Validation Study of the Korean Version of the Brief Fatigue Inventory

Transcription

1 Vol. 29 No. 2 February 2005 Journal of Pain and Symptom Management 165 Original Article Validation Study of the Korean Version of the Brief Fatigue Inventory Young Ho Yun, MD, PhD, Xin Shelley Wang, MD, Jung Suk Lee, RN, MSN, Ju Won Roh, MD, PhD, Chang Geol Lee, MD, Won Sup Lee, MD, PhD, Keun Seok Lee, MD, Soo-Mee Bang, MD, Tito R. Mendoza, PhD, and Charles S. Cleeland, PhD Quality of Cancer Care Branch (Y.H.Y., J.S.L.) and Uterine Cancer Branch (J.W.R.), Research Institute and Hospital, National Cancer Center, Goyang, Gyeonggi, Korea; Department of Symptom Research (X.S.W., T.R.M., C.S.C), University of Texas M. D. Anderson Cancer Center, Houston, Texas, USA; Department of Radiation Oncology (C.G.L.), Yonsei University College of Medicine, Yonsei Cancer Center, Seoul, Korea; Department of Internal Medicine (W.S.L.), Gyeong-Sang National University Hospital, Jinju, South Kyongsang, Korea; Department of Internal Medicine (K.S.L.), Hallym University Kangdong Sacred Heart Hospital, Seoul, Korea; and Department of Internal Medicine (S.-M.B.), Gachon Medical School, Ghil Medical Center, Incheon, Korea Abstract The goal of this study was to evaluate the reliability and validity of the Korean version of the Brief Fatigue Inventory (BFI-K). One hundred seventy-eight cancer patients and the same number of age- and sex-matched control subjects completed the BFI-K, the European Organization for Research and Treatment of Cancer QLQ-C30 (EORTC QLQ-C30), the Beck Depression Inventory (BDI), and a Brief Pain Inventory (BPI). The Cronbach s alpha coefficient for the BFI-K was in the cancer patient group and in the control group. The global score and nine of the single item scores for the BFI-K were significantly correlated with the fatigue and global health status/qol subscale of the EORTC QLQ-C30, BDI, and BPI (coefficient range ). Discriminant validity showed that BFI-K could distinguish significant differences of performance status between subgroups of patients, and between the cancer patient group and the control group, as expected. Our study has shown that the BFI-K is a reliable, valid self-rating instrument in terms of its psychometric properties. J Pain Symptom Manage 2005;29: U.S. Cancer Pain Relief Committee. Published by Elsevier Inc. All rights reserved. Key Words Cancer, fatigue, assessment, validation, Korea Address reprint requests to: Young Ho Yun, MD, PhD, Quality of Cancer Care Branch, Research Institute and Hospital, National Cancer Center, 809 Madudong, Ilsan-gu, Goyang, Gyeonggi, , Korea. Accepted for publication: April 29, U.S. Cancer Pain Relief Committee Published by Elsevier Inc. All rights reserved. Introduction Fatigue is among the most frequently reported and most distressing symptoms experienced by cancer patients. 1 3 Fatigue adversely affects quality of life and is commonly associated with depression. 4,5 Fatigue has a negative impact on return to work for many people with /05/$ see front matter doi: /j.jpainsymman

