Journal of Surgical Oncology 2015;112:93–97
Cross-Cultural Adaptation and Validation of the Korean Toronto Extremity Salvage Score for Extremity Sarcoma HAN-SOO KIM, MD, PhD, JIYEON YUN,
BS,
SEUNGCHEOL KANG, MD,
AND
ILKYU HAN, MD, PhD*
Department of Orthopaedic Surgery, Seoul National University Hospital, Seoul, Korea
Background: A Korean version of Toronto Extremity Salvage Score (TESS), a widely used disease-specific patient-reported questionnaire for assessing physical function of sarcoma patients, has not been developed. Objectives: 1) to translate and cross-culturally adapt the TESS into Korean, and 2) to examine its comprehensibility, reliability and validity. Methods: TESS was translated into Korean, then translated back into English, and reviewed by a committee to develop the consensus version of the Korean TESS. The Korean TESS was administered to 126 patients to examine its comprehensibility, reliability, and validity. Results: Comprehensibility was high, as the patients rated questions as “easy” or “very easy” in 96% for the TESS lower extremity (LE) and in 97% for the TESS upper extremity (UE). Test-retest reliability with intraclass coefficient (0.874 for LE and 0.979 for UE) and internal consistency with Cronbach’s alpha (0.978 for LE and 0.989 for UE) were excellent. Korean TESS correlated with the MSTS score (r ¼ 0.772 for LE and r ¼ 0.635 for UE), and physical functioning domain of EORTC-CLQ C30 (r ¼ 0.840 for LE and r ¼ 0.630 for UE). Conclusion: Our study suggests that Korean version of the TESS is a comprehensible, reliable, and valid instrument to measure patient-reported functional outcome in patients with extremity sarcoma.
J. Surg. Oncol. 2015;112:93–97. © 2015 Wiley Periodicals, Inc.
KEY WORDS: TESS; extremity; sarcoma; function; patient-reported
INTRODUCTION Because of the significant impact of extremity sarcoma surgery on the patients’ function, patient’s function after surgery is recognized as an important outcome measure in addition to the oncological outcome in extremity sarcoma [1]. For proper assessment of function in extremity sarcoma, a disease-specific measure rather than a generic measure is preferred, as patients who undergo surgery for extremity sarcoma show a wide spectrum of function based on patients’ age, tumor type, the extent and type of tissue resected, adjuvant treatment and reconstruction methods [2,3]. Moreover, measures that reflect the patient’s perception rather that of the clinician is desirable [4]. Thus, a disease-specific patient-oriented measure is needed to assess physical function in extremity sarcoma. Toronto Extremity Salvage Score (TESS) is a disease-specific patientreported questionnaire developed for assessing physical function of patients undergoing surgery for extremity sarcoma [5]. The content of the TESS was developed by patient and clinician input, and includes the types of functional difficulties experienced by extremity sarcoma patients. The questions of the TESS include activities such as body movement, mobility, self-care, and performing daily tasks. TESS was developed in English and has been used in various studies regarding surgery for extremity sarcoma [5]. However, in order to use an English questionnaire in non-English speaking countries, the questionnaire needs to undergo a process of crosscultural validation in terms of its ability to take into account culturespecific conditions prior to their administration [6,7]. Moreover, given the need for multinational studies for rare cancers such as a sarcoma, multiple language versions of the validated questionnaires are needed for standardization of study outcome measurements. To date, TESS exists in an English [5], Portuguese [8], and Danish version [9], but a Korean version had not been developed and validated. The aims of this study were (i) to translate and cross-culturally adapt the TESS into Korean, and (ii) to examine the comprehensibility,
ß 2015 Wiley Periodicals, Inc.
reliability and validity of the Korean version of TESS for use in patients with extremity sarcoma.
