study on the reliability and validity of the korean ... · the k-swal-qol is able to assess several...

Study on the Reliability and Validity of the Korean Swallowing-Quality of Life Questionnaire (K-SWAL-QOL)

Tae-Hyun Cha

The Graduate SchoolYonsei University

Department of Occupational Therapy

Study on the Reliability and Validity of the Korean Swallowing-Quality of Life Questionnaire (K-SWAL-QOL)

A DissertationSubmitted to the Department of Occupational Therapy

and the Graduate School of Yonsei Universityin partial fulfillment of the

requirements for the degree of Doctor of Philosophy

Tae-Hyun Cha

December 2013

This certifies that the dissertation ofTae-Hyun Cha is approved.

____________________________________________________________ Thesis Supervisor: Min-Ye Jung

_____________________________________________________________

Eun-Young Yoo

_____________________________________________________________ Ji-Hyuk Park

_____________________________________________________________

Kyeong-Mi Kim

______________________________________________________________

Ki-Yeon Chang

The Graduate School Yonsei University June 2013

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Acknowledgements

I would like to thank Professor Min-ye Jung from the bottom of my heart,

who has ceaselessly provided guidance and attentive care ever since my

undergraduate days throughout my master's and to the day I completed by

doctoral thesis. For more than 15 years, you have given me the guidance of

trust and faith; I will do my absolute best in the coming years to return your

lifetime of teaching.

My sincere thanks to the following individuals, to whom I’ll ever be

grateful: Professor Eun-young Yoo, for teaching me the right academic

attitude; Professor Ji-hyuk Park, who has taught me the character of a

researcher; Professor Ki-yeon Chang, for leading me to a life that’s real;

Professor Kyeong-mi Kim, for her generous words of encouragement; and

Professor Soo-hyun, who has demonstrated true learning through passion. I

would like to convey my words of appreciation to all the hospital occupational

therapists who have assisted me with the recruitment of study subjects and all

the way through the data collection, and foremost, all those study subjects

who have trusted me and participated in the study.

My sincere thanks to the following officers of the Korean Academy of

Dysphagia Rehabilitation, to whom I’m grateful for the generous support they

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have bestowed upon me all the way up until the completion of my paper:

Director Ji-hyeon Choi, Professor Ji-young Baek, Professor Hui-sun Woo,

Professor Seong-yun Won, Mr. Won-il Song, Mr. Gyeong-cheol Min, Mr.

Sang-min Seo, Ms. Soo-jung Lee, Ms. Bo-un Choi, Mr. Hyo-jun Yang, Mr.

Sang-gyun Park, Mr. Du-kyu Kim, and others. My thanks to the following

professionals who have tirelessly provided their support from early morning

until late at night at the occupational therapy department of the graduate

school – while devoting themselves to their academic fields – so as to ensure that my graduate thesis study can proceed without a hitch: Mr. Joo-hyeon Lee,

Mr. Hae-yun Jung, Mr. Young-jo Kim, and also other fulltime instructors at

the graduate school, and Mr. No-yeol Yang who was generous with helpful

advice. I also want to thank Professor Jae-shin Lee for being the constant

source of strength for me and Professor Su-gyeong Kim for providing me with

her precious words of wisdom, and Professor Jin-ah Sohn for always being

there for me. I want to thank Professors Young-seok Park and Young-bin Yoo

for their encouragements from the start.

I would like to send my words of appreciation to Professors Eun-ju Kim

and Jong-chi Oh for being with me during the three year period from the

outset of this paper; and I am thankful to my father, sister and brothers who

have supported me until the completion of my paper, and especially to my

mother in heaven, I would like to dedicate this thesis. I am thankful to my

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precious two daughters, Ji-hu cha and Ji-min Cha, for growing up healthy and

vibrant, and more than anything, I am thankful to – and I want to express my love for – the most beautiful and valuable lady in this world, Sook-yeon Shin, for her thoughtful and truthful advice over the last 20 or so years as my life

partner.

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Table of Contents

List of Figures ·········································································································· vii

List of Tables ·········································································································· viii

Abstract ························································································································ x

Introduction ·················································································································· 1

Methods ························································································································ 6

1. Study subjects and procedure ··········································································· 6

1.1. Adaptation process of the SWAL-QOL ··················································· 9

1.1.1. Translation and back-translation of the SWAL-QOL ···················· 10

1.1.2. Assessment of the appropriateness of questions in the K-SWAL-

QOL and completion of the final Korean version ······················· 11

1.2. Subject and method of reliability testing ·············································· 12

1.2.1. Internal consistency ············································································ 12

1.2.2. Test-retest reliability ·········································································· 15

1.3. Subject and method of validity testing ·················································· 18

1.3.1. Convergent validity ············································································ 18

1.3.2. Discriminant validity ·········································································· 18

1.4. Clinical utility ··························································································· 26

2. Study Tools ······································································································ 28

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2.1. Swallowing quality of life(SWAL-QOL) ··············································· 28

2.2. Korean version of the world health organization quality of life scale

abbreviated(K-WHOQOL-BREF) ···························································· 29

2.3. Korean Hamilton rating scale of depression(K-HDRS) ······················· 31

3. Data Analysis ··································································································· 32

Results ························································································································ 33

1. Development of the Korean SWAL-QOL ···················································· 33

1.1. Assessing the appropriateness of the modified Korean SWAL-QOL

questions ····································································································· 33

2. Testing the Reliability of The Korean SWAL-QOL ··································· 36

2.1. Internal consistency ··················································································· 36

2.2. Test-retest reliability ················································································· 40

3. Validity Testing ································································································ 41

3.1. Convergent validity ··················································································· 41

3.1.1. Convergent validity using the K-SWAL-QOL and K-WHOQOL-

BREF ···································································································· 41

3.1.2. Convergent validity using the K-SWAL-QOL and K-HDRS ······ 43

3.2. Discriminant validity ················································································· 45

3.2.1. Discriminant validity through comparison between normal subjects

and patients with swallowing disorders ········································· 45

3.2.2. Discriminant validity depending on oral intake ····························· 47

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3.2.3. Discriminant validity the K-SWAL-QOL depending on diet ······· 49

4. Clinical Utility ·································································································· 51

Discussion ·················································································································· 52

Conclusion ················································································································· 59

References ·················································································································· 61

Appendix ···················································································································· 76

Abstract in Korean ··································································································· 86

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List of Figures

Figure 1. Process of translation, reliability and validity of SWAL-QOL ··········· 8

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List of Tables

Table 1. Demographic characteristics of participants in the survey on internal

consistency ······························································································· 14

Table 2. Demographic characteristics of participants in the survey on test-retest

reliability ···································································································· 17

Table 3. Demographic characteristics of normal subject ··································· 21

Table 4. Demographic characteristics of participants for discriminant validity

depending on oral intake ········································································· 23

Table 5. Demographic characteristics of participants for discriminant validity

the K-SWAL-QOL depending on diet ··················································· 25

Table 6. Survey item on clinical utility ······························································ 27

Table 7. Sub-scale and Cronbah’s α of K-WHOQOL-BREF ··························· 30

Table 8. Mean and CVI according to an modified K-SWAL-QOL ················· 34

Table 9. The internal consistency of items in the K-SWAL-QOL ··················· 37

Table 10. The areal internal consistency in the K-SWAL-QOL ························ 39

Table 11. The areal test-retest reliability in the K-SWAL-QOL ······················· 40

Table 12. The correlation between K-SWAL-QOL and K-WHOQOL-BREF ·· 42

Table 13. The correlation between K-SWAL-QOL and K-HDRS ····················· 44

Table 14. Comparison of the K-SWAL-QOL’s areal mean score between

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swallow disorders and normal subjects ··············································· 46

Table 15. Comparison of the K-SWAL-QOL’s areal mean score depending on

oral intake ······························································································· 48

Table 16. Comparison of the K-SWAL-QOL’s areal mean score depending on

diet ··········································································································· 50

Table 17. Clinical utility results of K-SWAL-QOL ············································ 51

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ABSTRACT

Study on the Reliability and Validity of the Korean Swallowing-Quality of Life Questionnaire

(K-SWAL-QOL)

Tae-Hyun Cha

Dept. of Occupational Therapy

The Graduate School

Yonsei University

The purpose of the present study was to examine the usefulness of creating

a Korean version of the SWAL-QOL, which measures quality of life related to

swallowing, by assessing its reliability and validity.

