Validation of a manual ability questionnaire in patients with systemic sclerosis

Article (PDF Available)inArthritis & Rheumatology 61(5):695-703 · May 2009with43 Reads
DOI: 10.1002/art.24426 · Source: PubMed
Abstract
To adapt and validate a manual ability questionnaire, the ABILHAND, developed through the Rasch methodology in patients with systemic sclerosis (SSc). The original version of the ABILHAND, which includes 81 manual daily activities, was presented to 156 patients with SSc. They were asked to provide their perceived difficulty in performing each manual activity on a 3-level scale: impossible, difficult, or easy. Items were selected from well-established psychometric criteria. The patients were reassessed 1 month later to test the reproducibility. Concomitantly, they were clinically evaluated for their disease activity/severity, and their functional ability was tested with the Health Assessment Questionnaire (HAQ). The 26 selected items defined a unidimensional and linear measure of manual ability and showed a continuous progression in their difficulty. The item difficulty hierarchy was invariant across 12 patient-related factors and the manual ability score was reproducible over time. Finally, the manual ability was significantly poorer in SSc patients with more severe disease, and was negatively correlated with the HAQ score (rho = -0.733). The SSc-adapted ABILHAND questionnaire is a reliable, valid, reproducible, linear, and unidimensional measure to assess and followup on the manual ability of patients with SSc; therefore, it could become a useful additional tool in clinical trials to assess treatment efficacy.
Validation of a Manual Ability Questionnaire in
Patients With Systemic Sclerosis
MARIE VANTHUYNE,
1
VANESSA SMITH,
2
SEHER ARAT,
3
RENE
´
WESTHOVENS,
3
FILIP DE KEYSER,
2
FRE
´
DE
´
RIC A. HOUSSIAU,
1
JEAN-LOUIS THONNARD,
1
AND LAURE VANDERVELDE
1
Objective. To adapt and validate a manual ability questionnaire, the ABILHAND, developed through the Rasch meth-
odology in patients with systemic sclerosis (SSc).
Methods. The original version of the ABILHAND, which includes 81 manual daily activities, was presented to 156
patients with SSc. They were asked to provide their perceived difficulty in performing each manual activity on a 3-level
scale: impossible, difficult, or easy. Items were selected from well-established psychometric criteria. The patients were
reassessed 1 month later to test the reproducibility. Concomitantly, they were clinically evaluated for their disease
activity/severity, and their functional ability was tested with the Health Assessment Questionnaire (HAQ).
Results. The 26 selected items defined a unidimensional and linear measure of manual ability and showed a continuous
progression in their difficulty. The item difficulty hierarchy was invariant across 12 patient-related factors and the
manual ability score was reproducible over time. Finally, the manual ability was significantly poorer in SSc patients with
more severe disease, and was negatively correlated with the HAQ score (
ⴝⴚ0.733).
Conclusion. The SSc-adapted ABILHAND questionnaire is a reliable, valid, reproducible, linear, and unidimensional
measure to assess and followup on the manual ability of patients with SSc; therefore, it could become a useful additional
tool in clinical trials to assess treatment efficacy.
INTRODUCTION
Systemic sclerosis (SSc) is a life-threatening multisystemic
disease purportedly resulting from the combination of 3
types of injuries: autoimmune, vascular, and fibrotic. Ac-
tivation of the immune system leads to the production of
SSc-specific autoantibodies, vascular damage causes the
progressive obstruction of small- and medium-sized arter-
ies, and excessive collagen deposition is responsible for
skin and internal organ fibrosis (1).
Several disease manifestations may contribute to man-
ual disability in patients with SSc, such as sclerodactyly,
scleroedema, Raynaud’s phenomenon, digital ulcers, fin-
ger calcinosis, and arthritis. Manual ability may be defined
as the capacity to manage daily activities requiring the
use of the upper extremities, independent of the strategy
involved (2). Manual ability can be inferred from the pa-
tients’ perceived difficulty in performing activities, as de-
termined by other questionnaires such as the Duruo¨z Hand
Index (3) or the UK Scleroderma Functional Score (4). The
former, although tested in patients with SSc (5), was not
specifically designed, nor adapted, for SSc.
The ABILHAND questionnaire, developed using the
Rasch model (2), offers the advantage of selecting and
hierarchizing manual activities that patients with different
diseases find specifically difficult to realize. It has been
validated in patients with chronic stroke (6) or with rheu-
matoid arthritis (RA) (7), and in children with cerebral
palsy (8). The aim of this study is to adapt and validate the
ABILHAND questionnaire as a measure of manual ability
in patients with SSc.
Supported by unrestricted research grants from the
Socie´te´ Royale Belge de Rhumatologie/Koninklijke Bel-
gische Vereniging voor Reumatologie, the Fonds pour la
Recherche Scientifique en Rhumatologie/Fonds voor Weten-
schappelijk Reuma Onderzoek, and the Association des Pa-
tients Scle´rodermiques de Belgique. Dr. Vanthuyne’s work
was supported by a research fellowship from the Fonds
National de la Recherche Scientifique, Belgium. Dr. Vander-
velde’s work was supported by a grant from the Fondation
Saint-Luc.
