a part of the study
population was people affected by diabetic foot,
1
and (3) the aim
of the study was the development of a PROM, the evaluation of
one or more of its measurement properties, or the evaluation of its
interpretability and feasibility. Studies that use only the PROM as
an outcome measure (eg, clinical trials) or those used to validate
another measurement instrument were excluded. We only
included full-text articles because minimal information on a study
is often found in abstracts. Measurement instruments develop-
ment studies were also included even if these studies did not
involve people affected by diabetic foot.
Search Strategy
A comprehensive literature search was initially performed to
identify studies published from databases inception to February 1,
2022. We combined terms in controlled language and free text.
Likewise, we added a highly sensitive filter developed by COSMIN
for the MEDLINE (PubMed) search to identify studies on PROMs.
25
We imposed no language restrictions on any of the searches. The
reproducible searches for all databases are available at *Blinded
for review; available in an open access repository*. We manually
screened reference lists of included studies. In addition, we con-
tacted with the authors of the included studies to retrieve the
maximum possible information about the identified PROMs. We
also complemented this initial search with an additional search
for the particular PROMs identified using only the PROM name,
and we browsed the identified PROMs’websites.
Selection Process
We imported the retrieved references into the Rayyan QCRI
web application program.
26
This program facilitated collaboration
among the reviewers during the study selection process. Two re-
viewers manually removed duplicates using Rayyan QCRI’s
duplicate identification strategy. These 2 reviewers independently
assessed the titles and abstracts of the references retrieved, con-
fronting them with the eligibility criteria. If a reference seemed
relevant to at least one of the reviewers, the full text of the article
was independently reviewed by these 2 reviewers. Conflicts over
inclusion between these reviewers were discussed, and a third
reviewer was consulted in case of not reaching a consensus.
Data Analysis
Included studies were grouped by PROM to identify the
number of studies and PROMs separately. First, we assessed the
methodological quality of every single study using the “COSMIN
Table 1. COSMIN definitions of measurement properties.
14-16
Measurement property Definition
Content validity The degree to which the content of a PROM is an adequate reflection of the construct to be
measured
Criterion validity The degree to which the scores of a PROM are an adequate reflection of a “gold standard”
Cross-cultural validity The degree to which the performance of the items on a translated or culturally adapted PROM
are an adequate reflection of the performance of the items of the original version of the PROM
Hypotheses testing for construct validity The degree to which the scores of a PROM are consistent with hypotheses (for instance with
regard to internal relationships, relationships to scores of other instruments, or differences
between relevant groups) based on the assumption that the PROM validly measures the
construct to be measured
Internal consistency The degree of the interrelatedness among the items
Measurement error The systematic and random error of a patient’s score that is not attributed to true changes in the
construct to be measured
Reliability The extent to which scores for patients who have not changed are the same for repeated
measurement under several conditions: eg, over time (test-retest), by different persons on the
same occasion (inter-rater), or by the same persons (ie, raters or responders) on different
occasions (intra-rater)
Structural validity The degree to which the scores of a PROM are an adequate reflection of the dimensionality of
the construct to be measured
Responsiveness The ability of a PROM to detect change over time in the construct to be measured
COSMIN indicates Consensus-Based Standards for the Selection of Health Measurement Instruments; PROM, patient-reported outcome measure.
2VALUE IN HEALTH -2022

risk of bias”checklist.
14
We analyzed the following measurement
properties: content validity, construct validity (structural validity,
hypotheses testing, and cross-cultural validity), criterion validity,
reliability (internal consistency, test-retest reliability, and mea-
surement error), and responsiveness (see definitions of each
measurement property in Table 1
14-16
). Concerning criterion val-
idity, we agreed, based on the COSMIN guidelines,
14,15
that no gold
standard exists for identified PROMs. The only exception is when a
shortened instrument is compared with the original long version.
In this case, we considered the original long version as the gold
standard. When the studies compared the study PROM scores
with a widely used instrument such as the SF-36, it was consid-
ered a construct validation.
27
Regarding hypothesis testing for
construct validity and responsiveness, in accordance with COSMIN
guidelines, it was not the Pvalues but the direction and magnitude
of the observed correlations that were taken into account. Thus,
the review team agreed that correlations (changes in) of at least
0.50 between the PROM under study and a comparison instru-
ment measuring the same construct would be interpreted as
adequate and correlations from 0.30 to 0.50 between instruments
measuring related but dissimilar constructs.
14-16
We determined
which measurement properties were to be assessed in each study
and rated the methodological quality of each of these studies as
“very good,”“adequate,”“doubtful,”or “inadequate.”Second, ev-
idence of every single study was rated against criteria for good
measurement properties as “sufficient,”“insufficient,”and “inde-
terminate.”
15
Third, the evidence was summarized per measure-
ment property per PROM. Regarding hypothesis testing for
construct validity, the results of all studies by PROM were taken
together. We decided that the evidence was sufficient if 75% or
more of the hypotheses were confirmed.
14-16
We pooled the test-
retest reliability coefficients of the measurement instruments by
the meta-essentials tool for correlational data version 1.5.
28
We
used random-effects models based on the diversity of the popu-
lation studied. The extent and impact of study heterogeneity were
assessed by the tau
2
and the I
2
statistics, respectively. We sum-
marized the rest of the measurement properties qualitatively. The
overall result was rated against the criteria for good measurement
properties. Finally, the quality of the evidence was graded by using
a“Grading of Recommendations Assessment, Development and
Evaluation”approach modified by COSMIN.