The translation process for this measure involved correcting inappropriate

vocabulary through translation, modifying sentences with errors in meaning

through back-translation, and completing the final Korean version by assessing

the appropriateness of the questions.

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Reliability was assessed via internal consistency and test-retest reliability

analyses, while convergent validity and discriminant validity were also

examined. In addition, experts tested the clinical utility of this measure. In

order to obtain convergent validity, correlations between the K-WHOQOL-BREF

and K-HDRS, which assess quality of life related to health and levels of

depression, respectively, were compared. In order to test the discriminant

validity, all categories of the K-SWAL-QOL were compared between patients

with a swallowing disorder and normal subjects, while all categories of the

K-SWAL-QOL were compared and analyzed depending on the diet and feeding

type. The Cronbach’s α and Pearson's correlation coefficients (r) for test-retest

reliability ranged between 0.54-0.91 and 0.80-0.98, respectively. For convergent

validity, a significant correlation (p < .001) was observed for all categories on

comparing the K-WHOQOL-BREF and K-HDRS. Results of discriminant

validity showed a significant difference between patients with swallowing

disorders and normal subjects for all categories of the K-SWAL-QOL (p <

.001) as well as differences based on diet and feeding type (p < .001). A test

of clinical utility revealed significant results regarding the use of this measure

for clinical assessment and treatment of swallowing disorders.

The K-SWAL-QOL is able to assess several aspects of quality of life

related to swallowing. The K-SWAL-QOL appears to be a reliable and valid

assessment tool. In the future, this measure should be used as a means of

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providing appropriate intervention for occupational therapy and rehabilitation.

Key words: Clinical utility, Quality of life, Reliability, Swallowing disorder,

Validity

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Introduction

For humans, eating and drinking satisfy our most fundamental desires while

also bringing pleasure, happiness, and satisfaction. Eating and drinking play a

very important psychosocial role (Chen et al., 2001). Patients with swallowing

disorders lose the pleasure of eating through the mouth and show a reduced

quality of life due to depression or social isolation (Aledort et al., 2012). This

is because these individuals are unable to experience the joy of eating

(Smithard, 2000). Swallowing disorders are, generally, secondary functional

disorders (Kurre, Scholl, Bullinger, & Petersen-Ewert, 2011) seen in patients

with other diseases (cancer, gastroesophageal diseases, neurological disorders).

However, swallowing disorders have recently been observed in healthy

elderly populations displaying reduced physical functioning, manifesting in

symptoms such as reduced masticatory function, delayed swallowing reflexes,

reduced hyolaryngeal excursion, and decreased airway protection (Hoffmeister

et al., 2011). In addition to physical problems, patients with swallowing

disorders tend to be more prone to psychosocial symptoms such as being

angry at others or complaining more about depression compared to other

patient groups (Bullinger, 2011); the failure to engage in successful social

interaction during meal times negatively affects quality of life (Rucker et al.,

2011).

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Currently, assessment tools for measuring swallowing disorders mostly focus

on physical aspects of these disorders (as revealed through endoscopy and

videofluoroscopy studies; Logemann, Rademaker, Pauloski, Ohmae, & Kahrilas,

1998). Such tools only assess the physical and functional aspects of

swallowing but do not address a patient’s quality of life (Khaldoun, Woisard,

& Verin, 2009). Only recently has the importance of measuring how such

diseases influence quality of life been recognized (Costa Bandeira et al., 2008).

In order to assess quality of life in patients with swallowing disorders,

McHorney et al. (2002) supplemented the limitations of existing assessment

tools by creating the SWAL-QOL, which consists of 44 questions that assess

11 quality of life concepts based on components such as the following: (1) the

ability to achieve daily or desired physical and social activities, (2) the

psychosocial effects of performing daily and desired activities, (3) the level of

satisfaction with medical services related to swallowing treatment, and (4)

disease level before assessing the validity of the scale (McHorney et al.,

2002).

Since its development, the SWAL-QOL has been used to study quality of

life in patients with swallowing disorders due to brain damage (Lovell, Wong,

& Loh, 2005), while also assessing quality of life as a result of progressive

diseases such as head and neck cancer, Parkinson’s disease, multiple sclerosis,

Alzheimer’s disease, and amyotrophic lateral sclerosis (Rinkel et al., 2009).

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This tool has the advantage of being able to quantitatively evaluate the effects

of swallowing disorders on both individuals’ social lives and dietary constraints

(Heidel et al., 2012).

Recent leading studies in this area have assessed the relationship between

swallowing issues and quality of life in Parkinson's Disease patients

(Plowman-Prine et al., 2009), head and neck cancer patients (Campbell et al.,

2004; Claus, Plass, Armstrong, & Bullinger, 2010), dysphasia in the elderly

(Chen et al., 2001; Eslick & Talley, 2008)) and oropharyngeal cancer patients

(Blazeby, Williams, Brookes, Alderson, & Farndon, 1995; Costa Bandeira et

al., 2008; Infante-Cossio, Torres-Carranza, Cayuela, Gutierrez-Perez, &

Gili-Miner, 2009; Theilgaard-Monch et al., 2011). Thus, the SWAL-QOL was

developed to assess psychosocial aspects of swallowing disorders (McHorney et

al., 2002) and is a standardized tool for measuring quality of life resulting

from swallowing disorders that are caused by various factors (Leow, Huckabee,

Anderson, & Beckert, 2010; McKinstry, Tranter, & Sweeney, 2010; Rinkel et

al., 2009). While the usefulness of this tool is being confirmed, it is being

actively used in several countries (the Netherlands, France, Sweden, China;

Bogaardt, Speyer, Baijens, & Fokkens, 2009; Khaldoun et al., 2009; Li et al.,

2012; Noordermeer et al., 2011).

There are limitations with adapting the SWAL-QOL to other languages due

to inappropriate content or an inability to use standardized scores owing to

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cultural and linguistic differences (Fiedler et al., 2011). Therefore, when

adapting a questionnaire developed for a particular culture for use in a

different culture with a different language, systematic translation and validity

tests are essential (Beaton, Bombardier, Guillemin, & Ferraz, 2000).

Furthermore, in order to apply this questionnaire to a clinical setting, an

additional testing process for assessing clinical utility is necessary to determine

whether this measure provides something extra beyond existing assessment

tools (Leonardi et al., 2010). However, evaluating a psychological assessment

questionnaire is an endless procedure, is always inferential, and the field is

never fully established ((Wainer, 1988). For this reason, a study that considers

swallowing disorder severity and various patient samples might be addressed

when studying the SWAL-QOL’s reliability and validity (Vanderwegen et al.,

2012).

For assessment tools used with swallowing disorder patients, there have been

studies comparing the status before and after a dietary intervention with a

translated version of the SWAL-QOL. However, these studies examined the

correlation between swallowing enhancement and quality of life in 21 central

nervous system patients prior to testing the validity and reliability of the

measure post-translation (Cha, 2008). Recently, a study by Kim (2012) was

conducted to assess the reliability and validity of the SF-36 with 53 normal

subjects and 53 patients with cancer, vascular disease, degenerative diseases,

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and swallowing disorders .

Therefore, the purpose of the present study was to test the reliability,

clinical validity, and clinical utility of the Korean version of the SWAL-QOL

(K-SWAL-QOL) through a translation process in order to utilize this scale in

Korea.

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Methods

1. Study Subjects and Procedure

Subjects included a total of 126 hospitalized patients with brain damage or

outpatients from medical institutions across Korea assessed between October 1,

2012 and October 6, 2013. The purpose and method of the study were

explained to occupational therapists at each medical institution, and patients

that met the inclusion criteria were selected as subjects. Inclusion criteria

included the following: (1) patients with oropharyngeal dysphagia confirmed by

a video fluoroscopic swallowing study (VFSS) or endoscopy; (2) patients that

were neurologically stable; (3) patients that could express or understand

verbally/nonverbally with an MMSE-K score of at least 24 points; (4) patients

did not have swallowing disorders caused by a pure esophageal disorder; and

(5) patients agreed to participate in the study. Normal subjects included

members of the community who have never been diagnosed with a swallowing

disorder and currently do not have a swallowing disorder.