1
Marie Vanthuyne, MD, Fre´de´ric A. Houssiau, MD, PhD,
Jean-Louis Thonnard, PhD, Laure Vandervelde, PhD: Clin-
iques universitaires Saint-Luc, Universite´ catholique de
Louvain, Brussels, Belgium;
2
Vanessa Smith, MD, Filip De
Keyser, MD, PhD: Ghent University, Ghent, Belgium;
3
Seher
Arat, RN, MSN, Rene´ Westhovens, MD, PhD: Katholieke
Universiteit Leuven, Leuven, Belgium.
Address correspondence to Marie Vanthuyne, MD, Univer-
site´ catholique de Louvain, Rheumatology Department, Clin-
iques universitaires Saint-Luc, Avenue Hippocrate, 10, B-1200
Brussels, Belgium. E-mail: marie.vanthuyne@uclouvain.be.
Submitted for publication September 11, 2008; accepted
in revised form January 1, 2009.
Arthritis & Rheumatism (Arthritis Care & Research)
Vol. 61, No. 5, May 15, 2009, pp 695–703
DOI 10.1002/art.24426
© 2009, American College of Rheumatology
ORIGINAL ARTICLE
695
PATIENTS AND METHODS
Patients. In March 2008, 218 patients fulfilling LeRoy
and Medsger’s classification criteria for SSc (9) and in-
cluded in the Belgian Systemic Sclerosis Cohort by 3 uni-
versity hospitals were asked, in their own language, to
answer a manual ability questionnaire. One hundred fifty-
six patients with SSc (89 Dutch speakers and 67 French
speakers) agreed to participate. According to Leroy’s clas-
sification, 19 patients with limited SSc (lSSc), 104 patients
with limited cutaneous SSc (lcSSc), and 33 patients with
diffuse cutaneous SSc (dcSSc) composed the sample.
Patients were also asked to fill in the Health Assessment
Questionnaire (HAQ; score ranging from 0 no disability
to 3 impossible to do) (10) and 2 visual analog scales
(VAS; ranging from 0 mm no limitation to 100 mm
maximal limitation) about the interference of Raynaud’s
phenomenon and of digital ulcers with their daily activi-
ties. We checked for the presence of digital ulcers and
digital pitting scars. We measured the Rodnan modified
total skin score (TSS; range 0 –51) (11) and the fingertip
to palm distance in flexion (distance between the tip of
the third finger and the distal palmar crease; most affected
side selected). Finally, we computed the Scleroderma
Disease Activity Score (DAS; range 0–10) (12) and the
disease severity score (range 0 4 for each of the 9 organ
systems, therefore the total disease severity score ranges
from 0 –36) (13).
The clinical and functional characteristics of the 156
patients are described in Table 1. There was no significant
difference in the clinical characteristics (sex, age, disease
subsets, and TSS) of the patients who did not respond to
the questionnaire (62 of 218) compared with those who
did respond.
Manual ability assessment. Manual ability was as-
sessed with the ABILHAND questionnaire (2), which
evaluates the difficulties a patient may experience in
performing manual activities of daily living. In a prelimi-
nary study, 10 patients with lcSSc and 10 patients with
dcSSc, the most regularly followed patients with that dis-
ease subset consecutively examined in the outpatient de-
partment, were asked to propose other relevant manual
activities not included in the original 56-item set. Follow-
ing the patients’ suggestions, 25 items were added to the
original set, and the experimental version of ABILHAND
questionnaire consisted of 81 items. The patients were
asked to provide their perceived difficulty in performing
each of the 81 activities using a 3-level scale, where 0
impossible, 1 difficult, and 2 easy. Each activity could
be completed irrespective of the arm(s) used, and indepen-
dent of the adaptive strategies. Activities not commonly
performed in the previous 3 months were not scored, and
were recorded as missing responses (6.4%). The items
were randomly presented to avoid any item order bias.
Data analysis: measuring manual ability through the
Rasch model. The data were analyzed with the Rasch
Unidimensional Measurement Models computer program
(RUMM2020; RUMM Laboratory, Perth, Western Austra-
lia). The Rasch model estimates the item difficulty and the
patient manual ability on a common linear scale from the
responses given to each item within a probabilistic frame-
work (14). This model is used to investigate response
category functioning, item and patient fit to the model,
scale unidimensionality, item local independence, patient
targeting, and scale reliability (15).
The category functioning is studied by verifying that
successive response categories for each item represent in-
creasing levels of ability, and that thresholds between
adjacent categories are located in the expected order. The
thresholds correspond to the manual ability required to
have a higher probability to select one category rather
than the previous one. The Rasch model could verify, via
a likelihood ratio test, whether the response categories
share the same discrimination across all items. This allows
the use of a rating scale model (16,17), thus making the
clinical interpretation of the scores easier. The overall item
and patient fit to the model is checked by testing how close
the observed data are from the model expectations. Indi-
vidual item fit indicates whether the item contributes to
Table 1. Characteristics of the patients (n 156)*
Sex, n (%)
Male 32 (20.5)
Female 124 (79.5)
Age, years 54.3 (21–82)
Language, n (%)
French 67 (42.9)
Dutch 89 (57.1)
SSc subsets, n (%)
lSSc 19 (12.2)
lcSSc 104 (66.7)
dcSSc 33 (21.1)
Disease duration, years† 9.7 (0.6–67.9)
Fingertip to palm distance in
flexion, mm‡
7 (0–55)
TSS score (range 0–51) 4 (0–25)
Presence of digital pitting
scars, n (%)
65 (41.7)
Presence of digital ulcers,
n (%)
21 (13.5)
HAQ score (range 0–3) 0.5 (0–2.875)
VAS score for Raynaud’s
phenomenon, mm
26 (0–100)
VAS score for digital ulcers,
mm
3 (0–100)
Presence of calcinosis on
hands radiograph, n (%)
27 (17.3)
Presence of osteolysis on
hands radiograph, n (%)
21 (13.5)
DAS (range 0–10) 1 (0–10)
Peripheral vascular DSS
(range 0–4)
1 (0–3)
Total DSS (range 0–36) 5 (0–15)
* Values are the median (range) unless otherwise noted. SSc
systemic sclerosis; lSSc limited SSc; lcSSc limited cutaneous
SSc; dcSSc diffuse cutaneous SSc; TSS Rodnan modified total
skin score; HAQ Health Assessment Questionnaire; VAS visual
analog scale; DAS Disease Activity Score; DSS disease severity
score.