15
This approach uses 4
factors to determine the quality of the evidence: (1) risk of bias
(methodological quality of the studies), (2) inconsistency of the
results of the studies, (3) inaccuracy (small population sample
size), and (4) indirect evidence (evidence from different pop-
ulations not strictly related to the target population, in our case,
eg, people affected by chronic wounds in general). We discussed a
priori how ratings should be determined, and we piloted the
ratings with a few articles from the review to take the scope of the
review into account. All ratings were done by all the reviewers
independently. We had regular consensus meetings to discuss
rating issues and to ensure they were rated consistently. Infor-
mation on the included studies and the identified PROMs was
collected in the data extraction spreadsheets developed by COS-
MIN (available at https://cosmin.nl/wp-content/uploads/Scoring-
form-COSMIN-boxes_april_final.xlsx). Interpretability and
feasibility are not considered measurement properties, but they
are essential aspects when selecting a PROM. Therefore, we also
collected in specific tables these aspects and described them.
Based on the available evidence and its quality grade, we made
recommendations for use per each PROM identified. These
evidence-based recommendations were classified into 3 cate-
gories according to COSMIN guidelines
14-16
: (1) PROMs whose
content validity had sufficient evidence and at least a low quality
of evidence for a sufficient internal consistency of its scores, (2)
PROMs with high-quality evidence for an insufficient
Figure 1. PRISMA 2020 flow diagram.
(n = 1433)
(n = 457)
(n = 898)
(n = 75)
(n = 1)
(n = 2)
(n = 23)
(n = 8)
(n = 14)
(n = 1)
(n = 43)
(n = 46)
(n = 10)
(n = 19):
(n = 3)
(n = 4)
(n = 3)
(n = 7)
(n = 1)
(n = 1)
(n = 23) (n = 0)
(n = 8):
(n = 1)
(n = 5)
(n = 1)
(n = 1)
PRISMA indicates Preferred Reporting Items for Systematic Reviews and Meta-Analyses.
-- 3

Table 2. Characteristics of the included PROMs.
PROM
(reference to
the first
article)
Target
population
Mode of
administration
Recall
period
(Sub)scale(s)
(number of
items)
Response
options
Range of
scores/scoring
Original
language
Available
translations
AOFAS-DFQ
36
People
affected by
diabetes and
Charcot
arthropathy
Self-
administration
1 week - 66 questions,
many of which
were multi-
item in nature
- It is organized
into 5 sections:
demographic
data, general
health (SF-36),
foot problem
and diabetes,
health condi-
tions, and foot
care.
Items are not
all on a
common
metric system;
some items
have scores
such as 0/1 and
others on and
5-point or 6-
point Likert
scale.
- Items are used
to compute
scores in 6
sections: (1)
general health,
(2) physicality,
(3) emotion, (4)
worry, (5) foot
status, and (6)
care.
- Each section
has many sub-
scales: general
health (6 sub-
scales), physi-
cality (6
subscales),
emotion (7
subscales),
worry (4 sub-
scales), foot
status (2 sub-
scales), and
care (4
subscales).
- Each domain is
transformed to
create scores
that range
from 0 to 100.
- Higher scores =
better QoL
English
(USA)
NIA
CWIS
51
People
affected by
chronic
wounds
Self-
administration
1 week - 26 items
divided into 3
subscales:
physical symp-
toms and
everyday living
(experienced
and stressful-
ness of experi-
ence) (12
items), social
life (experi-
enced and
stressfulness
of experience)
(7 items), and
wellbeing (7
items).
- Two added
items that
measure global
QoL and satis-
faction with
QoL.
- 5-point Likert
scale for 26
items
- 11-point
Likert scale
for the 2
added items
- Items for each
scale are sum-
mated and
transformed
onto a 0-100
scale.
- High scores =
better QoL
English
(UK)
Chinese
Dutch
English
(USA)
French
German
Italian
Portuguese
Sinhalese
Spanish
(Mexico and
Spain)
Swedish
Tao
Welsh
continued on next page
4VALUE IN HEALTH -2022

Table 2. Continued
PROM
(reference to
the first
article)
Target
population
Mode of
administration
Recall
period
(Sub)scale(s)
(number of
items)
Response
options
Range of
scores/scoring
Original
language
Available
translations
DFS
29
People
affected by
DFU
Patient and
caregiver self-
administration
versions
Different
recall
periods
are
available:
- The last
4 weeks
- Now
-No
recall
period
version
64 items:
- 58 items are
grouped into
11 scales: lei-
sure (5 items),
physical health
(6 items), daily
activities (6
items), emo-
tions (17
items),
noncompliance
(2 items), fam-
ily (5 items),
friends (5
items), treat-
ment (4 items);
satisfaction (1
item), positive
attitude (5
items), and
financial (2
items).
- 6 items
addressing
employment-
related issues
- 5-point Likert
scale ranging
from 1 “not at
all”or “none
of the time”
to 5 “a great
deal”or
“extremely”
- Some items
have an
additional
0“not appli-
cable”option.
- For the
employment-
related items,
2 additional
response
options are
used:
dichotomous
(yes/no) and
a 6-point
Likert scale.
- Scores are
based on the
sum of all
items associ-
ated with each
subscale (raw
item scores are
reverse coded
when
necessary).
- The scores per
dimension
range between
0 and 100.
- Items address-
ing
employment-
related issues
are not used to
compute
scores.
- Higher scores =
better QoL
English
(UK)
Czech
Danish
Dutch
English (USA)
French
Indonesian
Italian
Norwegian
DFS-SF
33
People
affected by
DFU
Self-
administration or
interview-
administration
Different
recall
periods
are
available
- Now
- The last
4 weeks
29 items
grouped into 6
subscales:
- Leisure (5
items)
- Physical health
(5 items)
- Negative emo-
tions (6 items)
- Dependence/
daily life (5
items)
- Worried about
ulcers/feet (4
items)
- Bothered by
ulcer care (4
items)
5-point Likert
scale ranging
from 1 “not at
all”or “none of
the time”to 5
“a great deal”
or “all the time”
or “extremely”
- Domain scores
are based on
the sum of all
items associ-
ated with each
subscale (raw
item scores are
reverse coded
when
necessary).
- The scores per
dimension are
transformed
on a scale from
0 to 100.
