Reliability and validity of an adapted Thai version of the Scoliosis Research Society-22 questionnaire.

Abstract

The Scoliosis Research Society-22 (SRS-22) questionnaire is a widely accepted questionnaire used to assess the health-related quality of life for scoliosis patients in the United States. However, its adaptation in other languages is necessary for its multinational use. A cross-sectional study was performed to evaluate the validity and reliability of an adapted Thai version of the SRS-22 questionnaire.
An expert committee performed translation/retranslation of the English version of the SRS-22 questionnaire, as well as a cross-cultural adaptation process. Later, SRS-22 questionnaires and previously validated Short Form-36 version 2 (SF-36v2) outcome instruments were given to patients treated for idiopathic scoliosis with a minimum of 1 year of follow-up. Internal consistency and reproducibility were determined by Cronbach's alpha statistics and the intraclass correlation coefficient, respectively. Concurrent validity was measured by comparing SRS-22 results with a previously validated questionnaire (SF-36v2). Measurement was made using the Pearson correlation coefficient (r).
The study showed satisfactory internal consistency with Cronbach's alpha values for all of the corresponding domains (pain, 0.72; self-image/appearance, 0.87; mental health, 0.83; satisfaction with management, 0.63; and function/activity, 0.83). The test-retest reproducibility was also excellent or good for all domains (pain, 0.72; self-image/appearance, 0.85; mental health, 0.82; satisfaction, 0.62; and function/activity, 0.81). For concurrent validity, excellent correlation was found in two domains, good in six domains, moderate in five domains, and poor in five domains of the 18 relevant domains.
The Thai version of the SRS-22 outcome instrument has satisfactory internal consistency, excellent reproducibility, and acceptable validity.

Full text

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ORIGINAL CLINICAL ARTICLE
Reliability and validity of an adapted Thai version
of the Scoliosis Research Society-22 questionnaire
Pittavat Leelapattana•Gun Keorochana•
Jared Johnson•Wiwat Wajanavisit•
Wichien Laohacharoensombat
Received: 24 March 2010/Accepted: 23 November 2010/Published online: 12 December 2010
? The Author(s) 2010. This article is published with open access at Springerlink.com
Abstract
Purpose
questionnaire is a widely accepted questionnaire used to
assess the health-related quality of life for scoliosis patients
in the United States. However, its adaptation in other
languages is necessary for its multinational use. A cross-
sectional study was performed to evaluate the validity and
reliability of an adapted Thai version of the SRS-22
questionnaire.
Methods
An expert committee performed translation/
retranslation of the English version of the SRS-22 ques-
tionnaire, as well as a cross-cultural adaptation process.
Later, SRS-22 questionnaires and previously validated
Short Form-36 version 2 (SF-36v2) outcome instruments
were given to patients treated for idiopathic scoliosis with a
minimum of 1 year of follow-up. Internal consistency and
reproducibility were determined by Cronbach’s alpha sta-
tistics and the intraclass correlation coefficient, respec-
tively. Concurrent validity was measured by comparing
SRS-22 results with a previously validated questionnaire
(SF-36v2). Measurement was made using the Pearson
correlation coefficient (r).
Results
The study showed satisfactory internal consis-
tency with Cronbach’s alpha values for all of the
corresponding domains (pain, 0.72; self-image/appearance,
The Scoliosis Research Society-22 (SRS-22)
0.87; mental health, 0.83; satisfaction with management,
0.63; and function/activity, 0.83). The test–retest repro-
ducibility was also excellent or good for all domains (pain,
0.72; self-image/appearance, 0.85; mental health, 0.82;
satisfaction, 0.62; and function/activity, 0.81). For con-
current validity, excellent correlation was found in two
domains, good in six domains, moderate in five domains,
and poor in five domains of the 18 relevant domains.
Conclusions
The Thai version of the SRS-22 outcome
instrument has satisfactory internal consistency, excellent
reproducibility, and acceptable validity.