Since onset of Raynaud’s phenomenon.
Distance between the tip of the third finger and the distal palmar
crease, most affected side selected.
696 Vanthuyne et al
the definition of the unidimensional manual ability con-
struct (18).
To test item unidimensionality, the sample is divided
along the variable into level groups called class intervals.
For each item, the degree of similitude between the ob-
served responses and the expected responses in each class
interval are computed through a standardized residual and
a chi-square fit statistic reported by the software (19). The
item standardized residual corresponds to the sum of the
differences between the observed and expected scores for
each patient, divided by the SD of the differences, and is
sensitive to item discrimination. Positive and negative val-
ues represent an under discrimination and an over dis-
crimination of the item, respectively. The chi-square fit
statistic represents the deviations from the model expec-
tations.
The assumption of local independency and, subse-
quently, the scale unidimensionality is verified by a prin-
cipal component analysis of the residuals (20). The corre-
lation between items and the first residual factor could
define 2 subsets of items (i.e., the positively and the neg-
atively correlated items). Two separate patients’ locations
are estimated from these subsets of items, and are com-
pared using a t-test (20). The targeting is checked by com-
paring the mean patient location with the mean item dif-
ficulty. The software also reports the reliability, indicating
the level of measurement precision attained.
Item selection. Starting with the 81 experimental items,
successive analyses were performed to select the items
composing the final ABILHAND scale. The following cri-
teria were used (7): 1) a response rate 80%, indicating
that the activity is commonly performed by patients with
SSc; 2) a difficulty targeted at the level of the sample
ability, indicating that items provide enough information
to estimate the patients’ ability; 3) an ordered rating scale,
indicating that the 3 response categories are well discrim-
inated; 4) a discrimination of the 3 response categories
similar to the other items, verified by a nonsignificant
likelihood ratio test (21); 5) an adequate fit to the Rasch
model confirmed by P values (by chi-square) greater than
0.05 and standardized residuals between 2.5 and 2.5
(21), indicating that the items contribute to the definition
of the unidimensional construct of manual ability; and 6)
no redundancy in item location, preferably keeping items
that best fit the Rasch model.
Determining the scale invariance through differential
item functioning. The invariance of the item difficulty
hierarchy was checked according to 12 dichotomous pa-
tient-related factors: 1) sex (male versus female), 2) patient
age (median 54 years; 54 years versus 54 years), 3) lan-
guage community (Dutch speakers versus French speak-
ers), 4) SSc subsets (lcSSc versus dcSSc), 5) disease dura-
tion from the onset of Raynaud’s phenomenon (median 6.3
years; 6.3 years versus 6.3 years), 6) fingertip to palm
distance (median 7 mm; 7 mm versus 7 mm), 7) TSS
(median 4; 4 versus 4), 8) presence of digital pitting
scars (yes versus no), 9) presence of digital ulcers (yes
versus no), 10) functional ability (median HAQ score 0.5;
0.5 versus 0.5), 11) DAS (3 versus 3), and 12) total
disease severity score (median score 5; 5 versus 5).
When the patients’ numbers were unbalanced in the di-
chotomous subgroups (e.g., 124 women for 32 men), a
sample of the largest group equivalent to the smallest one
was randomly selected to avoid any bias due to the pa-
tients’ number in the item hierarchy estimate.
Scale test–retest reliability. The test–retest reliability of
the patients’ responses and of the item hierarchy estimate
was investigated by reassessing 134 patients with SSc 1
month after the first evaluation, and determined using
intraclass correlation coefficients (ICCs) (22).
Scale construct validity. The construct validity was
tested by examining the degree of association between
the patients’ ABILHAND measures and other measures
widely used in patients with SSc. Moreover, the rela-
tionships between these patients’ measures and demo-
graphic (age, sex, and language community) and clinical
(SSc subsets) indices were tested either by a correlation
coefficient for continuous indices or by a one-way ana-
lysis of variance for groups of nominal indices. The ana-
lyses were performed with SigmaStat software (SPSS,
Chicago, IL); P values less than 0.05 were considered sta-
tistically significant. For the multivariate analysis, the
combination of a multiple logistic regression, a multiple
correspondence analysis, and a discriminant analysis was
used to detect the manual ability’s predictors. Before per-
forming the multivariate analysis using dichotomous
variables, we checked whether they strongly correlated
with each other when expressed in continuous and in
dichotomous values. We found no strong relationship
(r 0.8) between any variables, thereby making colinearity
unlikely.