- Higher scores =
better QoL
- Danish
- Dutch
- English
UK and
USA
- French
- German
- Italian
Arabic (Jordan)
Bahasa
Chinese (Hong
Kong)
French (Canada)
Greek
Korean
Kannada (India)
Polish
Portuguese
(Brazil)
Spanish (Spain
and USA)
Turkish
HRQLQDFU
44
People
affected by
DFU
Self-
administration
Now 20 items that
included 6
domains:
physical health,
physical
symptoms, daily
activity,
emotional status,
social status, and
financial effect
Likert-type 4-
point rating
scale
- Scores are
based on the
sum of all
items associ-
ated with each
domain.
- Higher score =
better QoL
English
(India)
NIA
continued on next page
-- 5

Table 2. Continued
PROM
(reference to
the first
article)
Target
population
Mode of
administration
Recall
period
(Sub)scale(s)
(number of
items)
Response
options
Range of
scores/scoring
Original
language
Available
translations
NeuroQoL
59
People
affected by
diabetic
peripheral
neuropathy
and foot
ulcers
Self-
administration
and interview-
administration
Last 4
weeks
35 items
- 13 items assess
specific so-
matic experi-
ences in 3
domains.
- 14 items assess
specific func-
tional, social,
and emotional
experiences in
3 domains.
- A single item
assesses the
quality of life in
each of the 6
domains.
- Two final items
in the scale
assess overall
satisfaction or
QoL, one item
requesting that
the patient
make a judg-
ment specific
to his or her
experience
with foot prob-
lems, and a
final item
asking for an
overall judg-
ment of QoL.
5-point Likert
scale: never to
all of the time
- For each of 27
specific items,
patients are
asked to judge
the degree to
which the so-
matic experi-
ence, restric-
tion of
activities, social
function, and
emotional
states have
been a bother
or important to
them. The
bother/impor-
tance items
were scored as
1 = none, 2 =
some, and 3 =
very.
- Weighted
scores are
calculated by
multiplying the
scale score by
the corre-
sponding
bother/impor-
tance score.
- Higher score =
worst QoL
English
(USA and
UK)
Arabic (Jordan)
Portuguese
(Brazil)
Norfolk QoL-
DN
60
People
affected by
diabetic
neuropathy
Self-
administration - The last
4 weeks
(39
items)
- Now (8
items)
47 items divided
into 5 subscales:
physical (1)
functioning/large
fiber (15 items),
(2) ADLs (5
items), small
fiber (4 items),
symptoms (8
items), and
autonomic (3
items)
- 8 items were
excluded from
the final facto-
rial analysis
- 4 items about
the duration of
symptoms, na-
ture of symp-
toms, and
medications
(these items
are not
included in the
scoring of any
of the scales)
- Items 1-7,
scores for
each symp-
tom equal
the number
of body sites
for which a
symptom is
reported.
- Items 12-15,
“yes”or “no”
Items 16-46, a
5-point Likert-
type scale
- For item 47, 3
possible re-
sponses: 1-2,
3-4, or 5 or
more
medications
- The subscales
are calculated
without
weighting and
reported as the
sum of the
questionnaire
items related
to each
subscale.
- Items 8-11 are
for clinical pur-
poses and not
included in the
scoring
- Higher score =
worst QoL
English
(USA)
German
continued on next page
6VALUE IN HEALTH -2022

Table 2. Continued
PROM
(reference to
the first
article)
Target
population
Mode of
administration
Recall
period
(Sub)scale(s)
(number of
items)
Response
options
Range of
scores/scoring
Original
language
Available
translations
Quality of life
instrument
54
People
affected by
chronic
wounds
Interview-
administration
Now 20 items
included 6
domains:
physical
activities,
feelings,
household
duties, leisure
time activities,
social relations,
and general
activities.
5-point rating
scale - Scores above
the mean (17
points) were
classified as
satisfactory
and those
below
unsatisfactory.
- Higher scores =
better QoL
English
(India)
NIA
Wound-QoL
34
People
affected by
chronic
wounds
Self-
administration
and interview-
administration
1 week 17 items into 3
subscales: “body”
(5 items);
“psyche”(5
items), and
“everyday life”(6
items)
- One item as-
sesses the
financial
burden (does
not belong to
either of the
subscales).
Each item has 5
possible
answers: no at
all, a little,
moderately,
quite a lot. and
very much
(scores ranged
from 0 to 4).
- A global score
on overall
disease-
specific quality
of life is
computed by
averaging all
items. It can
only be
computed if at
least 75% of
the items have
been
answered.
- Subscales
scores can be
calculated by
averaging the
individual
items. A sub-
scale can only
be computed if
no .1 item of
the subscale is
missing.
- Higher scores =
worst QoL
German
(Germany
and
Austria)
Arabic (Israel)
Chinese (China)
Czech
Danish
Dutch (The
Netherlands)
English
(Canada, UK,
and USA)
German
(Switzerland)
Hebrew
French
Italian
Latvian
Lithuanian
Polish
Portuguese
(Brazil and
Portugal)
Russian
Slovakian
Spanish
(Central
America and
Spain)
Swedish
Turkish
Wound-QoL
revised
version
70
People
affected by
chronic
wounds
Self-
administration
and interview-
administration
1-week 14 items into 3
subscales: “body”
(4 items);
“psyche”(4
items), and
“everyday life”5
items)
- One item as-
sesses the
burden (does
not belong to
either of the
subscales).
Each item has 5
possible
answers: no at
all, a little,
moderately,
quite a lot, and
very much
(scores ranged
from 0 to 4).
Higher scores =
worst QoL
German Dutch (The
Netherlands)
English
German
Hebrew
Spanish (Spain)
Swedish
ADL indicates activity of daily living; AOFAS-DFQ, American Orthopaedic Foot and Ankle Society Diabetic Foot Questionnaire; CWIS, Cardiff Wound Impact Schedule/
Scale; DFS-SF, Diabetic Foot Ulcer Scale-Short Form; DFU, diabetic foot ulcers; HRQLQDFU, Health-Related Quality Of Life Questionnaire in Diabetic Foot; NeuroQoL,
Neuropathy- and Foot Ulcer-Specific Quality of Life; NIA, no information available; Norfolk QoL-DN, Norfolk Quality of Life-Diabetic Neuropathy; PROM, patient-
reported outcome measure; QoL, quality of life; SF-36, Short Form 36-Item; UK, United Kingdom; USA, United States of America.