MATERIALS AND METHODS Patients Patients who visited our outpatient clinic between March 2014 and November 2014 were asked to participate in the study, if they met the following criteria at the time of the visit; (i) underwent curative surgery for histologically confirmed extremity sarcoma, (ii) age over 18 years, (iii) at least 12 months after last surgery, and (iv) without complications related to surgery. Of the 129 patients who were eligible, 3 refused, and 126 patients participated in the study (Table I). Medical records were reviewed for the following clinical data: patients’ age, sex, anatomical location of the tumor, histological type, date of surgery, and type of surgery. Institutional Review Board approval was obtained and informed consent was received from all participants for this study. The mean age at the time of administration of the TESS questionnaire was 47 years (range, 18–80 years). The most common histological types were liposarcoma (n ¼ 13) and undifferentiated pleomorphic sarcoma (UPS, n ¼ 10) for soft tissue sarcoma, osteosarcoma (n ¼ 32) and chondrosarcoma (n¼19) for bone
Funding sources: No specific funding was disclosed. Disclosure: The authors declare that they have nothing to disclose. *Correspondence to: Ilkyu Han, MD, PhD, Department of Orthopaedic Surgery, Seoul National University Hospital, 101 Daehak-ro Jongno-gu, Seoul 110-744, Korea. Fax: þ82-2-764-2718. E-mail: [email protected] Received 9 February 2015; Accepted 27 May 2015 DOI 10.1002/jso.23947 Published online 12 June 2015 in Wiley Online Library (wileyonlinelibrary.com).
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TABLE I. Patient Characteristics Characteristic Age (years) Sex Female Male Time from surgery (months) Tissue type Soft tissue sarcoma Bone sarcoma Histological type Osteosarcoma Chondrosarcoma Liposarcoma UPS Synovial sarcoma Myxofibrosarcoma Fibrosarcoma UPS of bone Leiomyosarcoma Epithelioid sarcoma Clear cell sarcoma Extraskeletal chondrosarcoma Ewing’s sarcoma Others Location Knee Thigh Pelvis/Hip Shoulder Lower leg Upper arm Ankle/Foot Forearm/Wrist Elbow Bone resection Not done Done Limb salvage status Limb salvage Amputation TESS MSTS EORTC QLQ-C30 Physical functioning Role functioning Social functioning Quality of life
Lower extremity (n ¼ 92)
Upper extremity (n ¼ 34)
Overall (n ¼ 126)
46.7 (18.4)
48.9 (17.1)
47.3 (18.0)
38 (41%) 54 (59%) 46.3 (40.1)
16 (41%) 20 (59%) 46.3 (30.1)
52 (41%) 74 (59%) 46.3 (38.0)
49 (53%) 43 (47%)
15 (44%) 19 (56%)
64 (51%) 62 (49%)
28 5 11 7 8 5 4 4 2 1 2 2 2 11
(30%) (6%) (12%) (8%) (9%) (6%) (4%) (4%) (2%) (1%) (2%) (2%) (2%) (12%)
4 (12%) 14 (41%) 2 (6%) 3 (9%) 0 (0%) 2 (6%) 3 (9%) 0 (0%) 1 (2%) 2 (6%) 0 (0%) 0 (0%) 0 (0%) 3 (9%)
32 (25%) 19 (16%) 13 (10%) 10 (9%) 8 (7%) 7 (6%) 7 (6%) 4 (3%) 3 (2%) 3 (2%) 2 (1%) 2 (1%) 2 (1%) 14 (11%)
27 26 20 0 11 0 8 0 0
(29%) (28%) (22%) (0%) (12%) (0%) (9%) (0%) (0%)
0 (0%) 0 (0%) 0 (0%) 12 (47%) 0 (0%) 11 (32%) 0 (0%) 6 (18%) 1 (3%)
27 (21%) 26 (21%) 20 (16%) 12 (13%) 11 (9%) 11 (9%) 8 (6%) 6 (4%) 1 (1%)
46 (50%) 46 (50%)
21 (62%) 13 (38%)
67 (53%) 59 (47%)
88 (96%) 4 (4%) 80.0 (20.3) 22.7 (6.1)
32 (94%) 2 (6%) 88.9 (21.1) 24.9 (5.5)
120 (95%) 6 (5%) 82.4 (20.8) 23.3 (6.1)
73.7 70.8 76.4 65.7
83.9 79.4 80.4 68.6
76.5 73.2 77.5 66.5
(22.1) (29.1) (28.3) (26.3)
(20.7) (29.2) (29.5) (29.3)
(22.1) (29.3) (28.5) (27.1)
UPS, undifferentiated pleomorphic sarcoma; TESS, Toronto Extremity Salvage Score; MSTS, Musculoskeletal Tumor Society Rating Scale; EORTC, European Organisation for Research and Treatment of Cancer; QLQ-C30, quality of life questionnaire core 30.
sarcoma. Of the 34 upper extremity patients, dominant side was involved in 14 patients (42%). The mean time from the last surgery to the questionnaire was 46 months (range, 13–112).