RESULTS
Refinement of the ABILHAND questionnaire for pa-
tients with SSc. Successive analyses through the Rasch
model removed 55 items from the original 81-item set.
Five items were not commonly performed by patients with
SSc (e.g., typewriting), 16 were too easy (e.g., turning on a
television set), none presented reversed thresholds, 20 had
a different discrimination of the response categories (e.g.,
sharpening a pencil), 5 did not contribute to the definition
of the unidimensional construct (e.g., grooming), and 9
were redundant. The final ABILHAND scale contains 26
daily manual activities specifically selected for patients
with SSc (Figure 1 and Table 2).
Psychometric qualities of ABILHAND in patients with
SSc. The likelihood ratio test performed on the 26 se-
lected items was not significant (P 0.16), allowing the
use of a rating scale model. The reported overall fit statis-
tics for the final scale were close to a standardized normal
distribution for item and person fit residuals (mean SD
0.301 0.845 and 0.324 1.105, respectively), and
the reported item-trait interaction was not significant
Manual Ability in Systemic Sclerosis 697
(
2
101.263, 130 df, P 0.97). The t-test between
the patients’ locations, estimated via the items positively
correlated with the first residual factor of the principal
component analysis on the residuals and those esti-
mated by the negatively correlated items, was not signifi-
cant (t 0.072, 136 df, P 0.943), indicating that the item
local independence and the scale unidimensionality are
assumed.
The calibration of the 26-item ABILHAND scale is pre-
sented in Table 2. The items are classified according to
decreasing difficulty from top to bottom (range 2.41 to
2.59 logits), with higher logit values representing more
difficult items. The manual ability measure is expressed
in logits (i.e., log-odds units), which is a linear unit de-
fined as the natural logarithm of the odds of successful
achievement by a patient for any item. This unit is con-
stant along the measurement scale, and the zero is set by
convention at the average difficulty of the whole selected
item set. The SE of the item difficulty estimates (mean
0.21, range 0.19 to 0.26), the standardized residuals (mean
0.30, range 1.59 to 1.95), the fit statistic computed as a
chi-square, and the associated P values are also shown in
Figure 1. Structure of the ABILHAND scale in patients with systemic sclerosis (SSc). Top:
distribution of manual ability measures of the 156 patients with SSc. Nineteen patients
(12%) with extreme scores could not be assessed by the scale because they scored all of the
activities as easy. Upper middle: a patient’s expected response for each item as a function of
the manual ability. Zero is, by convention, set at the average item difficulty; i.e., being able
to easily lace shoes requires a measure of 2.47 logits, and a patient with a measure below
1.77 would be unable to fully accomplish this. A patient with a measure of 0 logits would
be expected to perform the 2 easiest activities without difficulty, the average activities with
some difficulties, and would be unable to perform the 2 most difficult activities. Lower
middle: the Ogival relationship makes it possible to convert the ordinal raw score into a
linear measure of manual ability. The raw score ranges 0 –52 (from 26 items each scored
0–2). The manual ability in logits is an infinite measure. This relationship is quasi-linear in
its central part, but a unitary increment in total score encompasses larger differences at both
ends of the scale. Bottom: the scale graduations are represented by the 52 thresholds (2 per
item). The first graduation corresponds to the manual ability required to choose difficult
rather than impossible for spreading butter on a slice of bread, and the last one represents the
manual ability required to select easy rather than difficult for opening a screw-topped jar.
698 Vanthuyne et al
Table 2. The 26 items define a unidimensional scale of
manual ability in patients with SSc, because all the P
values are not significant. The reliability index of the final
scale is 0.97.
Description of the ABILHAND scale. The structure and
the targeting of the linear ABILHAND scale in patients
with SSc are shown in Figure 1. The measurement range
represented by the thresholds distribution (4.71 to 4.54
logits) is well targeted to the range of the patients’ abilities
(4.02 to 5.75 logits). Nevertheless, the overall mean pa-
tient location is equal to 1.79 logits, indicating that pa-
tients report moderate difficulties in performing manual
activities. Indeed, 19 patients (11 with lcSSc, 1 with dc-
SSc, and 7 with lSSc) with a manual ability 5.75 logits
reported they could perform all activities easily, and 96
patients with a manual ability 0.29 logits reported they
could achieve all activities easily or with some difficulty.
None reported they could not perform any of the 26 man-
ual activities.
Differential item functioning. The item hierarchy in-
variance of the 26 selected items was tested across 12
dichotomous subgroups of patients using the differential
item functioning plots represented in Figure 2. As most
of the manual activities lie within the 95% confidence
interval (95% CI) of the identity line, the item diffi-
culty tends to be consistently estimated across demo-
graphic and clinical subgroups of patients. There are
some exceptions identified by their label, as shown in
Table 2.
Test–retest reliability. The test–retest reliability of the
patients’ measures is shown in Figure 3 (right panel). Most
of the measures lie within the 95% CI of the identity line,
indicating that patients consistently estimate their manual
ability. Moreover, the ICC 0.96 for the patient measures.
The left panel shows the item difficulty hierarchy between
the first and the second assessment. No item lies outside
the 95% CI of the identity line, and the item estimates
ICC 0.98, indicating an excellent reproducibility of the
item hierarchy.