-- 7

Table 3. Quality of the PROM development and the studies on measurement properties.
PROM/studies Instrument
development
Content
validity
Structural
validity
Asking patients Asking experts
Relevance Comprehensiveness Comprehensibility Relevance Com prehensiveness
AOFAS-DFQ
Dhawan et al
36
I
CWIS
Price and Harding
51
D I
Acquadro et al
30
D
Goodridge et al
40
Jaksa and Mahoney
43
Fagerdahl et al
37
D
Huang et al
41
D D
Sriyani et al
56
D
Lozano-Platonoff et al
47
D
van Doorn et al
58
D
Granado-Casas et al
64
I A
DFS
Abetz et al
29
D A
Ribu et al
52
Vym
etalová and Zeleníková
62
D
Sari et al
53
I
DFS-SF
Bann et al
33
(Study 1)
33
D A
Bann et al
33
(Study 2)
33
V
Bann et al
33
(Study 3)
33
Hui et al
42
D
Kontodimopoulos et al
45
D
Macioch et al
48
D
Lee
46
D V
Martinez-Gonzalez et al
49
D A
Oliveira Kaizer et al
50
D V
Toygar et al
57
I V
Putri et al
65
HRQLQDFU
Kateel et al
44
I
NeuroQoL
Vileikyte et al
59
D A
Xavier et al
63
D
Ababneh et al
66
D
Norfolk QoL-DN
Vinik et al
60
D A
Vinik et al
61
D A
Quality of life instrument
Shukla et al
54
I
Wound-QoL
Blome et al
34
I A
Augustin et al
32
Deufert and Graml
35
Sommer et al
55
Fagerdahl and Bergström
38
D
Gamus et al
39
I I
Amesz et al
31
I
Sommer et al
67
D V
Conde Montero et al
68
D A
Knudsen et al
69
DD
Stülpnagel et al
70
(Study 1)
70
V
Topp et al
71
Wound-QoL revised version
Stülpnagel et al
70
(Study 2)
70
I V
Note. Empty cells indicate that study (of part of it) was not performed
A indicates adequate; AOFAS-DFQ, American Orthopaedic Foot and Ankle Society Diabetic Foot Questionnaire; CWIS, Cardiff wound impact schedule/scale; D, doubtful;
DFS, diabetic foot ulcer scale; DFS-SF, diabetic foot ulcer scale-short form; HRQLQDFU, health-related quality of life questionnaire in diabetic foot; I, inadequate;
NeuroQoL, neuropathy- and foot ulcer-specific quality of life; Norfolk QoL-DN, Norfolk quality of life-diabetic neuropathy; PROM, patient-reported outcomes measure;
V, very good.
8VALUE IN HEALTH -2022

Table 3. Continued
Internal
consistency
Cross-cultural
validity
Reliability Measurement
error
Criterion
validity
Construct
validity
Responsiveness
Convergent
validity
Known
groups
validity
Comparison
with gold
standard
Comparison
with other
instruments
Comparison
between
subgroups
Comparison
before and after
intervention
VII I
VI VD
V
IVD
VI VD I
V V
VD VD
VVD
VI VD
VD V D
VI V D
V
AD
VI V D
VI V D
D
VVD
VVD
V V
VVD
VA V D
V V
VD
V
I
VVD
VVD
VD
VD DA
VD
D
VVV
IVV
VA
VI V I
V D
VVV V
V D
VDD
VDDVV
VD
V V
VD V
-- 9

measurement property, and (3) PROMs not classified either as A or
as B. PROMs classified as A were recommended for use, and those
classified as B were unrecommended. PROMs classified as C could
be recommended, but a more significant number of studies were
needed to assess their quality. Because we did not find any in-
struments categorized for category A, we based recommendations
for use on those with the best evidence for content validity and
the best issues of interpretability and feasibility among those
categorized in category C.
Results
The literature search and study selection process are detailed
in Figure 1. Forty-six studies (43 reports) providing information on
the measurement properties of 10 different PROMs were
included.
29-71
These identified measurement instruments were
the American Orthopaedic Foot and Ankle Society Diabetic Foot
Questionnaire (AOFAS-DFQ),
36
the Cardiff Wound Impact
Schedule/Scale (CWIS),
30,37,40,41,43,47,51,56,58,64
the Diabetic Foot
Ulcer Scale (DFS),
29,52,53,62
the Diabetic Foot Ulcer Scale-Short
Form (DFS-SF),
33,42,45,46,48-50,57,65
the Health-Related Quality of
Life Questionnaire in Diabetic Foot (HRQLQDFU),
44
the Neuropa-
thy- and Foot Ulcer-Specific Quality of Life (NeuroQoL),
59,63,66
the
Norfolk Quality of Life-Diabetic Neuropathy (Norfolk QoL-DN),
60,61
the Quality of Life Instrument,
54
the Wound-
QoL,
31,32,34,35,38,39,55,67-71
and the Wound-QoL revised version.
70
The characteristics of these PROMs and the included studies are
presented in Table 2
29,33,34,36,44,51,54,59,60,70
and Appendix Table 1
in Supplemental Materials found at https://doi.org/10.1016/j.
jval.2022.04.1737. In addition, the reports that appeared to meet
the eligibility criteria but were excluded and the reasons for
exclusion are listed in Appendix Text 1 in Supplemental Materials
found at https://doi.org/10.1016/j.jval.2022.04.1737.