TESS Questionnaire TESS questionnaire consists of a lower extremity and an upper extremity version with 30 and 29 questions respectively [5]. The questions encompass activities of daily living such as working, mobility and leisure. Each question is rated on 5-point scale of “impossible to do,” “extremely difficult,” “moderately difficult,” “a little bit difficult,” or “not at all difficult”. There is the option of selecting “This task is not applicable for me”, when the question is not a usual activity for the participant. The total score can range from 0 to 100, with higher scores indicating better function.
bilingual translators whose mother tongue was Korean independently translated the original version of the TESS questionnaire. The two versions were analyzed and merged by the translators and orthopedic surgeons who specialize in extremity sarcoma (I. Han and S. Kang) after a consensus was reached. The consensus version was backtranslated into English independently by two bilingual translators who had not participated in the forward translation. All versions of the translation were analyzed by the review committee, which was made up of the 4 translators, 2 orthopedic surgeons (I. Han and S. Kang), and a Korean professional translator. The committee evaluated semantic, idiomatic, and conceptual equivalence of all items and answers. All elements of the questionnaire were analyzed, and discrepancies between members were discussed until consensus was reached.
Comprehensibility Translation of TESS The translation and cross-cultural adaptation of the Korean version of TESS followed the guidelines suggested by Beaton et al [6]. Two Journal of Surgical Oncology
Of the 126 patients, the first 34 consecutive patients were asked to rate each question with regard to whether they understood and were familiar with the task described in reflecting one’s function on a 4-point scale
Validation of the Korean Version of the TESS
95
To examine the test–retest reliability, the first 34 consecutive patients were asked to answer the same TESS questionnaire again one week after the first visit. Of the 34 patients, 20 patients returned the second questionnaire and was used for analysis. The first questionnaire was completed while visiting the clinic and the second one was done by mail one week after the first visit. Internal consistency was calculated to measure to what extent items of a questionnaire represent common underlying task.
were 80.0 (range, 30–100) and 88.9 (rang, 9–100), respectively (Table I). For the TESS upper extremity, the average score of the 29 items was 4.56 (range, 4.09–4.79). Lifting a box to an overhead shelf was the item with the lowest score and was rated as “extremely difficult”, “impossible to do” or “moderately difficult” in 8 of 34 patients (24%). Participating in my usual sports activities (24%) and gardening or yard work (6%) and were most frequently chosen as “not applicable.” For the TESS lower extremity, the average score of the 30 items was 4.19 (range, 2.97–4.67). Kneeling was the item with the lowest score and was rated as “extremely difficult”, “impossible to do” or “moderately difficult” in 54 of 92 patients (53%). Participating in sexual activities (25%) and driving (24%) were most frequently chosen as “not applicable.”
Validity
Comprehensibility
Construct validity measures the extent to which scores of the TESS questionnaire relate to other widely accepted measures in theoretically related or unrelated concepts. As TESS was developed as a measure of physical function, construct validity was assessed by comparing the response on TESS questionnaire and two widely used measures; (i) Musculoskeletal Tumor Society Rating Scale (MSTS) [10], and (ii) functional and quality of life scales of the Quality of Life Questionnaire Core 30 of European Organization for Research and Treatment of Cancer (EORTC QLQ-C30) [11]. MSTS is the most widely used physician reported functional score for extremity sarcoma patients [1,10]. EORTC QLQ-C30 is a widely used measure of function and quality of life in cancer patients [11], and has been validated in Korean [12]. Among the functional scales of EORTC QLQ-C30, the following scales were used in this study; physical functioning (PF), role functioning (RF), social functioning (SF) and quality of life (QoL). Descriptive analyses were used to examine the ability of the TESS to demonstrate different levels of scores according to the anticipated profile of disabilities. Patents were analyzed according to the following criteria: (i) sarcoma tissue type (soft tissue sarcoma or bone sarcoma); (ii) performance of bone resection as part of the surgery; and (iii) limb salvage status (limb salvage or amputation).