Construct validity. The manual ability measures were
significantly different across SSc subsets. A post hoc ana-
lysis showed 1) that patients with lSSc had a higher man-
ual ability (mean SD 4.10 2.5 logits) than patients with
lcSSc (mean SD 2.44 2.44 logits) and patients with
dcSSc (mean SD 1.17 2.47 logits), and 2) that patients
with lcSSc have a significantly higher manual ability than
patients with dcSSc. The ABILHAND measures were neg-
atively correlated with the following clinical and para-
clinical indices: disease duration (r ⫽⫺0.28; P 0.001),
fingertip to palm distance (r ⫽⫺0.39; P 0.001), TSS
Table 2. ABILHAND calibration for patients with systemic sclerosis (n 156)
Item
Difficulty,
logits
SE,
logits
Residual,
z
Fit,
2
*
P
a. Opening a screw-top jar 2.41 0.19 0.25 4.00 0.55
b. Threading a needle 2.20 0.19 0.56 1.63 0.90
c. Putting on a piece of jewelry 2.12 0.19 0.65 6.60 0.25
d. Winding up a wristwatch 1.85 0.20 0.66 5.22 0.39
e. Shelling hazelnuts 1.62 0.20 1.95 7.61 0.18
f. Taking the cap off a bottle 1.05 0.19 0.75 2.41 0.79
g. Peeling potatoes with a knife 0.80 0.19 0.03 2.43 0.79
h. Buttoning up trousers 0.71 0.19 1.53 2.47 0.78
i. Cutting one’s nails 0.56 0.19 0.50 1.64 0.90
j. Wiping windows 0.44 0.20 1.16 5.74 0.33
k. Lacing shoes 0.35 0.20 0.91 4.64 0.46
l. Cleaning vegetables 0.13 0.20 1.60 4.59 0.47
m. Peeling onions 0.05 0.20 0.12 6.13 0.29
n. Fastening a snap-fastener (e.g., bag,
jacket)
0.09 0.20 1.35 3.97 0.55
o. Fastening the zipper of a jacket 0.19 0.20 1.59 1.48 0.92
p. Tearing open a package of chips 0.22 0.21 0.12 3.96 0.56
q. Taking a coin out of a pocket 0.30 0.20 0.35 4.19 0.52
r. Handling scissors 0.43 0.20 0.00 1.46 0.92
s. Cutting meat 0.61 0.20 0.73 1.52 0.91
t. Unwrapping a chocolate bar 0.97 0.22 0.17 4.93 0.42
u. Handling a stapler 1.29 0.22 0.52 4.13 0.53
v. Turning off a tap 1.61 0.22 0.42 0.45 0.99
w. Putting cream on one’s body 1.79 0.23 0.72 4.49 0.48
x. Opening mail 1.88 0.24 0.67 8.88 0.11
y. Brushing one’s hair 2.31 0.26 0.49 2.82 0.73
z. Spreading butter on a slice of bread 2.59 0.26 0.78 3.88 0.57
* Degrees of freedom 5.
Manual Ability in Systemic Sclerosis 699
(
⫽⫺0.39; P 0.001), VAS dealing with the interfer-
ence of Raynaud’s phenomenon (
⫽⫺0.32; P 0.001),
DAS (
⫽⫺0.4; P 0.001), total disease severity score
(
⫽⫺0.53; P 0.001), and HAQ score (
⫽⫺0.73; P
0.001). No relationship was found between manual ability
and sex, language community, presence of digital pitting
scars, or the presence of calcinosis on hand radiographs.
The multivariate analysis indicates that a HAQ score 0.5
and a total disease severity score 5 were the only inde-
pendent predictors of a poor manual ability (Table 3).
DISCUSSION
This manuscript describes the validation of the ABILHAND
questionnaire in a large population of patients with SSc.
We applied the Rasch model, which allows one to hier-
archize items to create a linear scale, provided that they fit
the unidimensionality imposed by the model (14). In this
case, manual ability tasks have been classified according to
their difficulty after eliminating those influenced by fac-
tors other than the manual ability itself. The resulting 26
selected items define a unidimensional scale (all P 0.05;
Table 2) and allow the patient’s manual ability to be
estimated and followed up on a linear scale through a
self-administered, patient-friendly, non–time-consuming
questionnaire.
To identify the manual disabilities associated with SSc,
we expanded the original 56-item set with 25 additional
manual tasks considered to be difficult by 20 patients with
SSc in a preliminary survey. Of these 81 items, 26 were
retained by the Rasch analysis. These include unimanual
and bimanual activities, as well as tasks requiring strength
and dexterity. They encompass a large range of activities,
such as dressing, cooking, hygiene, working in an office,
and cleaning. Interestingly, and not surprisingly, 6 of the
26 final items were among the 25 suggested by patients
themselves. Thus, putting on a piece of jewelry, handling
scissors, or lacing shoes indeed requires exquisite digital
ability that can be reduced by the presence of digital ul-
cer(s). Wiping windows and putting cream on one’s body
might be affected by defective hand stretching due to skin
fibrosis. Finally, Raynaud’s phenomenon can compromise
one’s ability to clean vegetables in cold water.