The summary of the assessments of PROM development and
the methodological quality of the included studies is presented in
Table 3 and Appendix Table 2 in Supplemental Materials found at
https://doi.org/10.1016/j.jval.2022.04.1737.Appendix Table 3 in
Supplemental Materials found at https://doi.org/10.1016/j.jval.2
022.04.1737 provides the ratings of each study against the
criteria for good measurement properties. Finally, the quality of
the evidence is summarized in Table 4.
Content Validity
In 5 of the 10 identified PROMs,
34,36,44,54,70
the development
methodological quality was rated as inadequate because the
design was not performed on a sample representing the target
population. Regarding Wound-QoL design,
34
although members of
the target population participated in it, the selection of items was
based on their quantitative properties and on expert judgment of
their relevance and comprehensibility. Moreover, only the
HRQLQDFU
44
was pilot tested to evaluate comprehensibility and
comprehensiveness in its development stage. Nevertheless, it
appears that the items were not tested in their final form or were
not retested after substantial adjustments. For the remaining 5
PROMs,
29,33,51,59,60
the development methodological quality was
rated as doubtful, given that some methodological issues were not
sufficiently clarified, such as the type of method used in the
qualitative studies, the interviewers’skills, the use of an interview
guide, and details related to the recording and transcription of the
interviews conducted.
We identified 25 studies that analyzed content validity issues
(see Table 3
29-71
). These studies assessed the comprehensibility of
PROMs original versions translated into other languages. The
quality of 20 of these studies was rated as doubtful mainly because
crucial aspects of the methodology used were not sufficiently
clarified. We rated the quality of 5 studies
31,39,53,57,64
as inadequate
because either the method used was inappropriate or respondents
were not asked about the comprehensibility of all items and
response options.
In summary (see Table 4), we graded the content validity
sufficient with moderate evidence for 2 PROMs (DFS and DFS-SF),
low evidence for 4 (CWIS, NeuroQoL, Norfolk-DN, and Wound-
QoL), and very low evidence for 4 (AOFAS-DFQ, HRQLQDFU, QoL
Instrument, and Wound-QoL revised version).
Construct Validity
We did not identify any studies that assessed the structural
validity of the AOFAS-DFQ, the HRQLQDFU, and the QoL Instru-
ment. We rated the structural validity of 3 instruments (DFS,
NeuroQoL, and Norfolk QoL-DN) as indeterminate because the
identified studies did not provide sufficient information to assess
the criteria for good measurement properties. The remaining 4
PROMs showed insufficient evidence for structural validity. The
quality of this evidence was high for DFS-SF, moderate for the
Wound-QoL and the Wound-QoL revised version, and low for the
CWIS (see Table 4). Hypotheses testing for construct validity was
assessed in 7 PROMs (CWIS, DFS, DFS-SF, NeuroQoL, Norfolk QoL-
DN, QoL Instrument, and Wound-QoL). The results of the
convergent and discriminative validity tests are described in
Appendix Table 3 in Supplemental Materials found at https://doi.
org/10.1016/j.jval.2022.04.1737. Regarding this measurement
property, only one of these PROMs, the NeuroQoL, showed suffi-
cient evidence with a moderate quality (see Table 4). Cross-
cultural validity was assessed in 2 PROMs (the Wound-QoL and
the Wound-QoL revised version) and was considered sufficient for
both, although in both cases with a very low quality of evidence.
Criterion Validity
We identified only a single study
70
that assessed the criterion
validity of a shortened PROM (the Wound-QoL revised version)
compared with the original long version (the Wound-QoL). As
shown in Table 4, the results indicate that the evidence is suffi-
cient for this measurement property with moderate quality of
evidence.
Reliability
For all identified PROMs, except the QoL Instrument, the in-
ternal consistency of their scores was assessed. Nevertheless, we
could not interpret the criterion for good measurement properties
because none of these PROMs showed at least low evidence for
sufficient structural validity (see Table 4). Test-retest reliability of
scores was assessed in 6 identified PROMs (AOFAS-DFQ, CWIS,
DFS, DFS-SF, NeuroQoL, and Wound-QoL). We were only able to
pool the results of the CWIS and Wound-QoL studies. Regarding
DFS-SF, although this measurement property was assessed in 4
studies, only one study provided sufficient information to pool the
data (see Appendix Table 3 in Supplemental Materials found at
https://doi.org/10.1016/j.jval.2022.04.1737). For the remaining 3
PROMs, we found only one study for the AOFAS-DFQ and the
NeuroQoL, and for the DFS, not enough information was provided
to assess the criteria for good measurement properties. Only the
CWIS, the NeuroQoL, and the Wound-QoL showed sufficient evi-
dence for this measurement property, although of very low quality
for the first 2 and of low quality for the third (see Table 4).
10 VALUE IN HEALTH -2022

Measurement error was only assessed in 2 identified PROMs. In
the case of AOFAS-DFQ, we could not interpret it due to the lack of
information about minimal important change. Nevertheless, the
Wound-QoL showed sufficient evidence, albeit very low quality
(see Table 4).
Responsiveness
This measurement property was assessed in 5 PROMs. Onlythe
DFS-SF showed sufficient evidence with low quality for this
measurement property (see Table 4). The CWIS and the Wound-
QoL showed insufficient evidence given that ,75% of the hy-
potheses were confirmed.
Categorization of PROMs According to Suitability
Recommendations
We did not identify any instruments categorized as A. The DFS
and the DFS-SF were categorized as B. The remaining 8 PROMs
were categorized as C, 4 of which (CWIS, NeuroQoL, Norfolk QoL-
DN, and Wound-QoL) had better evidence forcontent validity than
the other 4 (see Table 4). Of these 4 PROMs, the Wound-QoL was
the most feasible (the lowest number of items and the shortest
completion time) (see Appendix Table 4 in Supplemental Mate-
rials found at https://doi.org/10.1016/j.jval.2022.04.1737).