The current study was conducted in 4 phases. During the first phase, the

Korean version of the SWAL-QOL was developed through translation; during

the second and the third phases, the reliability and validity of the measure

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were tested. In the final phase, the clinical utility of this assessment was

confirmed (Fig. 1).

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Phase 1SWAL-QOL Translation

process

Translation(2 experts)

Back-translation(1 expert)

Final Korean SWAL-QOL : Committe(1 Professor, 3 Occupational therapists)

Phase 2Content Validity

Assessment of the appropriateness of questions : Survey(1 Rehabilitation specialist, 7 Occupational therapists)

Phase 3Reliability

Internal consistency(126 Swallowing disorders) Test-retest reliability(20 Swallowing disorders)

Phase 4Validity

Convergent validity: K- WHOQOL, K-HDRS(126 Swallowing disorders)

Discriminant validity(126 Swallowing disorders, 102 Normal subjects)

(Oral intake: 104 oral, 22 non-oral intake) (Diet: 40 pudding, finely 32 chopped food,

32 soft-boilded rice)

Phase 5Clinical utility

Clinical utility : Survey(30 Occupational therapists)

Figure 1. Process of translation, reliability and validity of SWAL-QOL

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1.1. Adaptation process of the SWAL-QOL

Prior to conducting this study, approval was obtained from the author of the

original measure in order to adapt the SWAL-QOL into Korean. The

adaptation process was conducted in four steps (translation, back-translation,

assessment of the appropriateness of the questions, and completion of the final

Korean version of SWAL-QOL). The adaption process was conducted by

modifying and supplementing the translation and back-translation process based

on criteria provided by Beaton et al. (2000).

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1.1.1 Translation and back-translation of the SWAL-QOL

Two expert translators participating in the translation of the SWAL-QOL

were non-majors of occupational therapy with no prior experience with the

SWAL-QOL. The experts were native Korean speakers but also spoke English.

During the research step of this study, the translators individually translated the

SWAL-QOL from English to Korean and corrected inappropriate vocabulary

through a panel meeting attended by researchers and the translators.

One native English speaking expert (who also spoke Korean) translator who

did not major in occupational therapy back translated the SWAL-QOL. The

back-translator re-translated the Korean version into English. Subsequently, a

panel meeting was held for the validation of the back-translation with the

researchers and a bilingual professor who spoke both Korean and English and

holds a doctoral degree in clinical psychology from the United States. Based

on the results of the translation process, three items were modified.

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1.1.2 Assessment of the appropriateness of questions in the K-SWAL-QOL

and completion of the final Korean version

In order to check for consistency in the semantics, idioms, experience, and

concepts of the Korean version, committee was held with three clinical

occupational therapists and one linguistics professor. As a result, the final

version of the Korean SWAL-QOL was completed after modifying the

vocabulary and syntax of nine out of the 44 questions.

This step of the study was conducted in order to remove inappropriate

questions by testing the appropriateness of 11 K-SWAL-QOL items modified

through the translation and back-translation process. A survey was conducted

with eight rehabilitation experts (1 rehabilitation specialist and 7 occupational

therapists with at least 3 years of experience), where the appropriateness of

each question was rated on a 5-point Likert scale (5 points: very appropriate,

4 points: appropriate, 3 points: average, 2 points: inappropriate, 1 point: very

inappropriate). Subsequently, the Content Validity Index (CVI) was calculated

in order to check for the presence of inappropriate questions, and results

showed that there were no questions with a CVI value less than 0.50; a value

less than 0.50 would indicate inappropriateness of the question (Polit, Beck, &

Owen, 2007; Shelley, 1984).

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1.2. Subject and method of reliability testing

A test of internal consistency and test-retest reliability was conducted in

order to assess the reliability of the Korean SWAL-QOL.

1.2.1 Internal consistency

Testing internal consistency is a way of verifying the reliability of a

measure by analyzing whether questions included to measure the same concept

have similar reliability coefficients. The reliability coefficient most commonly

used for calculating internal consistency is Cronbach’s α (Jeong & Sohn,

2010). The criteria for Cronbach’s α vary depending on the discipline, but a

value of at least 0.80 is interpreted as high internal consistency in general; a

value between 0.60-0.79 is interpreted as moderate; a value below 0.60 is

considered low.

Internal consistency was conducted over a period of 6 months from March

2013 to September 2013 among 126 patients with swallowing disorders. The

subjects were asked to answer each of the 44 questions on the measure.

Subjects were asked to fill out the questionnaire on their own, but in cases

where it was difficult, the assessor read the questions aloud and recorded the

responses.

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Subjects’ demographic information is as follows. There were 56 males

(44.4%) and 70 females (55.6%) with a mean age of 54.21 ± 9.99 years. In

terms of education, 49 subjects had no formal education (38.9%), 18 subjects

graduated elementary school (14.3%), 21 subjects graduated middle school

(16.7), 13 subjects graduated high school (10.3%), and 25 subjects graduated

from university (19.9%). For marital status, 87 subjects were married (69.0%).

In terms of diagnosis, 101 subjects were diagnosed with stroke (80.2%), and

25 subjects (19.8) were diagnosed with traumatic brain injuries. As for the

disorder onset period, 6 months to less than 1 year accounted for the highest

percentage with 62 subjects (49.2%), while current form of diet included

non-oral intake for 22 subjects (17.5.%), puddings for 40 subjects (31.7%),

finely chopped food for 32 subjects (25.4%), and soft-boiled rice for 32

subjects (25.4%). Most subjects came from rehabilitation hospitals: 88 subjects

(69.8%). (Table 1).

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Table 1. Demographic characteristics of participants in the survey on internal consistency (N=126)

Characteristics Number (N) Percent (%)

GenderMale 56 44.4

Female 70 55.6

Age

30~39 years 14 11.140~49 years 35 27.850~59 years 35 27.860~69 years 36 28.670~79 years 6 4.8

Education

Illiteracy 49 38.9Elementary school graduation 18 14.3

Middle school graduation 21 16.7High school graduation 13 10.3

College graduation or more 25 19.9

Marital status

Single 8 6.3Married 87 69.0

Divorce or separation 14 11.1Bereavement 17 13.5

DiagnosisCVA 101 80.2TBI 25 19.8

Onset period

0~3 months 6 4.83~6 months 23 18.3

6 months~1 year 62 49.21 year or more 35 27.8

oral intake

Nonoral 22 17.5Pudding 40 31.7

Finely chopped food 32 25.4Soft-boiled rice 32 25.4

PlaceGeneral hospital 8 6.3

Rehabilitation hospital 88 69.8Hospital care 30 23.8

TreatmentHospitalization 94 74.6

Outpatient 32 25.4

- 15 -

1.2.2 Test-retest reliability

Test-retest reliability is a method of estimating reliability based on

correlation coefficients obtained from conducting the same test twice with a

certain time interval by the same administrator (Seong, 2012).

Test-retest reliability was conducted with 20 subjects within the same period as

the internal consistency testing. The questionnaire was administered to subjects

with a 2-week interval between testing.

Prior to the test-retest reliability analysis, a comparison of general

demographic information was conducted between the group given the retest (n

= 20) and the group not given the retest (n = 106). There were no

statistically significant differences between the groups for diet, gender, age,

education, marital status, diagnosis, onset period, and form of treatment.

- 16 -

Subjects who participated in the test-retest phase included 8 males (40.0%)

and 12 females (60.0%) with a mean age of 54.8 ± 10.7 years. Regarding

education, 8 subjects had no formal education (40.0%), 2 subjects graduated

elementary school (10.0%), 6 subjects graduated middle school (30.0), 1

subject graduated high school (5.0%), and 4 subjects graduated from university

(20.0%). For marital status, 16 subjects were married (80.0%). In terms of

diagnosis, 15 subjects were diagnosed with stroke (75.0%), and 5 subjects

(25.0%) were diagnosed with traumatic brain damage. For period of onset, 6

months to less than 1 year accounted for the highest percentage (13 subjects;

65.0%), while current diet included non-oral intake for 5 subjects (25.0%),

puddings for 7 subjects (35.0%), finely chopped food for 2 subjects (10.0%),

and soft-boiled rice for 6 subjects (30.0%). In terms of institution, 17 subjects

(85.0%) were in a rehabilitation hospital (Table 2).