Patients’ comprehensibility was of the TESS questionnaire high, with 87–100% (mean: 96%) in the TESS lower extremity and 83–100% (mean: 97%) in the TESS upper extremity rating questions as “easy” or “very easy.” “Kneeling is’ in the lower extremity TESS, and “Completing my usual duties at work” and “Working my usual number of hours is” in the upper extremity TESS, were the least comprehensible questions.
(1: difficult; 2: moderate; 3: easy; 4: very easy). The questions were regarded as comprehensible when patients answered scale of 3 or above.
Reliability
Reliability: Test–Retest Reliability The test-retest reliability showed good reliability with ICCs of 0.874 for the lower extremity TESS and 0.979 for the upper extremity TESS (Table II). The Bland-Altman plot showed no systematic bias (Fig. 1).
Reliability: Internal Consistency Cronbach’s alphas showed strong reliability with standardized alphas of 0.978 for the lower extremity TESS and 0.989 for the upper extremity TESS (Table II). The Spearman rank correlation coefficients between one item and the total score (excluding that item) were from 0.582 to 0.888 in the lower extremity TESS and from 0.654 to 0.976 in the upper extremity TESS.
Validity
Statistics Test–retest reliability was assessed using intraclass correlation coefficient (ICC). To show the absolute differences and limits of agreement between the test- and the retest data, Bland and Altman plots, describing the mean scores of the two assessments and differences between them, were used for visual representation of the test–retest data [13]. Internal consistency was measured by Cronbach’s alpha, which provides a measurement of the strength of the relationship among the questions of the questionnaire. A Cronbach’s alpha 0.80 was considered acceptable [14]. Construct validity was assessed by calculating the Spearman rank correlation coefficients between the TESS and either the EORTC QLQ-C30 or the MSTS. Strength of agreement for the correlation coefficient and the ICC was expressed as follows: strong (0.70), moderate (>0.5 to
Cross-Cultural Adaptation and Validation of the Korean Toronto Extremity Salvage Score for Extremity Sarcoma HAN-SOO KIM, MD, PhD, JIYEON YUN,
BS,
SEUNGCHEOL KANG, MD,
AND
ILKYU HAN, MD, PhD*
Department of Orthopaedic Surgery, Seoul National University Hospital, Seoul, Korea
Background: A Korean version of Toronto Extremity Salvage Score (TESS), a widely used disease-specific patient-reported questionnaire for assessing physical function of sarcoma patients, has not been developed. Objectives: 1) to translate and cross-culturally adapt the TESS into Korean, and 2) to examine its comprehensibility, reliability and validity. Methods: TESS was translated into Korean, then translated back into English, and reviewed by a committee to develop the consensus version of the Korean TESS. The Korean TESS was administered to 126 patients to examine its comprehensibility, reliability, and validity. Results: Comprehensibility was high, as the patients rated questions as “easy” or “very easy” in 96% for the TESS lower extremity (LE) and in 97% for the TESS upper extremity (UE). Test-retest reliability with intraclass coefficient (0.874 for LE and 0.979 for UE) and internal consistency with Cronbach’s alpha (0.978 for LE and 0.989 for UE) were excellent. Korean TESS correlated with the MSTS score (r ¼ 0.772 for LE and r ¼ 0.635 for UE), and physical functioning domain of EORTC-CLQ C30 (r ¼ 0.840 for LE and r ¼ 0.630 for UE). Conclusion: Our study suggests that Korean version of the TESS is a comprehensible, reliable, and valid instrument to measure patient-reported functional outcome in patients with extremity sarcoma.