Discussion
In this psychometric systematic review, we identified 10
available QoL PROMs for people affected by diabetic foot. The DFS
and the DFS-SF were the PROMs with a higher grade of evidence
for content validity. None of the PROMs identified provided suf-
ficient evidence for structural validity, so we could not interpret
the available evidence on internal consistency of their scores. Only
the NeuroQoL provided sufficient evidence for the hypotheses
testing for construct validity. Cross-cultural validity was examined
in the Wound-QoL and the Wound-QoL revised version. The CWIS,
the NeuroQoL, and the Wound-QoL showed sufficient evidence for
test-retest reliability of their scores. Measurement error of the
scores was assessed in 2 PROMs, but only the Wound-QoL could
be interpreted. The DFS-SF showed sufficient evidence for the
responsiveness of its scores. Therefore, available PROMs had
limited evidence for their measurement properties.
In comparison with an earlier review,
17
we found a larger
number of studies of some PROMs (CWIS and DFS-SF) and identi-
fied new ones such as the Wound-QoL and the Wound-QoL revised
version. According to the COSMIN guidelines, only PROMs with
sufficient content validity and at least a low quality of evidence for
sufficient internal consistency can be considered the most suitable
PROMs for use.
14-16
Structural validity is the starting point for
determining the quality of evidence for internal consistency.
14-16
Although all of the identified PROMs showed sufficient content
validity, none of them provided sufficient structural validity. Two
PROMs showed high-quality evidence for insufficient measurement
properties, the DFS for hypothesis testing and the DFS-SF for
structural validity and hypothesis testing. Consequently, their use
cannot be recommended until more evidence is developed. The
CWIS, the NeuroQoL, the Norfolk QoL-DN, and the Wound-QoL
could be potentially recommended for use until further evidence
is provided. Of these 4 instruments, the Wound-QoL is easier to
apply and would therefore be more clinical utility than the others.
Comprehensive database searches, the use of a rigorous and
up-to-date psychometric review methodology,
14-16
and the
systematic assessment of QoL condition-specific PROMs in a
large number of studies are the key strengths of this review.
Nevertheless, methodological quality scoring, interpretation of
results, and evidence grading remain subjective processes.
Therefore, the process of independent review and consensus
ratings helped to resolve discrepancies and reduce variability in
interpretation. In addition, psychometric reviews are quite
complex because they involve multiple reviews, one review for
each measurement property. Accordingly, the review team
included reviewers with knowledge of the construct of interest
and experience with the target population and with the field of
psychometrics and qualitative research. Finally, public and pa-
tient involvement in research, both in the field of wound care
and in general, is of increasing interest to researchers and cli-
nicians.
72,73
Hence, one possible approach to consider would be
to include people affected by diabetic foot as research partners
in future psychometric reviews for rating the content of the
identified PROMs.
Measuring the QoL of people affected by diabetic foot re-
quires robust PROMs that allow researchers and clinicians to
come as close as possible to the reality experienced by the
person. The COSMIN initiative provides useful tools
14-16 ,74
for
the development of studies aimed at providing more evidence
on available PROMs and for the design and evaluation of new
PROMs. Content validity is the most important measurement
property of a PROM.
16
Input from the target population of a
PROM is essential to assess the 3 aspects of this measurement
property: relevance, comprehensibility, and comprehensive-
ness.
16
To assess these aspects, it is necessary to use both
quantitative and qualitative methodologies. We found this to be
the weakest point of the development of identified PROMs,
especially the use of rigorous qualitative methodologies for
identifying and selecting instrument items. In contrast, a PROM’s
content validity may be different when used in different pop-
ulations or different contexts. Thus, each new use may require
new supporting evidence. Nevertheless, the methodological
quality of the content validity studies was mostly doubtful and
in some cases inadequate. Therefore, This is clearly a research
area that needs to be improved. Structural validity and cross-
cultural validity are aspects of construct validity. Information
on model fit indices was not available for 6 identified PROMs.
We found only 2 studies that analyzed the cross-cultural validity
of the identified PROMs despite the numerous adaptations and
translations that have been carried out. This type of validity is
essential to determine the equivalence of scores between the
original population and the new target population.
15
Most
studies used Pvalues to test hypotheses for construct validity or
responsiveness rather than to assess whether the magnitude of
correlations or observed differences were similar or greater than
expected. The expected differences or changes need to be
defined in advance, and the interpretation of the tests needs to
be based on their observed magnitude and direction and not
only on statistical criteria.
14-16
Test-retest reliability is a pre-
requisite for determining the potential use of a PROM to assess
trends or changes over time. We identified 17 studies that
evaluated this property. Nevertheless, only 2 of these studies
were rated with adequate methodological quality. The reasons
for this weakness in the quality of the studies were no evidence
provided that respondents were stable, use of inappropriate
time interval, and different test conditions in both assessments.
Therefore, future studies need to consider all these limitations to
provide better quality evidence.
-- 11

Table 4. Summary of findings for each patient-reported outcome measure according to the recommendation for use.
PROM Measurement property Summary results Overall rating Quality of evidence
Category A: PROMs whose content validity had sufficient evidence, and at least a low quality of evidence for a sufficient internal consistency of
its scores (recommended for use)
No PROMs categorized as “A”were found in this review
Category B: PROMs with high-quality evidence for an insufficient measurement property (unrecommended for use)
DFS Content validity NA Sufficient Moderate: PROM development
study doubtful quality, and
there is at least one content
validity study of doubtful
quality.
Structural validity Not all information for “1”
reported
Indeterminate NA
Internal consistency Criteria for “at least low
evidence for sufficient
structural validity”not met
Indeterminate NA
Reliability ICC or weighted Kappa not
reported
Indeterminate NA
Hypothesis testing 29 out of 39 (74%) hypotheses
confirmed
Insufficient High: there are multiple studies
of very good quality available.
Responsiveness No hypothesis defined Indeterminate No hypothesis defined
DFS-SF Content validity NA Sufficient Moderate: PROM development
study doubtful quality, and
there is at least one content
validity study of doubtful
quality
Structural validity 6 factors: CFI ranged from 0.84
to 0.94 and RMSEA ranged
from 0.06 to 0.10
Insufficient High: there are multiple studies
of very good quality available.