Keywords
Questionnaire ? Outcome ? SRS-22
Idiopathic scoliosis ? Thai adaptation ?
Introduction
Idiopathic scoliosis is the most common type of back
deformity [1]. Although it does not result in death, it
usually interferes with the quality of life of the patient. The
goal of the treatment for these patients is to improve the
deformity and prevent further progression of the curve.
These outcomes improve the quality of life of these
patients. In the past, we evaluated the outcomes by mea-
suring the corrected curve both clinically and on radio-
graphic film, but did not measure its effect on the patient’s
physical and mental well-being and quality of life [2, 3].
The Scoliosis Research Society-22 (SRS-22) questionnaire
addresses the patient’s perception of their medical condi-
tion and self-image, and its development has allowed us to
effectively evaluate the impact of treatment on quality of
life. The strengths of this questionnaire are the simplicity
of the questions, its specificity to idiopathic scoliotic
patients, and its reliability and concurrent validity. This
P. Leelapattana ? G. Keorochana (&) ? W. Wajanavisit ?
W. Laohacharoensombat
Department of Orthopaedics, Spine Unit,
Ramathibodi Hospital, Mahidol University,
Rama 6 Road, Ratchathewi, Bangkok 10400, Thailand
e-mail: gun_keo@yahoo.com
G. Keorochana ? J. Johnson
Department of Orthopaedic Surgery, UCLA Comprehensive
Spine Center, Santa Monica, CA 90404, USA
123
J Child Orthop (2011) 5:35–40
DOI 10.1007/s11832-010-0312-4

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questionnaire was invented by Haher et al. [4] and then
improved by Asher et al. [5–7] into the English version. It
is widely used in the English-speaking countries. It has also
been translated into many other languages, such as Turkish
[8], Spanish [9], and Chinese [10] versions. As Thai people
are culturally distinct, it is important to adapt and translate
the SRS-22 questionnaire into Thai and to validate it before
its use.
The purpose of this study was to assess the Thai version
of the SRS-22 and to determine its reliability and concur-
rent validity.
Materials and methods
The study was performed according to the recommended
protocol issued by the American Association of Orthopedic
Surgeon (AAOS) outcomes committee and as outlined by
Beaton et al. [11]. Firstly, the English version of the SRS-
22 questionnaire was translated independently into Thai by
two bilingual translators whose native tongue was Thai.
After comparing the two translations, the different points
were identified and resolved by consensus. Two native
English speakers who were also fluent in Thai then
retranslated this Thai version into English. The expert
committee, which was composed of two spine surgeons
(WL, WW), four translators, and two researchers (PL, GK),
further assessed the forward and back translations, and then
a consensus was achieved on the final translation.
The research ethics committee of our institute approved
this study and informed consent was obtained from all
participants. Two surveys, one for evaluating the validity
and the other for evaluating the reliability, were carried
out at a single center, the Spine Unit of Ramathibodi
Hospital. We included all patients who were diagnosed
with idiopathic scoliosis treated by either surgery or
conservative method for at least 1 year prior inclusion.
The data were collected at the outpatient clinic during the
study period between September 2008 and October 2009.
Other criteria included age more than 12 years and an
understanding of the Thai language. For the first survey,
each patient completed the SRS-22 questionnaire (Thai
version) and the previously validated Thai version of the
Short Form-36 version 2 (SF-36v2) health survey ques-
tionnaires [12–14]. By comparing the scoring in the cor-
relating domains of the SRS-22 and SF-36v2, we could
then determine the validity of the Thai version of the
SRS-22 questionnaire [15].
A second survey was then performed about 10 days
later. We sent the SRS-22 questionnaire (Thai version) to
the same patients and then returned the completed form by
mail. This test–retest design was used to measure the
temporal stability of the questionnaire. The reproducibility
of the Thai SRS-22 was then evaluated by comparing the
domain scores of the two surveys.