J. Surg. Oncol. 2015;112:93–97. © 2015 Wiley Periodicals, Inc.
KEY WORDS: TESS; extremity; sarcoma; function; patient-reported
INTRODUCTION Because of the significant impact of extremity sarcoma surgery on the patients’ function, patient’s function after surgery is recognized as an important outcome measure in addition to the oncological outcome in extremity sarcoma [1]. For proper assessment of function in extremity sarcoma, a disease-specific measure rather than a generic measure is preferred, as patients who undergo surgery for extremity sarcoma show a wide spectrum of function based on patients’ age, tumor type, the extent and type of tissue resected, adjuvant treatment and reconstruction methods [2,3]. Moreover, measures that reflect the patient’s perception rather that of the clinician is desirable [4]. Thus, a disease-specific patient-oriented measure is needed to assess physical function in extremity sarcoma. Toronto Extremity Salvage Score (TESS) is a disease-specific patientreported questionnaire developed for assessing physical function of patients undergoing surgery for extremity sarcoma [5]. The content of the TESS was developed by patient and clinician input, and includes the types of functional difficulties experienced by extremity sarcoma patients. The questions of the TESS include activities such as body movement, mobility, self-care, and performing daily tasks. TESS was developed in English and has been used in various studies regarding surgery for extremity sarcoma [5]. However, in order to use an English questionnaire in non-English speaking countries, the questionnaire needs to undergo a process of crosscultural validation in terms of its ability to take into account culturespecific conditions prior to their administration [6,7]. Moreover, given the need for multinational studies for rare cancers such as a sarcoma, multiple language versions of the validated questionnaires are needed for standardization of study outcome measurements. To date, TESS exists in an English [5], Portuguese [8], and Danish version [9], but a Korean version had not been developed and validated. The aims of this study were (i) to translate and cross-culturally adapt the TESS into Korean, and (ii) to examine the comprehensibility,
ß 2015 Wiley Periodicals, Inc.
reliability and validity of the Korean version of TESS for use in patients with extremity sarcoma.
MATERIALS AND METHODS Patients Patients who visited our outpatient clinic between March 2014 and November 2014 were asked to participate in the study, if they met the following criteria at the time of the visit; (i) underwent curative surgery for histologically confirmed extremity sarcoma, (ii) age over 18 years, (iii) at least 12 months after last surgery, and (iv) without complications related to surgery. Of the 129 patients who were eligible, 3 refused, and 126 patients participated in the study (Table I). Medical records were reviewed for the following clinical data: patients’ age, sex, anatomical location of the tumor, histological type, date of surgery, and type of surgery. Institutional Review Board approval was obtained and informed consent was received from all participants for this study. The mean age at the time of administration of the TESS questionnaire was 47 years (range, 18–80 years). The most common histological types were liposarcoma (n ¼ 13) and undifferentiated pleomorphic sarcoma (UPS, n ¼ 10) for soft tissue sarcoma, osteosarcoma (n ¼ 32) and chondrosarcoma (n¼19) for bone
Funding sources: No specific funding was disclosed. Disclosure: The authors declare that they have nothing to disclose. *Correspondence to: Ilkyu Han, MD, PhD, Department of Orthopaedic Surgery, Seoul National University Hospital, 101 Daehak-ro Jongno-gu, Seoul 110-744, Korea. Fax: þ82-2-764-2718. E-mail: [email protected] Received 9 February 2015; Accepted 27 May 2015 DOI 10.1002/jso.23947 Published online 12 June 2015 in Wiley Online Library (wileyonlinelibrary.com).
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Kim et al.