The hierarchy of the 26 items is consistent with the type
of hand involvement observed in patients with SSc. More
difficult items require either manual strength (e.g., open-
ing a screw-top jar) or finger precision (e.g., threading a
needle), whereas the easiest involve rather gross manual
Figure 2. Invariance of the ABILHAND scale in subgroups of patients with systemic sclerosis. Each panel
shows the differential item functioning plot for dichotomous subgroups of patients, divided according to
12 splitting criteria. The most difficult items are plotted in the top/right part of each. The difficulties of
the items lying outside the solid lines (the 95% confidence interval of the ideal invariance) and identified
by their labels (as shown in Table 2) were differently estimated in both subgroups of patients. lcSSc
limited cutaneous systemic sclerosis; dcSSc diffuse cutaneous systemic sclerosis; disease duration
disease duration since onset of Raynaud’s phenomenon; FTP fingertip to palm distance in flexion
(distance between the tip of the third finger and the distal palmar crease; most affected side selected);
TSS Rodnan modified total skin score; HAQ Health Assessment Questionnaire; DAS Disease
Activity Score; Total DSS total disease severity score.
700 Vanthuyne et al
activities (e.g., putting cream on one’s body). When we
compare the retained items with those retained in patients
with RA (7), some activities were perceived differently in
terms of difficulty. For instance, threading a needle is more
difficult for patients with SSc than for patients with RA
because it involves greater fine digital dexterity (i.e., re-
quiring intact fingertips). On the other hand, activities
such as handling a stapler are more difficult for patients
with RA due to wrist and metacarpophalangeal joint in-
volvement. These observations indicate that the 26 items
correspond to appropriate activities that specifically assess
manual ability in patients with SSc.
The ABILHAND scale for patients with SSc presented a
good reliability index, indicating that more than 7 groups
of significantly different manual abilities can be distin-
guished in our sample (23). The 26 items are well tar-
geted to the patients’ abilities, covering a wide range of
functional abilities, despite the fact that 12% of the pa-
tients were able to easily complete all the activities. More-
over, the item hierarchy and the self-perceived manual
ability were consistently reassessed after 1 month (Figure
3), confirming the excellent test–retest reliability of the
ABILHAND questionnaire.
The overall fit statistics of the 26 items showed that
the observed data fit the expectations of the Rasch
model because the item and person fit residuals were close
to a normal distribution. The 26 items were also locally
independent because the t-test between patients’ loca-
tions was not significant (20). Moreover, the overall chi-
square statistic was not significant, reflecting invariance
Table 3. Multiple logistic regression: predictors of poor manual ability (logit <2.14)*
Variable P OR (95% CI)
Age 54 years 0.21 1.9 (0.7–5.5)
Disease duration 9.7 years 0.41 1.5 (0.6–4.1)
dSSc rather than lcSSc or lSSc 0.86 0.9 (0.3–3.1)
TSS 15 0.80 1.2 (0.2–6.7)
Fingertip to palm distance 7 mm 0.37 2.5 (0.3–18.0)
Presence of digital pitting scars 0.25 0.5 (0.1–1.7)
Presence of digital ulcers 0.60 1.6 (0.3–9.5)
HAQ 0.5 0.0006 8.3 (2.5–27.7)
Digital ulcers VAS score 3 mm 0.92 2.5 (0.8–7.4)
Raynaud’s phenomenon VAS score 26 mm 0.95 1.0 (0.3–3.0)
DAS 3 0.41 2.0 (0.4–9.8)
Vascular DSS 1 0.56 1.4 (0.4–4.5)
Total DSS 5 0.04 3.7 (1.1–13.0)
Calcinosis on hand radiograph 0.22 0.4 (0.1–1.8)
Osteolysis on hand radiograph 0.90 1.1 (0.2–6.4)
* Except for the TSS and DAS, cut offs were based on median values. OR odds ratio; 95% CI 95%
confidence interval. See Table 1 for additional definitions.
Figure 3. Test–retest reliability of the ABILHAND scale. A, item difficulty perceived
by patients with systemic sclerosis at the first and second assessment, and the 95%
confidence interval (95% CI) (solid line) of the ideal invariance. The most difficult
items are plotted in the top/right part of the figure. Items within the solid lines were
ranked with the same hierarchy between both assessments. B, manual ability self-
perceived by patients at the first and second assessment, and the 95% CI (solid lines)
of the ideal invariance. More able patients are plotted in the top/right part of the
figure. Patients’ measures (dots) lying within the solid lines have the same estimated
manual ability at the first and the second assessment. ICC intraclass correlation
coefficient.
Manual Ability in Systemic Sclerosis 701
of the item hierarchy across the variable (15). The dif-
ferential item functioning plots confirmed the invariance
of the item hierarchy across 12 dichotomous subgroups
of patients. First, this hierarchy did not vary across differ-
ent disease subsets, suggesting that the ABILHAND ques-
tionnaire can be used to assess manual ability across the
spectrum of patients with SSc. Nevertheless, before using
ABILHAND in other SSc populations, it would be impor-
tant to verify that patients’ responses to the 26 items fit to
the Rasch model. Second, the item difficulty hierarchy was
not influenced by disease activity, disease severity, global
physical ability, or digital joints’ limitation. There are,
however, some exceptions; for instance, 2 activities re-
quiring more manual strength (i.e., opening a screw-top jar
and shelling hazelnuts) were considered to be more diffi-
cult for women than for men (Figure 2).