Statistical analysis
Reliability assessment of the Thai version of the SRS-22
questionnaire was determined by calculating Cronbach’s
alpha statistic and intraclass correlation coefficient (ICC)
values. According to Asher et al. [6], the Cronbach a of
internal consistency was defined as follows: very satisfac-
tory (Cronbach a 0.80–0.89), good (Cronbach a 0.50–0.79),
lower than the original questionnaire\0.5. For test–retest
reproducibility, the ICC was defined as follows: excellent
(ICC C 0.75), good (ICC 0.40–0.75) [16]. Concurrent
validity was evaluated by comparing SRS-22 domains with
relevant domains in the SF-36 questionnaire. Correlation
was made using the Pearson correlation coefficient (r),
interpreted as: excellent[0.75, good 0.50–0.75, moderate
0.25–0.50, poor \0.25 [8, 10]. Statistical difference was
defined as a P-value of less than 0.01. All analyses in this
study were calculated by STATA 10.0 (STATACORP,
College Station, Texas).
Results
In total, 34 patients met the inclusion criteria during the
study period. Four patients did not complete or return a
second questionnaire, thus, 30 patients were enrolled in the
study. There were two males and 28 females, with a mean
age of 17.2 years (range, 13–30 years). The mean gap
between the first and the second mailings was 10 days
(range, 7–14 days).
The distribution of scores for five SRS-22 and nine
SF-36v2 domains in terms of domain means, minimum
floor score, and the ceiling and floor effect for both of the
translated Thai versions of SRS-22 and SF-36v2 are shown
in Table 1. All of the SRS-22 domains demonstrated a low
level of floor effect (less than 7%, as shown in Table 1),
but a domain (vitality) of SF-36v2 exhibited a high level of
floor effect (more than 7%). Three domains of SRS-22
(pain, functional/activity, and satisfaction with manage-
ment) and six domains of SF-36v2 (physical function, role
limitations due to physical health problems, role limitations
due to emotional problems, social functioning, bodily pain,
and health transition) resulted in a high level of ceiling
effect.
Table 2 shows the comparison between SRS-22 and
SF-36v2 domains by converting the score of the SRS-22
from a 0–5 to a 0–100 scale, followed by analysis distri-
bution into quartiles. Score distributions were weak and
tended to be high in all domains of SRS-22 and in the SF-
36v2 domains of physical function, role limitations due to
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physical health problems, role limitations due to emotional
problems, social functioning, bodily pain, and health
transition.
Table 3 shows the internal consistency assessment of
SRS-22 by using the Cronbach’s alpha value. The results
were very satisfactory (Cronbach a = 0.80–0.89) in the
self-image/appearance, functional/activity,
health domains, and showed good consistency (Cronbach
a = 0.50–0.79) in the pain and satisfaction with manage-
ment domains. Also, the Cronbach’s alpha value of SF-
and mental
36v2 had a similar value from a previous publication, thus,
we could calculate the concurrent validity properly [13].
Table 4 shows the test–retest reproducibility by using
statistical analysis of the ICC. There were excellent (ICC[
0.75) results in all of the domains except for pain and
satisfaction of management, which showed good (ICC =
0.40–0.75) results.