2 166 Yun et al. Vol. 29 No. 2 February 2005 cancer, 5,6 and not being able to return to work following an illness frequently results in financial losses and social isolation. 5 It is not clear how preexisting health conditions, direct effects of cancer, and cancer treatment interact to produce or exacerbate fatigue. In the literature, some mechanisms that may be responsible for fatigue include sleep disturbances, various biochemical changes secondary to disease and treatment, psychosocial factors, internal and external environmental conditions, level of activity, nutritional status, and diverse inherent factors. 7 Similar to pain assessment, the Fatigue Practice Guidelines panel noted that clinicians must rely on patients selfreports of their fatigue levels and associated distress for measuring fatigue. 3 Despite its high prevalence and its effects on quality of life, fatigue has not been measured routinely in patients with cancer and is not readily discussed between the physician and the patient. 2,8 If fatigue management in cancer patients is to be improved, it is necessary to obtain data on fatigue prevalence, severity, and impact on quality of life. It is also necessary to be able to document the effectiveness of various treatments, educational programs, and policy changes that intend to improve fatigue management. Several self-rating instruments have been developed for the assessment of fatigue, such as the Multidimensional Fatigue Inventory (MFI), Functional Assessment of Cancer Therapy-Fatigue (FACT-F), Fatigue Symptom Inventory, and Piper Fatigue Scale. 6 These multidimensional instruments assess different aspects of fatigue, but are too long for exhausted patients to complete. Some instruments depend on English-based expressions or idioms that make them difficult to translate. 2 The Brief Fatigue Inventory (BFI) 2 was developed by the Department of Symptom Research to measure fatigue in cancer populations and to determine how much the disease and treatment influence fatigue. There is an increasing need to assess the fatigue experienced by patients as a result of cancer and its treatment in Korea, but no easily administered instrument has been available. The goal of this study was to create a Korean version of the Brief Fatigue Inventory for Korean cancer patients, and thus produce an instrument that is sensitive, reliable and valid for use in future clinical trials assessing fatigue in Korea. Methods Patients, Normal Subjects, and Data Collection Patient samples for this study were recruited at five hospitals in Korea. All patients had a pathological diagnosis of cancer, were older than 18 years, gave their informed consent to participate, and were able to understand and complete the questionnaires. The patients were asked to complete the self-administered questionnaires either at outpatient clinic or during their hospitalization. A comparison group was similarly recruited from age- and sex-matched normal subjects who visited the Center for Cancer Screening in the Department of Cancer PreventionintheKoreanNationalCancerCenter. They met eligible criteria but were not diagnosed with a pathology of cancer. The study was approved by the Institutional Review Board of the National Cancer Center, Korea, and The University of Texas M. D. Anderson Cancer Center. Measures Both cancer patients and control group subjects completed the following questionnaires: Brief Fatigue Inventory (BFI). The BFI consists of 9 items on a single page. Fatigue and its interference are measured on numeric scales from There are three items asking subjects to describe their fatigue now, at its usual level, and at its worst level during the previous 24 hours, using extreme points no fatigue and fatigue as bad as you can imagine. The next six items describe how much fatigue has interfered with aspects of their life during the previous 24 hours. Specifically, these items are general activity, mood, walking ability, normal work (both work outside the home and daily chores), relations with other people, and enjoyment of life. These interference scales range from 0 ( does not interfere ) to 10 ( completely interferes ). The global score for the BFI is calculated as the mean value of these 9 items. The validity and reliability of the original BFI has been established. 2 Similar to pain assessment, fatigue severity can be categorized as