- 17 -

Table 2. Demographic characteristics of participants in the survey on test-retest reliability (N=20)

Characteristics Number (N) Percent (%)

GenderMale 8 40.0

Female 12 60.0

Age


Education




Marital statusSingle 16 80.0

Married 4 20.0

DiagnosisCVA 15 75.0TBI 5 25.0

Onset period3~6 months 2 10.0

6 months~1 year 13 65.01 year or more 5 25.0

oral intake

Nonoral 5 25.0Pudding 7 35.0

Finely chopped food 2 10.0Soft-boiled rice 6 30.0

PlaceGeneral hospital 3 15.0

Rehabilitation hospital 17 85.0

TreatmentHospitalization 15 75.0

Outpatient 5 25.0

- 18 -

1.3 Subject and method of validity testing

A test of convergent and discriminant validity was conducted to verify the

validity of the Korean SWAL-QOL.

1.3.1. Convergent validity

All patients who participated in the internal consistency testing (Table 1)

participated in the convergent validity testing of the Korean SWAL-QOL; this

was performed during the same period as the internal validity testing. In order

to calculate convergent validity, the Korean Hamilton Rating Scale for

Depression (K-HDRS) and the Korean World Health Organization Quality of

Life scale were used as they assess a concept similar to that measured in the

K-SWAL-QOL.

1.3.2 Discriminant validity

The most frequently used method for measuring discriminant validity is

group comparisons. High discriminant validity can be inferred when there is a

significant difference between two groups after conducting a test that is likely

to show a difference based on characteristics that are already known for the

- 19 -

concept to be measured (Lee, 2012).

Discriminant validity was assessed from July to September 2013. To test for

discriminant validity, normal subjects were compared with patients, while only

differences in oral intake habits and dietary practice were compared among the

patients. In order to examine differences between normal subjects and patients,

an assessment was conducted with 102 normal subjects and the 126 patients

that participated in the internal consistency testing. The normal subjects

included those that were residing in the community, who had never been

diagnosed with a swallowing disorder, and currently had no swallowing

disorder symptoms (based on a MMSE-K score of at least 24 points). In order

to confirm differences depending on oral intake habits, the patients were

categorized into a non-oral intake group and an oral intake group, while

dietary restrictions were classified into puddings, finely chopped food, and

soft-boiled rice in order to analyze differences according to diet.

- 20 -

Prior to analyzing discriminant validity, a test of homogeneity was conducted

that revealed there was no statistical difference between the swallowing

disorder group (n = 126) and normal subject group (n = 102) in terms of age

and education.

The normal subject group (control group) included 36 males (35.3%) and 66

females (64.7%) with a mean age of 54.21 ± 9.99 years. Regarding education,

43 subjects had no formal schooling (42.2%), 17 subjects graduated elementary

school (16.7%), 1 subject graduated middle school (1.0), 10 subjects graduated

high school (9.8%), and 31 subjects graduated from university (30.4%). As for

marital status, 70 subjects were married (68.6%; Table 3).

- 21 -

Table 3. Demographic characteristics of normal subject (N=102)

CharacteristicsNormal subject

(N=102)Number (N) Percent (%)

GenderMale 36 35.3

Female 66 64.7

Age


Education




Marital status

Single 2 2.0Married 70 68.6

Divorce or separation 9 8.8Bereavement 21 20.6

- 22 -

No statistically significant difference was found between the non-oral intake

group (n = 22) and the oral intake group (n = 104) in terms of gender,

marital status, diagnosis, onset period, type of institution, and form of

treatment.

There were more females in the non-oral intake group than males (mean

age = 63.27 ± 6.73 years), with stroke accounting for 72.7% of the diagnoses.

In addition, onset period was between 6 months and less than 1 year for 10

subjects (45.5%), and 90.9% of the sample were hospitalized. There were also

more females than males in the oral intake group, and the mean age was

52.39 ± 9.51 years. A total of 52 subjects (50.0%) had an onset period of 6

months to less than 1 year, while the number of hospitalized patients

outnumbered outpatients (Table 4).

- 23 -

Table 4. Demographic characteristics of participants for discriminant validity depending on oral intake (N=126)

Characteristics

Non-oral intake(N=22)

Oral intake(N=104)

Number (N)

Percent (%)

Number (N)

Percent (%)

Gender Male 10 45.5 46 44.2Female 12 54.5 58 55.8

Age

30~39 years 0 0.0 14 13.540~49 years 2 9.1 33 31.750~59 years 4 18.2 31 29.860~69 years 10 45.5 26 25.070~79 years 6 27.3 0 0

Education

Illiteracy 16 72.7 33 31.7Elementary school

graduation0 0.0 18 17.3

Middle school graduation

2 9.1 19 18.3

High school graduation 4 18.2 9 8.7College graduation or

more0 0.0 25 24.0

Marital status

Single 2 9.1 6 5.8Married 16 72.7 71 68.3

Divorce or separation 2 9.1 12 11.5Bereavement 2 9.1 15 14.4

DiagnosisCVA 16 72.7 85 81.7TBI 6 27.3 19 18.3

Onset period

0~3 months 2 9.1 4 3.83~6 months 2 9.1 21 20.2

6 months~1 year 10 45.5 52 50.01 year or more 8 36.4 27 26.0

oral intake

Nonoral 22 100.0 0 0.0Pudding 0 0.0 40 38.5

Finely chopped food 0 0.0 32 30.8Soft-boiled rice 0 0.0 32 30.8

PlaceGeneral hospital 2 9.1 6 5.8

Rehabilitation hospital 16 72.7 72 69.2Hospital care 4 18.2 26 25.0

TreatmentHospitalization 20 90.9 74 71.2

Outpatient 2 9.1 30 28.8

- 24 -

There were more females than males in the puddings group (mean age =

51.15 ± 9.93 years), and 77.5% of subjects were diagnosed with a stroke. In

addition, 18 subjects (45.0%) had an onset period of 6 months to less than 1

year, while 75% of the subjects were hospitalized. For the soft-boiled rice

group, there were an identical number of male and female subjects (16

subjects) with a mean age of 54.46 ± 8.62 years. A total of 18 subjects

(56.3%) had an onset period of 6 months to less than 1 year, while the

number of outpatients and hospitalized patients was identical (16 subjects). For

the finely chopped food group, there were more female subjects than males

(mean age = 51.87 ± 9.79 years) and 87.5% of subjects were diagnosed with

a stroke. As with the other two diet groups, most subjects had an onset period

of 6 months to less than 1 year, while the number of hospitalized patients

outnumbered outpatients (Table 5).

- 25 -

Table 5. Demographic characteristics of participants for discriminant validity the K-SWAL-QOL depending on diet (N=104)

Characteristics

pudding(N=40)

Finely chopped food

(N=32)

Soft-boiled rice(N=32)

Number (N)

Percent (%)

Number (N)

Percent (%)

Number (N)

Percent (%)

Gender Male 16 40.0 16 50.0 14 43.8Female 24 60.0 16 50.0 18 56.2

Age

30~39 years 8 20.0 2 6.3 4 12.540~49 years 12 30.0 9 28.1 12 37.550~59 years 12 30.0 11 34.4 8 25.060~69 years 8 20.0 10 31.3 8 25.0

Education

Illiteracy 16 40.0 9 28.1 8 25.0

Elementary school graduation

10 25.0 2 6.3 6 18.8

Middle school graduation

14 35.0 1 3.1 4 12.5

High school graduation 0 0.0 7 21.9 2 6.3

College graduation or more

0 0.0 13 40.6 12 37.4

Marital status

Single 0 0.0 2 6.3 4 12.5Married 36 90.0 21 65.6 14 43.8

Divorce or separation 0 0.0 4 12.5 8 45.0

Bereavement 4 10.0 5 15.6 6 18.7

DiagnosisCVA 31 77.5 26 81.3 28 87.5TBI 9 22.5 6 18.2 4 12.5

Onset period

0~3 months 4 10.0 0 0.0 0 0.03~6 months 10 25.0 3 9.4 8 25.0

6 months~1 year 18 45.0 18 56.3 16 50.0

1 year or more 8 20.0 11 34.4 8 25.0

PlaceGeneral hospital 4 10.0 2 6.3 0 0.0

Rehabilitation hospital 28 70.0 22 68.7 22 68.7Hospital care 8 20.0 8 25.0 10 31.3