Our data demonstrate a stringent correlation between
manual disability and disease severity; the latter is not
only assessed by musculoskeletal and skin involvements
(e.g., fingertip to palm distance, TSS, distal phalangeal
osteolysis) but also by global disease scores (e.g., DAS and
disease severity score). In this respect, it is worth stating
that the skin score has been correlated with major organ
involvement and survival (24). In a multivariate analysis,
of 15 covariates tested, only the combination of a total
disease severity score 5 and a HAQ score 0.5 was
predictive of a low manual ability.
The HAQ is a self-report measure that quantifies func-
tional ability in daily activities (10). It is commonly used
in SSc patient evaluation, and was previously shown to
correlate with disease subsets, TSS, the presence of tendon
friction rubs, joint pain, muscle weakness, and the finger-
tip to palm distance (25). In our study, however, even if the
univariate analysis indicated that ABILHAND measures
were highly correlated with HAQ, the HAQ variance ex-
plains only 50% of the manual ability variance. Those
results are not surprising because the HAQ was not de-
signed for SSc and only tests 7 activities dealing specifi-
cally with manual ability.
In 1997, Steen and Medsger partially bridged the HAQ’s
lack of disease specificity by adding 6 patient-assessed
VAS evaluating SSc organ system symptoms, namely dig-
ital ulcers, Raynaud’s phenomenon, pain, overall disease
severity, and gastrointestinal and pulmonary symptoms. It
was shown that the vascular VAS (ulcers and Raynaud’s)
was strongly correlated with the presence of digital pitting
scars, tip ulcers, and gangrene (26). Nevertheless, these
VAS do not specifically address manual ability.
Two other functional questionnaires have been used in
SSc. The UK Scleroderma Functional Score is a self-
completed questionnaire, developed to assess upper ex-
tremity function and muscle weakness caused by skin
tightness in patients with SSc (4). It comprises 11 items,
not specifically dealing with manual ability, each of which
are scored from 0 (able to perform) to 3 (impossible to
achieve). The items were, however, selected by physicians
and patients with SSc based on a consensus and not by a
stringent statistical approach as in ABILHAND. Neverthe-
less, Smyth et al (27) observed a strong correlation be-
tween the UK Scleroderma Functional Score and the HAQ
in a group of 115 patients with SSc, a rather expected
finding because 5 of the 11 items of the UK Scleroderma
Functional Score are part of the HAQ.
The Duruo¨ z Hand Index (also called Cochin scale and
Hand Functional Disability Scale) is an 18-item question-
naire dealing with manual ability, initially designed for
patients with RA (28), then applied in osteoarthritis (29)
and 2 small groups of patients with SSc (3,5). The mean
Duruo¨z Hand Index score was significantly higher in pa-
tients with dcSSc compared with patients with lcSSc,
and was found to correlate with the HAQ. The major
difficulty with this questionnaire stems from its 6 response
levels, ranging from possible without difficulty to impos-
sible to do. In previous studies, patients were unable to
discriminate between more than 4 response levels (2), a
finding further confirmed by a statistical analysis demon-
strating that a 3 response level questionnaire was ideal (6).
In this respect, the 3 levels of answers (impossible, diffi-
cult, or easy) used in the ABILHAND questionnaire are
easily distinguished from each other by patients, a result
confirmed here because no item presented reversed thresh-
olds. Unlike ABILHAND, neither the UK Scleroderma
Functional Score nor the Duruo¨z Hand Index display the
fundamental qualities of measurement, such as linearity
and unidimensionality.
Taken together, we propose the use of a new question-
naire to assess manual ability in patients with SSc. The
questionnaire has been developed and validated using the
gold standard Rasch methodology in a large and clinically
well-studied group of patients with SSc. The linearity of
the scale, together with the invariance of the item hier-
archy, allows reliable assessment and reassessment of a
SSc patient’s manual ability. ABILHAND could therefore
contribute to the evaluation of the effects of new therapies.
Scoring sheets and instructions for ABILHAND are
available online at www.rehab-scales.org. Moreover, on-
line analyses taking into account the missing values will
directly convert raw scores into linear measures of manual
ability.
AUTHOR CONTRIBUTIONS
All authors were involved in drafting the article or revising it
critically for important intellectual content, and all authors ap-
proved the final version to be submitted for publication. Dr. Van-
thuyne had full access to all of the data in the study and takes
responsibility for the integrity of the data and the accuracy of the
data analysis.
Study conception and design. Vanthuyne, Smith, Arat, Westhovens,
De Keyser, Houssiau, Thonnard, Vandervelde.
Acquisition of data. Vanthuyne, Smith, Arat, Westhovens, De
Keyser, Houssiau, Thonnard, Vandervelde.
Analysis and interpretation of data. Vanthuyne, Smith, Arat,
Westhovens, De Keyser, Houssiau, Thonnard, Vandervelde.