Internal consistency Criteria for “at least low
evidence for sufficient
structural validity”not met (?)
Indeterminate NA
Reliability ICC range 0.51-0.92;
inconsistent
Insufficient Low: there is one study of
adequate validity, and results
are inconsistent.
Hypothesis testing 17 of 27 (63%) hypotheses
confirmed
Insufficient High: there are multiple studies
of very good quality available.
Responsiveness 1 of 1 (100%) hypothesis
confirmed
Sufficient Low: there is one study of
doubtful quality available.
Category C: PROMs categorized not in A or B (recommended for use until further evidence is provided)
AOFAS-DFQ Content validity NA Sufficient Very low: PROM development
study inadequate quality, no
content validity studies, and
only part of the study
population consisted of
patients with the disease of
interest.
Internal consistency Criteria for “at least low
evidence for sufficient
structural validity”not met
Indeterminate NA
Reliability ICC range from 0.35 to 0.85;
total sample size = 57
Insufficient Very low: there is only one
study of inadequate quality
available, only part of the study
population consisted of
patients with the disease of
interest, and the sample size
was lower than 100.
Measurement error MIC not defined Indeterminate NA
Responsiveness No hypothesis defined Indeterminate NA
continued on next page
12 VALUE IN HEALTH -2022

Table 4. Continued
PROM Measurement property Summary results Overall rating Quality of evidence
CWIS Content validity NA Sufficient Low: PROM development study
doubtful quality, there is at
least one content validity study
of doubtful quality, and only
part of the study population
consisted of patients with the
disease of interest.
Structural validity 3 factors: CFI = 0.69 and
RMSEA = 0.09
Insufficient Low: there is only one study of
adequate quality, and only part
of the study population
consisted of patients with the
disease of interest.
Internal consistency Criteria for “at least low
evidence for sufficient
structural validity”not met (?)
Indeterminate NA
Reliability Everyday living subscale, ICC =
0.81 (95% CI 0.66-0.90), I
2
=
54.3%; social life subscale,
ICC = 0.74 (95% CI 0.62-0.83),
I
2
= 33.8%; and wellbeing
subscale, ICC = 0.69 (95% CI
0.48-0.82), I
2
= 54.4%; total
sample size = 283; inconsistent
Sufficient Very low: there are 2 studies of
doubtful quality available,
results are moderately
inconsistent, and only part of
the study population consisted
of patients with the disease of
interest.
Hypothesis testing 29 of 67 (43%) hypotheses
confirmed
Insufficient Moderate: there are multiple
studies of very good quality
available, and only part of the
study population consisted of
patients with the disease of
interest.
Responsiveness 3 of 5 (60%) hypothesis
confirmed
Insufficient Low: there is only one study of
doubtful quality available.
HRQLQDFU Content validity NA Sufficient Very low: PROM development
study inadequate quality and
no content validity studies
Internal consistency Criteria for “at least low
evidence for sufficient
structural validity”not met
Indeterminate NA
NeuroQoL Content validity NA Sufficient Low: PROM development study
doubtful quality, there is at
least one content validity study
of doubtful quality, and only
part of the study population
consisted of patients with the
disease of interest.
Structural validity Not all information for “1”
reported
Indeterminate NA
Internal consistency Criteria for “at least low
evidence for sufficient
structural validity”not met
Indeterminate NA
Reliability ICC range 0.76-0.90; total
sample size = 15
Sufficient Very low: there is only one
study of doubtful quality
available, and sample size was
lower than 50.
Hypothesis testing 7 of 9 (78%) hypotheses
confirmed
Sufficient Moderate: there is one study of
very good quality available, and
only part of the study
population consisted of
patients with the disease of
interest.
continued on next page
-- 13

Table 4. Continued
PROM Measurement property Summary results Overall rating Quality of evidence
Norfolk QoL-DN Content validity NA Sufficient Low: PROM development study
doubtful quality, there is at
least one content validity study
of doubtful quality, and only
part of the study population
consisted of patients with the
disease of interest.
Structural validity Not all information for “1”
reported
Indeterminate NA
Internal consistency Criteria for “at least low
evidence for sufficient
structural validity”not met
Indeterminate NA
Hypothesis testing 9 of 14 (64%) hypotheses
confirmed
Insufficient Moderate: there is one study of
very good quality available, and
only part of the study
population consisted of
patients with the disease of
interest.
Quality of life instrument Content validity NA Sufficient Very low: PROM development
study inadequate quality, no
content validity studies, and
only part of the study
population consisted of
patients with the disease of
interest.
Hypothesis testing 4 of 6 (67%) hypotheses
confirmed
Insufficient Very low: there is only one
study of doubtful quality
available, and only part of the
study population consisted of
patients with the disease of
interest.
Wound-QoL Content validity NA Sufficient Low: PROM development study
inadequate quality, there is at
least one content validity study
of doubtful quality, and only
part of the study population
consisted of patients with the
disease of interest.
Structural validity 3 factors: CFI ranged from 0.90
to 0.91 and RMSEA = 0.09
Insufficient Moderate: there are 2 studies
of very good quality available,
and only part of the study
population consisted of
patients with the disease of
interest.
Internal consistency Criteria for “at least low
evidence for sufficient
structural validity”not met
Indeterminate NA
Cross-cultural validity mCFA metric invariance across
different countries: CFI = 0.01
and RMSEA = 0.01
Sufficient Very low: there is only one
study of doubtful quality
available, and only part of the
study population consisted of
patients with the disease of
interest.