Table 5 shows the concurrent validity in comparison
with SF-36v2. The correlation was calculated by the
Pearson correlation coefficient (r). We found statistical
Table 1 Descriptive statistics
on individual domain scores
* SRS-22 scale: 5 = best;
1 = worst
** SF-36v2 scale: 100 = best;
0 = worst
Questionnaire/domain
(no. of questions)
Domain
mean (SD)
Floor
score
minimum
% with
floor
effect
% with
ceiling
effect
SRS-22*
Pain (5) 4.44 (0.53) 3.203.30 23.30
Self-image/appearance (5)3.72 (0.79)2.203.30 6.70
Functional/activity (5)4.46 (0.58)3.206.70 33.30
Mental health (5) 3.95 (0.67) 2.403.303.30
Satisfaction with management (2)4.42 (0.62)3.006.70 40.00
SF-36v2**
Physical function (10)84.83 (13.23)55.003.30 30.00
Role limitations due to physical health problems (4)86.67 (16.39)38.003.3043.30
Role limitations due to emotional problems (3)85.83 (20.89)17.003.30 53.30
Vitality (4) 69.58 (18.40)38.00 10.006.70
Mental health (5)73.00 (16.74)40.006.70 3.30
Social functioning (2) 90.00 (13.69) 50.003.3053.30
Bodily pain (2)84.75 (17.57) 50.003.30 43.30
General health (5)70.83 (17.81)35.00 3.303.30
Health transition (1)64.17 (22.44)25.00 6.70 20.00
Table 2 Distribution of SRS-22 and SF-36v2 domain scores by quartiles
Quartiles (%) Pain Self-image/
appearance
Functional/
activity
Mental
health
Satisfaction with
management
SRS-22 domains
100100.00 100.00100.00100.00 100.00
75 100.00 75.00100.0075.00100.00
50100.0075.00 100.0075.0075.00
2575.0050.00 75.0075.0075.00
0 64.0044.0064.0048.0060.00
Quartiles (%)Physical
functioning
Role limitations
due to physical
health problems
Role limitations
due to emotional
problems
Vitality Mental
health
Social
functioning
Bodily
pain
General
health
Health
transition
SF-36v2 domains
100100.00 100.00100.00 100.00100.00100.00 100.00100.00100.00
75 100.00100.00 100.0082.8180.00 100.00 100.0085.0075.00
5085.0093.75100.0068.7575.00 100.0090.0075.0050.00
2575.0073.0075.0056.2563.75 87.5067.5055.00 50.00
0 55.0038.0017.0038.0040.0050.0050.0035.0025.00
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significance in all of the domains except that in satisfaction
with management of the SRS-22, which did not correlate
with all of the related domains of SF-36v2 (physical
function, role limitations due to physical health problems,
bodily pain, general health, and health translation). So,
there was excellent correlation (r C 0.75) in two domains,
good (r = 0.50–0.75) in six domains, moderate (r =
0.25–0.50) in five domains, and poor (r\0.25) in five of
the 18 relevant domains.
Discussion
In this study, we culturally and linguistically adapted the
SRS outcome instrument (SRS-22) into Thai. The first part
of the study showed that most of the patients recruited into
the study expressed mild clinical complaints, as the lowest
score in all of the domains was only 2.2 and the percentage
of floor effect in each domain was also less than 7%. The
score distribution, in Table 2 (converting the score of SRS-
22 from 0–5 to 0–100), shows that, in each of the domains,
most of the patients had a score of more than 50 and many
over 75. This score distribution correlates well with the
SF-36v2 scores and represents that the patients could
answer both questionnaires in the same way.
The mean value of the Cronbach’s alpha obtained from
the Thai version of SRS-22 was slightly lower than the
original study (0.78 vs. 0.86) [6]. Although this tendency
has been observed in other transcultural adaptations of
questionnaires [9], the lower internal consistency of satis-
faction with management domain was principally respon-
sible for the lower Cronbach’s alpha value. This might be
explained by the fact that Thai people usually have respect
for doctors. For example, though they are unsatisfied with
the result of their back treatment, they are likely to respond
that they are happy with the treatment. Conversely, in the
second question of this domain, ‘‘Do you want to have the
same management if you have the same condition?’’, they
select the choice ‘‘no’’ instead of stating that they are
unsatisfied with their treatment. Therefore, low Cronbach’s
alpha value was identified in this domain. In addition, as
there are only two questions in this domain, the internal
consistency showed a slightly lower value of Cronbach’s
alpha.