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Manual Ability in Systemic Sclerosis 703
    • "Outcome measures of overall physical functioning and quality of life were most frequently being analysed. To a lesser extent, studies applied IRT to PRO measures of specific functioning [27,293031323334353637, pain [35,383940414243 , psychological constructs444546, and work disability4748495051. Studies also applied IRT to CMs such as measures of disease activity525354 and disease damage or radiographic severity555657. "
    [Show abstract] [Hide abstract] ABSTRACT: Background Although item response theory (IRT) appears to be increasingly used within health care research in general, a comprehensive overview of the frequency and characteristics of IRT analyses within the rheumatic field is lacking. An overview of the use and application of IRT in rheumatology to date may give insight into future research directions and highlight new possibilities for the improvement of outcome assessment in rheumatic conditions. Therefore, this study systematically reviewed the application of IRT to patient-reported and clinical outcome measures in rheumatology. Methods Literature searches in PubMed, Scopus and Web of Science resulted in 99 original English-language articles which used some form of IRT-based analysis of patient-reported or clinical outcome data in patients with a rheumatic condition. Both general study information and IRT-specific information were assessed. Results Most studies used Rasch modeling for developing or evaluating new or existing patient-reported outcomes in rheumatoid arthritis or osteoarthritis patients. Outcomes of principle interest were physical functioning and quality of life. Since the last decade, IRT has also been applied to clinical measures more frequently. IRT was mostly used for evaluating model fit, unidimensionality and differential item functioning, the distribution of items and persons along the underlying scale, and reliability. Less frequently used IRT applications were the evaluation of local independence, the threshold ordering of items, and the measurement precision along the scale. Conclusion IRT applications have markedly increased within rheumatology over the past decades. To date, IRT has primarily been applied to patient-reported outcomes, however, applications to clinical measures are gaining interest. Useful IRT applications not yet widely used within rheumatology include the cross-calibration of instrument scores and the development of computerized adaptive tests which may reduce the measurement burden for both the patient and the clinician. Also, the measurement precision of outcome measures along the scale was only evaluated occasionally. Performed IRT analyses should be adequately explained, justified, and reported. A global consensus about uniform guidelines should be reached concerning the minimum number of assumptions which should be met and best ways of testing these assumptions, in order to stimulate the quality appraisal of performed IRT analyses.
    Full-text · Article · Oct 2012
    • "Curiously enough, further research evolved toward again 'tailoring' the instrument to specific classes of patients. This was the case for: children versus adults (ABILHAND-Kids, 21 items of which only 11 are shared by the AH-ST 23–3 , Arnould et al., 2004 ); upper limb amputees, (ABILHAND- ULA 1.0, 22 items of the original 46, of which 11 are shared by the AH-ST 23–3 , with four levels; Burger et al., 2009); systemic sclerosis (SSc-adapted ABILHAND, 26 items of the original 46, of which 15 are shared by the AH- ST 23–3 ,with three levels; Vanthuyne et al., 2009); a revised version for rheumatoid arthritis (a 27 items of the original 46, of which 14 are shared by the AH-ST 23–3 , on three levels, Durez et al., 2007 ), and a 'neuromuscular' ageindependent version (22 items, 11 of which are shared by the AH-ST 23–3 , Vandervelde et al., 2010). This heralds the arrival of numerous new versions, specific to a variety of clinical conditions. "
    [Show abstract] [Hide abstract] ABSTRACT: ABILHAND is, in its original version, a 46-item, 4-level questionnaire. It measures the difficulty perceived by patients with rheumatoid arthritis as they do various daily manual tasks. ABILHAND was originally built through Rasch analysis. In a later study, it was simplified to a generic 23-item, three-level questionnaire, showing both cross-cultural (Belgium vs. Italy) and cross-impairment (rheumatoid arthritis vs. stroke) validity. Later research returned to the development of impairment-specific versions, with modified item sets and levels. Each version has its own Rasch-derived item difficulty calibrations, which are required to extract the patient's measure from the individual string of responses, through computerized algorithms. All of these hamper the practical application of the scale in rehabilitation units, where patients with diverse conditions may share similar impairments and treatment approaches. In this study through Rasch analysis the 'generic' scale was applied to 126 chronic patients with different upper limb impairments, and to 24 healthy controls. It was supported that the generic questionnaire remains valid across a variety of motor impairments. To further facilitate clinical application, a normative cut-off (>79 of 100) is suggested. Rasch-based item calibrations are provided together with a software routine designed to calculate, on individual patients, linear 0-100 measures and error estimates from the raw scores.
    Full-text · Article · Mar 2011
  • [Show abstract] [Hide abstract] ABSTRACT: Neuromuscular disorders (NMDs) can lead to specific manual disabilities due to hand muscle weakness and atrophy, myotonia or loss of sensory function. The aim of this study was to adapt and validate the ABILHAND questionnaire in children and adults with NMDs using the Rasch model. This questionnaire contained specific manual activities for children and for adults, as well as common manual activities. 124 adult patients and the parents of 124 paediatric patients were asked to provide their perceived difficulty in performing each manual activity on a three level scale: impossible (0), difficult (1) or easy (2). Items were selected from well established psychometric criteria (ordered categories, equal item discrimination, adequate fit to the Rasch model, lack of redundancy) using the Rasch Unidimensional Measurement Models (RUMM2020) computer programme. The 22 selected items contain four children specific items, four adult specific items and 14 items commonly applicable to both children and adults. They define a unidimensional and linear measure of manual ability and demonstrate continuous progression in their difficulty. The item hierarchy of difficulty was invariant across six patient related factors. The scale exhibited good precision (r=0.95) and the 22 items were well targeted to the patients' locations. The ABILHAND measures were strongly related to the ACTIVLIM measures (r=0.76) and poorly related to grip strength (r=0.36 for the right hand and r=0.40 for the left hand). This scale can be used for adults and children, allowing manual ability to be assessed from childhood to adulthood.
    Full-text · Article · Oct 2009
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