Reliability Total score, ICC = 0.87 (95% CI
0.84-0.90), I
2
= 0.0%; body
subscale, ICC = 0.80 (95% CI
0.63-0.89), I
2
= 11.7%; psyche
subscale, ICC = 0.81 (95% CI
0.73-0.87), I
2
= 0.0%; and
everyday life subscale, ICC =
0.82 (95% CI 0.80-0.84), I
2
=
0.0%; total sample size = 185;
consistent
Sufficient Low: there is only one study of
adequate quality available, and
only part of the study
population consisted of
patients with the disease of
interest.
continued on next page
14 VALUE IN HEALTH -2022

Conclusions
This review found no fully suitable condition-specificPROMto
measure QoL in people affected by diabetic foot. Pending further
evidence, 4 PROMs could be provisionally recommended for use.
Of these PROMs, Wound-QoL is the most feasible. These findings
suggest that, in general, there are important evidence gaps for the
measurement properties of QoL PROMs in people affected by
diabetic foot. Clinicians, researchers, healthcare decision makers,
and policy makers should be aware of these limitations before
using these PROMs for decision making. The present review
establishes a framework for future assessments of available
PROMs or for the design of new ones.
Supplemental Materials
Supplementary data associated with this article can be found in the
online version at https://doi.org/10.1016/j.jval.2022.04.1737.
Article and Author Information
Accepted for Publication: April 19, 2022
Table 4. Continued
PROM Measurement property Summary results Overall rating Quality of evidence
Measurement error SDC ,MIC in all scores except
in psyche subscale
Sufficient Very low: there is only one
study of doubtful quality
available, and only part of the
study population consisted of
patients with the disease of
interest.
Hypothesis testing 39 of 72 (54%) hypotheses
confirmed
Insufficient Moderate: there are multiple
studies of very good quality
available, and only part of the
study population consisted of
patients with the disease of
interest.
Responsiveness 12 of 25 (48%) hypotheses
confirmed
Insufficient Moderate: there are multiple
studies of very good quality
available, and only part of the
study population consisted of
patients with the disease of
interest.
Wound-QoL revised version Content validity NA Sufficient Very low: PROM development
study inadequate quality, no
content validity studies and
only part of the study
population consisted of
patients with the disease of
interest.
Structural validity 3 factors: CFI = 0.94 and
RMSEA = 0.08
Insufficient Moderate: there is one study of
very good quality available, and
only part of the study
population consisted of
patients with the disease of
interest.
Internal consistency Criteria for “at least low
evidence for sufficient
structural validity”not met
Indeterminate NA
Cross-cultural validity mCFA metric invariance across
different countries, continent
origin, age, sex, and wound
type. All analyses showed CFI ,
0.02 and RMSEA ,0.015
Sufficient Very low: there is only one
study of doubtful quality
available, and only part of the
study population consisted of
patients with the disease of
interest.
Criterion validity 4 of 4 (100%) hypotheses
confirmed
Sufficient Moderate: there is one study of
very good quality available, and
only part of the study
population consisted of
patients with the disease of
interest.
AOFAS-DFQ indicates American Orthopaedic Foot and Ankle Society Diabetic Foot Questionnaire; CFI, comparative fit index; CI, confidence interval; CWIS, Cardiff Wound
Impact Schedule/Scale; DFS, diabetic foot ulcer scale; DFS-SF, Diabetic Foot Ulcer Scale-Short Form; HRQLQDFU, Health-Related Quality of Life Questionnaire in Diabetic
Foot; ICC, intraclass correlation coefficient; mCFA, multilevel confirmatory factor analysis; MIC, minimal important change; NA, not applicable; NeuroQoL, Neuropathy-
and Foot Ulcer-Specific Quality of Life; Norfolk QoL-DN, Norfolk Quality of Life-Diabetic Neuropathy; PROM, patient-reported outcomes measure; RMSEA, root mean
square error of approximation; SDC, smallest detectable change.
-- 15

Published Online: xxxx
doi: https://doi.org/10.1016/j.jval.2022.04.1737
Author Affiliations: Nursing Department, Faculty of Nursing, Universitat
de Girona, Girona, Spain (Romero-Collado, Zabaleta-del-Olmo); Sant Pau
Nursing School University, Barcelona, Spain (Hernández-Martínez-Esparza,
Santesmases-Masana); Fundació Institut Universitari per a la recerca a
l’Atenció Primària de Salut Jordi Gol i Gurina (IDIAPJGol), Barcelona, Spain
(Zabaleta-del-Olmo); Gerència Territorial de Barcelona, Institut Català de la
Salut, Barcelona, Spain (Zabaleta-del-Olmo, Urpí-Fernández).
Correspondence: Edurne Zabaleta-del-Olmo, PhD, Gran Via Corts Cata-
lanes, 587 àtic, 08007 Barcelona, Spain. Email: ezabaleta@idiapjgol.org
Author Contributions: Concept and design:Romero-Collado, Zabaleta-del-
Olmo
Acquisition of data: Romero-Collado, Hernández-Martínez-Esparza,
Zabaleta-del-Olmo, Urpí-Fernández, Santesmases-Masana
Analysis and interpretation of data: Romero-Collado, Hernández-Martínez-
Esparza, Zabaleta-del-Olmo, Urpí-Fernández, Santesmases-Masana
Drafting of the manuscript: Zabaleta-del-Olmo
Critical revision of the paper for important intellectual content: Romero-
Collado, Hernández-Martínez-Esparza, Zabaleta-del-Olmo, Urpí-Fernán-
dez, Santesmases-Masana
Statistical analysis: Zabaleta-del-Olmo
Administrative, technical, or logistic support: Romero-Collado, Hernández-
Martínez-Esparza, Zabaleta-del-Olmo, Urpí-Fernández, Santesmases-
Masana
Supervision: Romero-Collado, Hernández-Martínez-Esparza, Zabaleta-del-
Olmo, Urpí-Fernández, Santesmases-Masana
Conflict of Interest Disclosures: The authors reported no conflicts of
interest.
Funding/Support: The authors received no financial support for this
research.
Acknowledgment: The authors appreciate the review of the English text
by P. Bialoskorski, MA. Open Access funding provided thanks to the CRUE-
CSIC agreement with Elsevier.
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