TreatmentHospitalization 30 75.0 16 50.0 28 87.5

Outpatient 10 25.0 16 50.0 4 12.5

- 26 -

1.4 Clinical utility

A survey of clinical utility was conducted from September to October 2013

with 30 occupational therapists who had at least 3 years clinical experience

and were working at a university or rehabilitation hospital. The test was

performed on at least three patients with swallowing disorders. The

occupational therapists had a mean age of 33.25 ± 6.46 years and included 13

males (43.3%) and 17 females (56.7%) with an average clinical experience of

5.63 ± 3.20 years. A survey for confirming clinical utility was prepared by

modifying and supplementing a questionnaire on clinical utility developed by

Polgar and Barlow (2005) with references from a study by Shin (2012). The

questionnaire included seven items such as ease of assessment, level of help in

setting a treatment goal (education), ease of interpretation, and efficacy of

treatment planning. Each question was assessed on a 5-point Likert scale

ranging from “strongly disagree (1)” to “strongly agree (5)” (Table 6).

- 27 -

Table 6. Survey item on clinical utility

Survey itemStrongly disagree

Disagree

Usually AgreeStrongly

agree

Is it easy for patients to perform (understand)?” and “Is it helpful in setting treatment goals?

1 2 3 4 5

Is it useful to plan treatment goal? 1 2 3 4 5

Whether the patient is focused on? 1 2 3 4 5

Is it appropriated for evaluation time? 1 2 3 4 5Is it easy to interpret the evaluation results?

1 2 3 4 5

Is it easy to evaluate tool clinically? 1 2 3 4 5Is there significance in the overall swallowing treatment process based on the test results

1 2 3 4 5

- 28 -

2. Study Tools

2.1 Swallowing Quality of Life (SWAL-QOL)

The SWAL-QOL was developed by McHorney et al. (2002) in order to

assess the effects of a swallowing disorder on patients’ quality of life

(McHorney et al., 2002). This measure was used to provide an objective

assessment of psychosocial aspects of swallowing disorders.

The SWAL-QOL consists of 11 categories with a total of 44 questions. In

other words, the scale contains categories such as “general anxiety,” “eating

duration,” “appetite,” “swallowing disorder symptoms,” “food selection,”

“communication,” “fear,” “mental health,” “social life,” “fatigue,” and “sleep.”

Each question was rated on a scale from 1 to 5 with a total score ranging

between 44 and 220. A high score indicates good quality of life while a low

score indicates low quality of life (McHorney et al., 2002). The Cronbach’α

for this scale ranged from 0.79-0.91.

- 29 -

2.2. Korean version of the World Health Organization Quality of Life

scale abbreviated (K-WHOQOL-BREF)

The K-WHOQOL-BREF was used for convergent validity. This Korean

version is a self-report scale that subjectively assesses quality of life as

perceived by the patient over the past 2 weeks. This test incorporates one item

from 24 sub-scales of the WHOQOL. This scale has been shown to be an

appropriate assessment tool through several standardization steps in terms of

test-retest reliability, internal consistency, criterion validity, content validity, and

discriminant validity (Min, Lee, Kim, & Suh, 2000).

The specific sub-scales include a total of 26 questions, which are broken

down into 24 questions under 4 domains including 7 questions for the physical

health domain (QLS-D1), 6 questions for the psychological domain (QLS-D26),

3 questions for the social relationships domain (QLS-D3) and 8 questions for

the environmental domain (QLS-D4); an additional 2 questions assess overall

quality of life (overall QOL). The score for each question was set up so that

“Strongly disagree” corresponded to 1 point, “Somewhat disagree” corresponded

to 2 points, “Agree” corresponded to 3 points, “Strongly agree” corresponded

to 4 points, and “Very strongly agree” corresponded to 5 points. For

reverse-scored questions (numbers 3, 4 and 26), the score for each question

was subtracted from 6 points so that a high score corresponded to high quality

- 30 -

of life. The Cronbach's α for the present sample was 0.90, with the range of

coefficients ranging between 0.86-0.91 for each sub-scale (Table 7).

Table 7. Sub-scale and Cronbach’s α K-WHOQOL-BREF Sub-scale Item number Cronbach’s α

overall QOL 2 0.913

physical health domain 7 0.859

psychological domain 6 0.872

social relationships domain 3 0.876

environmental domain 8 0.876

Total 26 0.903

- 31 -

2.3 Korean Hamilton Rating Scale of Depression (K-HDRS)

The K-HDRS was used to assess convergent validity. The Korean Hamilton

Rating Scale of Depression (K-HDRS) was developed in 1960 by Hamilton

and is one of the most widely used scales in the assessment of depression

(Hamilton, 1960). Lee and colleagues (2005) developed the Korean version of

the HDRS. The HDRS consists of 17 items, which are rated on a 4-point

scale for 9 items that include depressed mood, feeling of guilt, suicide, work

and activities, retardation, agitation, psychiatric anxiety, somatic anxiety, and

hypochondriasis or on a 2-point scale for seven items including insomnia-late,

somatic-gastrointestinal, somatic general, genital symptoms, and insight. Loss of

weight is rated on a 3-point scale in some cases but is mostly rated on a

2-point scale. Reverse scoring is used for items 3, 4, and 26. The range for

total scores is 0-52, with a high score indicating severe depression. The

Cronbach's α for the present sample was 0.80.

- 32 -

3. Data Analysis

Windows SPSS 18.0 (IBM, SPSS, Inc., Chicago, IL, USA) was used for

analysis, with a significance level set at 0.05.

Results conducted to verify the appropriateness of each question were

represented by the content validity index (CVI). For the calculation of CVI, 0,

1/4, 2/4, 3/4, and 1 were assigned to each scale value of 1, 2, 3, 4, and 5,

respectively, before an arithmetic mean was calculated for each question. For

this study, the CVI cut-off score was assigned as 0.50, and activities below

the cut-off score were considered unacceptable (Polit, Beck, & Owen, 2007;

Shelley, 1984).

In addition, analysis of descriptive statistics was performed in order to

assess demographic aspects of the sample, and Cronbach’s alphas were

calculated in order to identify the internal consistency between each question

on the KSWAL-QOL. For test-retest reliability and convergent validity, Pearson

correlation coefficients between the two tests were used. For discriminant

validity and between-group homogeneity, one-way ANOVAs were used to test

differences between groups. In order to compare differences by category and

differences between diets, independent t tests were used.

- 33 -

Results

1. Development of the Korean SWAL-QOL

1.1. Assessing the appropriateness of the modified Korean SWAL-QOL questions

Quantitative results of the survey regarding the appropriateness of each

question are shown in Table 8.

The CVI for each question ranged between 0.53 and 1.00 with none of the

questions having a CVI value less than 0.50. Among the 44 questions, those

with low appropriateness included “need to remove a foreign object in the

throat by forcing a cough,” “spit out liquid in the throat that contains food or

saliva by coughing it out of the mouth,” and “almost never feel hungry.”