TABLE I. Patient Characteristics Characteristic Age (years) Sex Female Male Time from surgery (months) Tissue type Soft tissue sarcoma Bone sarcoma Histological type Osteosarcoma Chondrosarcoma Liposarcoma UPS Synovial sarcoma Myxofibrosarcoma Fibrosarcoma UPS of bone Leiomyosarcoma Epithelioid sarcoma Clear cell sarcoma Extraskeletal chondrosarcoma Ewing’s sarcoma Others Location Knee Thigh Pelvis/Hip Shoulder Lower leg Upper arm Ankle/Foot Forearm/Wrist Elbow Bone resection Not done Done Limb salvage status Limb salvage Amputation TESS MSTS EORTC QLQ-C30 Physical functioning Role functioning Social functioning Quality of life
Lower extremity (n ¼ 92)
Upper extremity (n ¼ 34)
Overall (n ¼ 126)
46.7 (18.4)
48.9 (17.1)
47.3 (18.0)
38 (41%) 54 (59%) 46.3 (40.1)
16 (41%) 20 (59%) 46.3 (30.1)
52 (41%) 74 (59%) 46.3 (38.0)
49 (53%) 43 (47%)
15 (44%) 19 (56%)
64 (51%) 62 (49%)
28 5 11 7 8 5 4 4 2 1 2 2 2 11
(30%) (6%) (12%) (8%) (9%) (6%) (4%) (4%) (2%) (1%) (2%) (2%) (2%) (12%)
4 (12%) 14 (41%) 2 (6%) 3 (9%) 0 (0%) 2 (6%) 3 (9%) 0 (0%) 1 (2%) 2 (6%) 0 (0%) 0 (0%) 0 (0%) 3 (9%)
32 (25%) 19 (16%) 13 (10%) 10 (9%) 8 (7%) 7 (6%) 7 (6%) 4 (3%) 3 (2%) 3 (2%) 2 (1%) 2 (1%) 2 (1%) 14 (11%)
27 26 20 0 11 0 8 0 0
(29%) (28%) (22%) (0%) (12%) (0%) (9%) (0%) (0%)
0 (0%) 0 (0%) 0 (0%) 12 (47%) 0 (0%) 11 (32%) 0 (0%) 6 (18%) 1 (3%)
27 (21%) 26 (21%) 20 (16%) 12 (13%) 11 (9%) 11 (9%) 8 (6%) 6 (4%) 1 (1%)
46 (50%) 46 (50%)
21 (62%) 13 (38%)
67 (53%) 59 (47%)
88 (96%) 4 (4%) 80.0 (20.3) 22.7 (6.1)
32 (94%) 2 (6%) 88.9 (21.1) 24.9 (5.5)
120 (95%) 6 (5%) 82.4 (20.8) 23.3 (6.1)
73.7 70.8 76.4 65.7
83.9 79.4 80.4 68.6
76.5 73.2 77.5 66.5
(22.1) (29.1) (28.3) (26.3)
(20.7) (29.2) (29.5) (29.3)
(22.1) (29.3) (28.5) (27.1)
UPS, undifferentiated pleomorphic sarcoma; TESS, Toronto Extremity Salvage Score; MSTS, Musculoskeletal Tumor Society Rating Scale; EORTC, European Organisation for Research and Treatment of Cancer; QLQ-C30, quality of life questionnaire core 30.
sarcoma. Of the 34 upper extremity patients, dominant side was involved in 14 patients (42%). The mean time from the last surgery to the questionnaire was 46 months (range, 13–112).
TESS Questionnaire TESS questionnaire consists of a lower extremity and an upper extremity version with 30 and 29 questions respectively [5]. The questions encompass activities of daily living such as working, mobility and leisure. Each question is rated on 5-point scale of “impossible to do,” “extremely difficult,” “moderately difficult,” “a little bit difficult,” or “not at all difficult”. There is the option of selecting “This task is not applicable for me”, when the question is not a usual activity for the participant. The total score can range from 0 to 100, with higher scores indicating better function.
bilingual translators whose mother tongue was Korean independently translated the original version of the TESS questionnaire. The two versions were analyzed and merged by the translators and orthopedic surgeons who specialize in extremity sarcoma (I. Han and S. Kang) after a consensus was reached. The consensus version was backtranslated into English independently by two bilingual translators who had not participated in the forward translation. All versions of the translation were analyzed by the review committee, which was made up of the 4 translators, 2 orthopedic surgeons (I. Han and S. Kang), and a Korean professional translator. The committee evaluated semantic, idiomatic, and conceptual equivalence of all items and answers. All elements of the questionnaire were analyzed, and discrepancies between members were discussed until consensus was reached.