The test–retest reproducibility demonstrated excellent or
at least a good reproducibility with high ICC levels in all
domains which are comparable to the original question-
naire [5]. This means that there was acceptable reproduc-
ibility of this Thai version of the SRS-22 questionnaire.
Moreover, the study of concurrent validity resulted in an
excellent correlation coefficient when compared with
SF-36v2, except in the satisfaction of management domain.
As stated above, the possible reasons for this point include
the fact that the response to these questions in the SRS-22
relate to the patient’s feelings toward their physician’s
treatment. Since Thai patients are considerate of their
doctors’ feelings, it is possible that they usually respond in
a positive way. On the other hand, the correlated domain
from the SF-36v2 usually refers to the patient’s feeling
towards their back condition or their limitation of activity,
and Thai patients are more likely to respond accordingly.
Secondly, Lai et al. demonstrated that the SRS-22 man-
agement satisfaction domain correlated poorly with the
related domains of SF-36, while the other domains showed
a satisfactory correlation [16]. Consequently, we propose
that the lower correlation coefficient in our study was a
reflection of both the intrinsically poor correlation of the
satisfaction with management domain of the SRS-22 with
Table 3 Internal consistency reliability (Cronbach’s alpha value)
SRS-22 domain
a
SF-36v2 domain*A
Pain 0.72Physical function0.76
Self-image/appearance0.87Role limitations due to physical health problems 0.87
Functional/activity0.83 Role limitations due to emotional problems0.89
Mental health0.83 Vitality 0.77
Satisfaction with management 0.63 Mental health0.82
Social functioning 0.72
Bodily pain0.82
General health0.77
* All of the domains were calculated except for health transition because it has only one choice for this domain
Table 4 Test–retest reproducibility as determined by the intraclass
correlation coefficient (ICC)
SRS-22 domainICC
Pain 0.72
Self-image/appearance0.85
Functional/activity0.81
Mental health 0.82
Satisfaction with management 0.62
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the related domains of SF-36 and the Thai culture, rather
than a validity problem of the translated questionnaire. The
satisfaction with management domain in our translated
SRS-22 should be carefully interpreted when this ques-
tionnaire is used in scoliosis patients.
There are a number of limitations of our study. The
number of subjects could have been greater. In addition,
the study was conducted at one institution; a multicenter
study would provide a wider range of severity of scoliosis
patients, which may improve the quality of analysis.
However, we could demonstrate a reliable, valid, and
reproducible translated questionnaire using a sample size
recommended by the guideline for cross-cultural adapta-
tion process, which could be used further in clinical sco-
liosis research in our societies.
Conclusion
In order to effectively use a health-related quality of life
questionnaire across cultures, we always consider both
cultural adaptation and linguistic translation as important
issues. The Thai version of the Scoliosis Research Society-
22 (SRS-22) outcome instrument has satisfactory internal
consistency,goodto excellent
acceptable validity. Thus, it may be used as a standard
assessment in clinical studies of idiopathic scoliosis in Thai
language societies.
reproducibility,and
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Table 5 Concurrent validity of SRS-22 domains with relevant SF-36v2 domains as determined by the Pearson correlation coefficient (r)
SRS-22 domain SF-36v2 domainPearson rP-value*
Pain Physical function0.450.01
\0.01
\0.01
0.01
\0.01
\0.01
\0.01
\0.01
\0.01
0.01
\0.01
\0.01
\0.01
0.60
Role limitations due to physical health problems0.59
Bodily pain0.77
Self-image/appearancePhysical function0.43
Social functioning0.63
General health0.49
Functional/activityPhysical function 0.62
Role limitations due to physical health problems 0.58
Bodily pain0.52
General health0.45
Mental healthVitality0.70
Mental health0.75
Social functioning0.47
Satisfaction with management Physical function 0.10
Role limitations due to physical health problems 0.020.92
Bodily pain-0.020.91
General health 0.080.68
Health transition-0.03 0.88
* Correlation is significant at the 0.01 level (two-tailed)
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