- 34 -

Table 8. Mean and CVI according to an modified K-SWAL-QOL (N=8)

Items M CVI

1 삼킴장애를 해결하는 것이 매우 어렵다 4.87 0.96

2 삼킴장애는 내 마음을 심란하게 한다 4.87 0.96

3 식사시간이 아주 오래 걸린다 4.87 0.96

4 다른 사람들보다 먹는데 오래 걸린다 4.12 0.78

5 배고픔을 거의 못 느낀다 3.25 0.56

6 음식을 먹든 못 먹든 큰 관심이 없다 4.12 0.78

7 더 이상 먹는 게 즐겁지 않다 5.00 1.00

8 기침 4.75 0.93

9 음식을 먹을 때 사레 걸림 4.87 0.96

10물(요플레, 점성 있는 액체, 묽은 죽같은 유동식)을 먹

을 때 사레 걸림4.87 0.96

11 진한 침 또는 점액질(가래)을 느낌 4.62 0.90

12 구역질 4.25 0.81

13 침 흘림 4.62 0.90

14 음식을 씹기가 어려움 5.00 1.00

15 과도한 침 또는 점액질(가래)이 있음 4.25 0.81

16 목구멍안의 이물질을 헛기침을 하여 제거해야 함 3.25 0.53

17 목구멍에 음식물이 끈적거림(들러붙음) 4.00 0.75

18 입안에 음식물이 들러붙음 3.62 0.65

19 입 밖으로 음식물이나 침(유동식)이 흘러나옴 4.50 0.87

20 코로 음식물이나 물(유동식)이 흘러나옴 4.62 0.90

21목안에 음식물이나 침을 포함한 액체가 있을 때 입 밖

으로 기침해서 뱉어냄3.12 0.53

22먹을 수 있는 음식과 먹을 수 없는 음식을 구별하는

것이 어렵다3.75 0.68

Note. CVI = content validity index; M = mean.

- 35 -

Table 8. Mean and CVI according to an modified K-SWAL-QOL (Contd.) (N=8)

Items M CVI

23 좋아하는 음식 중에 현재 먹을 수 있는 음식이 무엇인지 모르겠다 5.00 1.00

24 사람들은 내가 하는 말의 발음을 잘 알아듣지 못하거나 의미를 이해하지 못한다 5.00 1.00

25 명확하게 말하는 것이 어렵다 5.00 1.00

26 음식을 먹을 때 질식(음식물이 기도로 들어가서 숨을 쉴 수 없는 상태)될까봐 두렵다 4.75 0.93

27 폐렴이 걸릴까봐 걱정이다 3.87 0.71

28 물을 마실 때 질식할까봐 두렵다 3.87 0.71

29 음식물이 기도로 넘어가는지 식도로 넘어가는지 느낌을 잘 모르겠다 3.37 0.59

30 삼킴장애로 인해 우울하다 5.00 1.00

31 먹거나 마실 때 조심해야 한다는 것이 짜증난다 5.00 1.00

32 삼킴장애 때문에 의기소침해진다 5.00 1.00

33 삼킴장애 때문에 좌절감을 느낀다 5.00 1.00

34 삼킴장애를 가지고 살아가는 것이 점점 더 참을 수 없이 힘들다 5.00 1.00

35 삼킴장애 때문에 외식을 하지 않는다 5.00 1.00

36 삼킴장애 때문에 사회생활이 힘들다 5.00 1.00

37 삼킴장애로 인하여 일상생활과 여가 활동들이 변했다 5.00 1.00

38 삼킴장애 때문에 가족과 친구들 안에서의 내 역할이 변했다 4.75 0.93

39 삼킴장애 때문에 사교모임이 즐겁지 않다 5.00 1.00

40 신체적으로 쇠약함을 느낀다 4.62 0.90

41 지친다고 느낀다 3.62 0.62

42 피곤하다고 느낀다 3.62 0.62

43 잠이 들기까지 힘들다 3.87 0.71

44 잠을 자다가 중간에 깬다 3.87 0.71

Note. CVI = content validity index; M = mean.

- 36 -

2. Testing the Reliability of the Korean SWAL-QOL

2.1. Internal consistency

The Cronbach’s α for the total scale was 0.98 (Table 9). The Cronbach’s α

by category was 0.86 for general anxiety, 0.88 for eating duration, 0.83 for

appetite, 0.91 for swallowing disorder symptoms, 0.71 for food selection, 0.54

for communication, 0.91 for fear, 0.89 for mental health, 0.57 for social life,

0.80 for fatigue, and 0.72 for sleep (Table 10).

- 37 -

Table 9. The internal consistency of items in the K-SWAL-QOL (N=126)

Sub-scale ItemsCorrected item-total

correlationCronbach’s alpha if

item deletedBurden 1 .860 .979

2 .836 .979

Eating duration 3 .583 .980

4 .823 .979

Eating desire 5 .525 .980

6 .495 .980

7 .835 .979

Symptoms 8 .889 .979

9 .898 .979

10 .559 .980

11 .734 .979

12 .775 .979

13 .911 .979

14 .546 .980

15 .914 .979

16 .904 .979

17 .939 .979

18 .558 .980

19 .861 .979

20 .609 .980

21 .873 .979

Food selection 22 .776 .979

23 .602 .980

Note. K-SWAL-QOL = Korean Swallowing-Quality of Life Questionnaire.

- 38 -

Table 9. The internal consistency of items in the K-SWAL-QOL (Contd.)

Sub-scale ItemsCorrected item-total


item deleted

Communication 24 .578 .980

25 .476 .980

Fear 26 .894 .979

27 .712 .979

28 .833 .979

29 .868 .979

Mental health 30 .867 .979

31 .867 .979

32 .887 .979

33 .861 .979

34 .899 .979

Social functioning 35 .773 .979

36 .832 .979

37 .767 .979

38 .467 .983

39 .062 .981

fatigue 40 .616 .980

41 .775 .979

42 .813 .979

Sleep 43 .477 .980

44 .793 .979

Total .980


- 39 -

Table 10. The areal internal consistency in the K-SWAL-QOL (N=126)

Sub-scale Item numberCorrected item-total


item deletedBurden 2 .858 .851



Symptoms 14 .913 .917


communication 2 .542 .865

Fear 4 .911 .831



Fatigue 3 .800 .854

Sleep 2 .724 .858


- 40 -

2.2 Test-retest reliability

The Pearson's correlation coefficient (r) was calculated for two measurements

obtained from 20 patients over a 2-week interval to verify test-retest reliability.

The correlations between the two testing periods were high, ranging between

0.80-0.98 (p < .001; Table 11).

Table 11. The areal test-retest reliability in the K-SWAL-QOL (N=126)

Sub-scale Item numberPearson correlation

coefficient(r)p

Burden 2 .948 .000



Symptoms 14 .977 .000


communication 2 .800 .000

Fear 4 .952 .000



Fatigue 3 .866 .000

Sleep 2 .874 .000

Total 44 .981 .000


- 41 -

3. Validity Testing

3.1 Convergent validity

3.1.1 Convergent validity using the K-SWAL-QOL and K-WHOQOL-BREF

In order to verify convergent validity, the Pearson's correlation coefficient

between the K-SWAL-QOL and K-WHOQOL-BREF was calculated for the

patients with swallowing disorder. This correlation was statistically significant

(p < .001; Table 9). The correlations between each category of the

K-SWAL-QOL and K-WHOQOL-BREF were all statistically significant (p <

.05, p < .001; Table 12).

- 42 -

Table 12. The correlation between K-SWAL-QOL and K-WHOQOL-BREF (N=126)

Pearson correlation coefficient(r)

K-WHOQOL-BREF

overall QOL

physical health

domain

psychological

domain

social relations

hips domain

environmental domain

Total

K-SWAL-QOL

Burden .602** .684** .682** .575** .676** .732**

Eating duration .591** .695** .643** .561** .687** .725**

Eating desire .483** .616** .580** .510** .575** .632**

Symptoms .589** .779** .712** .659** .706** .788**

Food selection .453** .614** .577** .470** .518** .603**

communication .197* .340** .268** .260** .369** .341**

Fear .667** .803** .740** .716** .758** .835**

Mental health .623** .744** .725** .619** .685** .772**

Social functioning .236** .514** .447** .452** .408** .483**

Fatigue .461** .659** .541** .551** .559** .634**

Sleep .359** .554** .499** .471** .532** .562**

Total .612** .800** .738** .674** .734** .813**

Note. K-SWAL-QOL = Korean Swallowing-Quality of Life Questionnaire; K-WHOQOL-BREF = Korean version of the World Health Organization Quality of Life Instrument-Short Version.*p

- 43 -

3.1.2 Convergent validity using the K-SWAL-QOL and K-HDRS

In order to verify convergent validity, the Pearson's correlation coefficient

between the K-SWAL-QOL and K-HDRS was calculated for the patients of

swallowing disorder. This correlation was also statistically significant (p <

.001; Table 10). The correlation between each category of the K-SWAL-QOL

and K-HDRS were also statistically significant (p < .001; Table 13).