Comprehensibility Translation of TESS The translation and cross-cultural adaptation of the Korean version of TESS followed the guidelines suggested by Beaton et al [6]. Two Journal of Surgical Oncology
Of the 126 patients, the first 34 consecutive patients were asked to rate each question with regard to whether they understood and were familiar with the task described in reflecting one’s function on a 4-point scale
Validation of the Korean Version of the TESS
95
To examine the test–retest reliability, the first 34 consecutive patients were asked to answer the same TESS questionnaire again one week after the first visit. Of the 34 patients, 20 patients returned the second questionnaire and was used for analysis. The first questionnaire was completed while visiting the clinic and the second one was done by mail one week after the first visit. Internal consistency was calculated to measure to what extent items of a questionnaire represent common underlying task.
were 80.0 (range, 30–100) and 88.9 (rang, 9–100), respectively (Table I). For the TESS upper extremity, the average score of the 29 items was 4.56 (range, 4.09–4.79). Lifting a box to an overhead shelf was the item with the lowest score and was rated as “extremely difficult”, “impossible to do” or “moderately difficult” in 8 of 34 patients (24%). Participating in my usual sports activities (24%) and gardening or yard work (6%) and were most frequently chosen as “not applicable.” For the TESS lower extremity, the average score of the 30 items was 4.19 (range, 2.97–4.67). Kneeling was the item with the lowest score and was rated as “extremely difficult”, “impossible to do” or “moderately difficult” in 54 of 92 patients (53%). Participating in sexual activities (25%) and driving (24%) were most frequently chosen as “not applicable.”
Validity
Comprehensibility
Construct validity measures the extent to which scores of the TESS questionnaire relate to other widely accepted measures in theoretically related or unrelated concepts. As TESS was developed as a measure of physical function, construct validity was assessed by comparing the response on TESS questionnaire and two widely used measures; (i) Musculoskeletal Tumor Society Rating Scale (MSTS) [10], and (ii) functional and quality of life scales of the Quality of Life Questionnaire Core 30 of European Organization for Research and Treatment of Cancer (EORTC QLQ-C30) [11]. MSTS is the most widely used physician reported functional score for extremity sarcoma patients [1,10]. EORTC QLQ-C30 is a widely used measure of function and quality of life in cancer patients [11], and has been validated in Korean [12]. Among the functional scales of EORTC QLQ-C30, the following scales were used in this study; physical functioning (PF), role functioning (RF), social functioning (SF) and quality of life (QoL). Descriptive analyses were used to examine the ability of the TESS to demonstrate different levels of scores according to the anticipated profile of disabilities. Patents were analyzed according to the following criteria: (i) sarcoma tissue type (soft tissue sarcoma or bone sarcoma); (ii) performance of bone resection as part of the surgery; and (iii) limb salvage status (limb salvage or amputation).
Patients’ comprehensibility was of the TESS questionnaire high, with 87–100% (mean: 96%) in the TESS lower extremity and 83–100% (mean: 97%) in the TESS upper extremity rating questions as “easy” or “very easy.” “Kneeling is’ in the lower extremity TESS, and “Completing my usual duties at work” and “Working my usual number of hours is” in the upper extremity TESS, were the least comprehensible questions.
(1: difficult; 2: moderate; 3: easy; 4: very easy). The questions were regarded as comprehensible when patients answered scale of 3 or above.
Reliability
Reliability: Test–Retest Reliability The test-retest reliability showed good reliability with ICCs of 0.874 for the lower extremity TESS and 0.979 for the upper extremity TESS (Table II). The Bland-Altman plot showed no systematic bias (Fig. 1).
Reliability: Internal Consistency Cronbach’s alphas showed strong reliability with standardized alphas of 0.978 for the lower extremity TESS and 0.989 for the upper extremity TESS (Table II). The Spearman rank correlation coefficients between one item and the total score (excluding that item) were from 0.582 to 0.888 in the lower extremity TESS and from 0.654 to 0.976 in the upper extremity TESS.
Validity
Statistics Test–retest reliability was assessed using intraclass correlation coefficient (ICC). To show the absolute differences and limits of agreement between the test- and the retest data, Bland and Altman plots, describing the mean scores of the two assessments and differences between them, were used for visual representation of the test–retest data [13]. Internal consistency was measured by Cronbach’s alpha, which provides a measurement of the strength of the relationship among the questions of the questionnaire. A Cronbach’s alpha 0.80 was considered acceptable [14]. Construct validity was assessed by calculating the Spearman rank correlation coefficients between the TESS and either the EORTC QLQ-C30 or the MSTS. Strength of agreement for the correlation coefficient and the ICC was expressed as follows: strong (0.70), moderate (>0.5 to