- 44 -

Table 13. The correlation between K-SWAL-QOL and K-HDRS (N=126)

구 분 Pearson correlation coefficient(r)

K-SWAL-QOL K-HDRS

Burden -.747**

Eating duration -.726**

Eating desire -.655**

Symptoms -.852**

Food selection -.606**

communication -.325**

Fear -.777**

Mental health -.709**

Social functioning -.639**

Fatigue -.625**

Sleep -.514**

Total -.831**

Note. K-SWAL-QOL = Korean Swallowing-Quality of Life Questionnaire; K-HDRS = Korean version of the Hamilton Rating Scale.*p

- 45 -

3.2. Discriminant Validity

3.2.1 Discriminant validity through comparison between normal subjects and

patients with swallowing disorders

In order to verify discriminant validity, independent t-tests were conducted

by category of the K-SWAL-QOL with normal subjects and patients with

swallowing disorders. Group differences were observed for all 11 categories (p

< .001).

As a result of analyzing discriminant load values in the structural matrix,

discriminating power was high with regard to general anxiety, fear, mental

health, swallowing disorder symptoms, social life, eating duration, fatigue,

appetite, sleep, food selection, and communication (Table 14).

- 46 -

Table 14. Comparison of the K-SWAL-QOL’s areal mean sore between swallow disorders and normal subjects (N=228)

Total

Swallow disorders(N=126)

Normal subjects(N=102)

t

M ± SD M ± SD

Burden 10 4.21±2.18 9.67±0.73 -26.321**

Eating duration 10 6.02±1.99 9.63±0.79 -18.57**

Eating desire 15 10.55±2.22 14.15±1.26 -15.35**

Symptoms 70 41.14±12.82 66.04±5.09 -19.93**

Food selection 10 7.51±2.02 9.33±1.01 -8.78**

communication 10 8.14±1.48 9.50±0.93 -8.07**

Fear 20 10.48±4.30 18.90±1.58 -20.32**

Mental health 25 12.63±5.73 23.63±2.00 -20.08**

Social functioning

25 12.53±2.65 19.62±2.77 -19.63**

Fatigue 15 6.36±2.02 10.81±1.75 -17.50**

Sleep 10 4.66±1.82 7.56±1.50 -12.89**

Total 220 124.27±34.29 198.91±13.09 -22.48**

Note. K-SWAL-QOL = Korean Swallowing-Quality of Life Questionnaire; M = mean; SD = standard deviation.**p

- 47 -

3.2.2. Discriminant validity depending on oral intake

Independent t tests were conducted by category to assess discriminant

validity based on oral intake. Group differences were observed for each

category except for “communication” (p < .001; Table 15).

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Table 15. Comparison of the K-SWAL-QOL’s areal mean sore depending on oral intake (N=126)

Total

Non-oral intake(N=22)

Oral intake(N=104) t

M ± SD M ± SD

Burden 10 2.09±0.24 4.66±2.14 -11.72**

Eating duration 10 3.81±1.62 6.49±1.74 -6.59**

Eating desire 15 8.45±2.44 11.00±1.91 -5.39**

Symptoms 70 21.90±7.33 45.21±9.64 -12.75**

Food selection 10 4.54±2.15 8.14±1.32 -7.54**

communication 10 6.90±2.52 8.40±1.00 -2.73

Fear 20 5.36±1.96 11.56±3.86 -10.98**

Mental health 25 6.63±2.76 13.90±5.38 -9.17**

Social functioning

25 8.90±1.47 13.29±2.17 -9.01**

Fatigue 15 4.27±1.31 6.80±1.86 -6.04**

Sleep 10 3.36±1.76 4.94±1.72 -3.89**

Total 220 76.27±19.16 134.43±27.49 -9.43**

Note. K-SWAL-QOL = Korean Swallowing-Quality of Life Questionnaire; M = mean; SD = standard deviation.**p

- 49 -

3.2.3. Validity of the K-SWAL-QOL depending on diet

One-way ANOVAs were conducted by category depending on the type of

diet among swallowing disorder patients. Group differences were observed for

all categories except for “social life” (p

- 50 -

Table 16. Comparison of the K-SWAL-QOL’s areal mean sore depending on diet (N=104)

Total

Pudding(N=40)

Finely chopped food

(N=32)

Soft-boilded rice

(N=32) F

M ± SD M ± SD M ± SD

Burden 10 2.75±0.89 4.68±1.67 7.03±0.96 111.69**

Eating duration 10 4.85±0.92 6.87±1.12 8.15±1.13 90.04**

Eating desire 15 9.45±1.25 11.12±1.56 12.81±1.09 58.45**

Symptoms 70 34.40±5.07 49.75±4.13 54.18±2.05 239.78**

Food selection 10 7.35±1.29 8.31±0.99 8.96±1.09 18.19**

communication 10 8.00±0.84 8.75±1.10 8.56±0.91 6.13*

Fear 20 7.50±2.38 13.00±1.90 15.21±1.23 152.77**

Mental health 25 9.65±3.99 13.62±4.26 19.50±1.54 69.35**

Social functioning 25 12.60±2.29 13.31±2.05 14.15±1.86 4.89

Fatigue 15 5.65±2.29 7.25±1.21 7.81±0.73 17.37**

Sleep 10 4.00±1.86 5.12±1.51 5.93±0.58 14.52**

Total 220 106.20±16.70 141.81±15.75 162.34±4.94 152.95**

Note. KSWAL-QOL = Korean Swallowing-Quality of Life Questionnaire; M = mean; SD = standard deviation.*p

- 51 -

4. Clinical Utility

The average for each item ranged between 3.60 and 4.52, while the highest

score was observed for the question, “Is there significance in the overall

swallowing treatment process based on the test results?” High scores were also

observed for the following two items: “Is it easy for patients to perform

(understand)?” and “Is it helpful in setting treatment goals?” (Table 17).

Table 17. Clinical Utility results of K-SWAL-QOL (N=30)

Survey item M±SD

Is it easy for patients to perform (understand)?” and “Is it helpful in setting treatment goals?

4.26±0.69

Is it useful to plan treatment goal? 4.23±0.62

Whether the patient is focused on? 4.13±0.77

Is it appropriated for evaluation time? 3.86±0.73

Is it easy to interpret the evaluation results? 4.06±0.82

Is it easy to evaluate tool clinically? 3.60±0.67

Is there significance in the overall swallowing treatment process based on the test results?

4.52±0.62

Note. K-SWAL-QOL = Korean Swallowing-Quality of Life Questionnaire; M = mean; SD = standard deviation.

- 52 -

Discussion

The current study involved creating a Korean translated version of the

SWAL-QOL. This was accomplished through a translation and back-translation

verification process in order to examine the feasibility of applying the

SWAL-QOL to Korean samples. In order to confirm the usefulness of the

translated tool, the study also verified its reliability, validity, and clinical utility

among normal subjects as well as patients with swallowing disorders.

The patient sample included stroke patients and patients with traumatic brain

injuries. This study was a bit different from previous studies (e.g., McHorney

et al., 2002) that included patients with various forms of brain damage as well

as head and neck cancer patients (109 subjects). However, 17% of patients

with swallowing disorders in the present study were tube-feeders, while the

percentage of tube-feeders in McHorney et al. (2002) was similar (15%).

While a study by Kim (2013) included patients with vascular diseases (28

subjects) as well as cancer patients (5 subjects), and other studies included

patients with other diseases such as head and neck cancer in addition to brain

damage, the current study only included patients with brain damage. When

selecting subjects with swallowing disorders, we excluded individuals with

decreased cognitive functioning using the same method as those used in both

- 53 -

Chinese and Dutch samples in order to obtain accurate survey results

(Nunnally & Bernstein, 1994).

The adaptation process for developing the Korean SWAL-QOL consisted of

four steps (translation, back-translation, assessment of the appropriateness of the

questions, and completion of the final Korean version of the SWAL-QOL).

When using an assessment tool developed in a particular culture and foreign

language in a different cultural setting, there are limitations to using

standardized scores, or the content may be inappropriate owing to cultural and

linguistic differences (Fiedler et al., 2011). Therefore, in order to reduce such

limitations, the current study performed the translation and back-translation

verification process used by Beaton et al. (2000). The presence of

inappropriate questions was tested by calculating the content validity index

(CVI); all sentences were found to be appropriate in this study with a CVI of

at least 0.50 for each item (Polit, Beck, & Owen, 2007; Shelley, 1984).

As a result of verifying internal consistency and test-retest reliability for the

K-SWAL-QOL, we observed Cronbach’s α values that ranged from 0.78-0.97.

Coefficients were high for general anxiety (.86), eating duration (.88), appetite

(.83), swallowing disorder symptoms (.91), fear (.91), mental health (.89),

fatigue (.80), food selection (.71) and sleep (.72). In particular, swallowing

disorder symptoms showed the highest internal consistency with 0.91.

McHorney et al. observed Cronbach’s α values less than 0.8 for fear (0.79),

- 54 -

0.80-0.89 for 6 categories, and greater than 0.9 for the other categories

(McHorney et al., 2000). Coefficient values were between 0.68 and 0.94 in a

Swedish study, between 0.51 and 0.95 and 0.60 and 0.92 in two Dutch

studies, between 0.61 and 0.97 in a French study, greater than 0.7 in a

Chinese study, and Kim (2013) reported a value of 0.95 (Bogaardt et al.,

2009; McHorney et al., 2002; Vanderwegen, Van Nuffelen, De Bodt, 2013;

Finizia et al., 2012). The results of the current study also revealed similarities

with results from previous studies. In other words, this measure adequately

describes swallowing disorder symptoms within patient groups. In contrast,

results of the internal consistency analysis showed low values for

communication (.54) and social life (.57). These reliability values could be low

because there were not many questions for communication (Vanderwegen, Van

Nuffelen, & De Bodt, 2013) or it could have been because good swallowing

ability cannot be directly translated into good communication skills (Scorense,

Brown, Logemann, Wilson, & Hemdon, 1994). The reason for the low value

for social life could have been that individuals with swallowing disorders have

a fear of socializing with others, but there could be people who do not

particularly fear socializing with others despite having a swallowing disorder

(Ekberg, Hamdy, Woisard, Wuttge–Hannig, & Ortega, 2002).

In general, test-retest reliability is considered high when the coefficient is

greater than 0.75 (Lee, 2007). The Pearson correlation coefficient for test-retest

- 55 -

reliability in terms of total scores in the present study was 0.98, and all

categories had statistically significant correlations (0.80-0.98). Our values were

higher than those observed in other studies: McHorney et al. (0.59 and 0.91);

Swedish study (0.75 and 0.96); Chinese study (0.60 and 0.83); Dutch studies

(0.50 and 0.91). These results reflect the fact that the same administrator

conducted an interview-format survey assessment in order to reduce error

(Nunnally & Bernstein, 1994).

In terms of convergent validity, the correlation between the total

K-SWAL-QOL scores and K-WHOQOL-BREF scores was statistically

significant. Correlations with all categories were also significant, with values

ranging between 0.20 and 0.84. The categories “physical health” from the

K-WHOQOL-BREF and “swallowing disorder symptoms” from the

K-SWAL-QOL, which reflect functional level, had the highest correlations.

These seem to reflect the physical aspects of swallowing disorders the best. In

addition, statistically significant, negative correlations were found between the

total K-SWAL-QOL scores and K-HDRS scores (ranged between 0.33 and

0.83). The highest correlation was for swallowing disorder symptoms, which

indicates that swallowing disorders are related to patients’ quality of life, in

line with results reporting that quality of life is lower due to severe

swallowing disorder symptoms (Vanderwegen, Van Nuffelen, & De Bodt,

2013).

- 56 -

A discriminant validity analysis with normal subjects and patients with

swallowing disorders for each category of the K-SWAL-QOL revealed

significant group differences. This shows that the assessment tool clearly

discriminates between normal subjects and patients with swallowing disorders.

These results are similar to those from Kim (2013). In addition, the findings

replicate those of studies conducted abroad (e.g., McHorney et al., 2002). The

lowest score difference was seen for “communication,” which might be because

there are patients with swallowing disorders who have difficulties with

communication due to aphasia and dysarthria. On the other hand, some

patients have good pronunciation and verbal expression, in spite of several

problems related to the bronchial apparatus.

Results of another discriminant validity verification showed significant

differences between tube-feeders and non-tube feeders except for the

“communication” category. This might be interpreted as patients with

swallowing disorders who do not feed through a tube have a better quality of

life than those who do. In other words, as swallowing function increases,

quality of life related to swallowing increases (McHorney et al., 2002). The

fact that a significant difference was not found for the “communication”

category indicates that while food cannot be ingested orally, the same results

were obtained among Dutch samples. Additionally, the lack of a significant

difference could be because verbal problems do not necessarily overlap with

- 57 -

swallowing problems in patients with swallowing disorders.

Finally, results of a discriminant validity analysis depending on type of diet

showed significant differences for all categories of the K-SWAL-QOL except

for “social life.” The reason for this could be because differences between

those who focus on ingesting food and those who enjoy conversing and

communicating, rather than eating per se, while socially engaging with others.

When examining the clinical utility of this measurement tool, we observed

that the mean of each item from the K-SWAL-QOL ranged between 3.62 and

4.52, indicating that the scale was easy to use, takes sufficient time to

administer, and is helpful for understanding useful clinical information (Law et

al., 1990). The highest score was found for “Is there significance in the

overall swallowing treatment process based on the test results?” followed by

“Is it easy for patients to perform (understand)?” and “Is it helpful in setting

treatment goals?” These results indicate that the K-SWAL-QOL is meaningful

in terms of assessing quality of life in the swallowing treatment process since

it requires addressing quality of life along with functional aspects when setting

treatment goals. The self-report format also makes it easy to perform this

measure, and patients are better able to understand it.

As the current study only included brain-damaged patients, it is necessary to

include various patient samples such as central nervous system patients,

degenerative disease patients, and cancer patients.

- 58 -

Despite these limitations, the K-SWAL-QOL provided several improvements

to previous studies assessing quality of life among patients with swallowing

disorders. As most of the present subjects had brain damage, this assessment

tool was particularly appropriate for this patient sample. What differentiates

this study from others is the fact that we assessed the appropriateness of the

questions. Additionally, validity was established by conducting discriminant

validity verification depending on oral intake and type of diet, and convergent

validity was obtained through a depression scale. Finally, surveying clinical

utility of the completed K-SWAL-QOL was accomplished by involving

occupational therapists that frequently treat swallowing disorders. In the future,

this scale should be a useful tool for providing intervention through an

appropriate assessment of swallowing disorder patients in the areas of

occupational therapy and rehabilitation.

- 59 -

Conclusion

The purpose of the present study was to examine the usefulness of creating

a Korean version of the SWAL-QOL, which measures quality of life related to

swallowing, by assessing its reliability and validity.

The translation process for this measure involved correcting inappropriate

vocabulary through translation, modifying sentences with errors in meaning

through back-translation, and completing the final Korean version by assessing

the appropriateness of the questions.

The Cronbach’s α and Pearson's correlation coefficients (r) for test-retest

reliability ranged between 0.54-0.91 and 0.80-0.98, respectively. For convergent

validity, a significant correlation (p < .001) was observed for all categories on

comparing the K-WHOQOL-BREF and K-HDRS. Results of discriminant

validity showed a significant difference between patients with swallowing

disorders and normal subjects for all categories of the K-SWAL-QOL (p <

.001) as well as differences based on diet and feeding type (p < .001). A test

of clinical utility revealed significant results regarding the use of this measure

for clinical assessment and treatment of swallowing disorders.

The K-SWAL-QOL is able to assess several aspects of quality of life

related to swallowing. The K-SWAL-QOL appears to be a reliable and valid

- 60 -

assessment tool. In the future, this measure should be used as a means of

providing appropriate intervention for occupational therapy and rehabilitation.

- 61 -

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