3 Vol. 29 No. 2 February 2005 Validation of the Korean Version of the BFI 167 mild, moderate, or severe: 1 3 for mild, 4 6 for moderate, and 7 10 for severe fatigue. 2,6 The Korean version of the BFI was developed using the forward backward translation process. In the translation process, the items were first translated into Korean by one translator whose native language was Korean and then back-translated into English by a second translator at M. D. Anderson whose native language was English, and who had not seen the original English version. Bilingual fluency was required of both translators to complete the translation. Next, the English back-translated items were compared with the original. If a back-translated item did not agree with the original, the first translator performed a second translation and the second translator performed a second backtranslation. This process was repeated until agreement was reached. European Organization for Research and Treatment of Cancer QLQ-C30 (EORTC QLQ-C30; version 3.0). The EORTC QLQ-C30 is a 30-item, cancer-specific questionnaire-integrating system for assessing the health-related quality of life (QOL) of cancer patients. 9 The questionnaire incorporates five functional scales (physical, role, cognitive, emotional, and social), three symptom scales (fatigue, pain, and nausea and vomiting), a global health and QOL scale, and single items for the assessment of additional symptoms commonly reported by cancer patients (e.g., dyspnea, appetite loss, sleep disturbance, constipation, and diarrhea), as well as the perceived financial impact of the disease and treatment. 10 The Korean version of the EORTC QLQ-C30 has now been validated. 11 Beck Depression Inventory (BDI). The Beck Depression Inventory (BDI) was originally designed to measure the depth or intensity of depression in psychiatric patients. The BDI evaluates 21 symptoms of depression 14 cognitive-affective symptoms and seven somatic symptoms. Each symptom is rated on a 4-point intensity scale and scores are added to give a total ranging from 0 to 63; higher scores represent more severe depression. 12,13 The Korean version of the BDI has been validated previously. 14 Brief Pain Inventory (BPI). The BPI is an instrument for evaluating pain that can measure the intensity of pain and the interference of pain with the patient s life. The BPI uses 11-point numeric rating scales (NRS), with pain intensity ranging from 0 ( no pain ) to 10 ( pain as bad as you can imagine ). Because pain due to cancer can be quite variable during the course of the day, the BPI ask patients to rate their pain intensity at the time of responding to the questionnaire (pain now), and also at its worst, least, and average over the previous week. The ratings can also be made for the last 24 hours depending on the design of the study. The BPI also asks patients to rate, using the same type of NRS, how their pain interferes with their general activity, mood, walking, work, sleep, relations with others, and enjoyment of life. First developed in English, the BPI has been widely used in many countries, and the Korean version has now been validated. 15 Sociodemographic Information. The patient s and normal subject s age, sex, education level, job status, marital status, and religious type were obtained using a self-administrated questionnaire. Patient Data Checklist. The patient s medical information was obtained from their medical records, which included disease information (cancer site and stage, disease status). Additionally, their performance status, as defined by the Eastern Cooperative Oncology Group (ECOG), was clinically evaluated on the same day as assessment by attending clinicians. Statistical Analysis We used descriptive statistics to describe how patients rate fatigue severity and interference with function. Internal consistency reliability was assessed using Cronbach s coefficient alpha. A low alpha value suggests that some items either have very high variability or that the items are not all measuring the same thing. Construct validity was determined using factor analysis that reproduced the same factor loading pattern seen in the original scale. 16 Concurrent validity was evaluated by calculating the Pearson s correlation coefficient between the BFI-K and the EORTC QLQ-C30 Fatigue subscale and global health status/qol subscale, BPI and BDI scales. Discriminant validity was examined by comparing the BFI-K scores in patients having different ECOG performance statuses; it was hypothesized that patients

4 168 Yun et al. Vol. 29 No. 2 February 2005 having poor performance status have an increased level of fatigue severity and interference. Finally, the method of patient-normal subject comparison was used to evaluate discriminant validity of the BFI-K. A t-test was used to test for statistically significance of group differences in the BFI-K item scores. Results Sample Characteristics Two hundred twelve cancer patients gave their consent and participated in this study. Thirty-four of these cancer patients were not able to complete the questionnaires. The most common reason given was a lack of time. The mean time needed for completion of the BFI-K, EORTC QLQ-C30, BDI, and BPI questionnaires was approximately 20 minutes. For data analysis, 178 cancer patients (84%) and the same number of control subjects, who matched by age and sex, were included. The demographic and clinical characteristics of the samples are shown in Table 1. The subjects in the cancer patient group had a lower education level (P 0.001) and less full-time jobs (P 0.001), and were less likely to be married (P 0.001) than those in the control group. Nineteen percent (19%) of the cancer patients had a poor functional status (a score of 2 or higher on ECOG PS scale). Additionally, according to the results of the worst fatigue item on the BFI-K, fatigue was present in 165 (92.7%) cancer patients and 163 (91.6%) control group members, and 38.2% and 38.3% of these subjects, respectively, experienced severe fatigue ( 7 on scale of 0 10). Missing Rate We found that there were no missing responses to the first question of the BFI-K, which asked whether the subject had unusual fatigue in the last week. There were a total of 16 missing responses for the other nine questions combined, 3 responses in the cancer patient group and 13 in the control group. Thus, missing Table 1 Sociodemographic and Clinical Characteristics of Study Subjects Cancer Patient Group (n 178) Control Group (n 178) Characteristic No. % No. % P-value Age, years Mean SD Sex Male Education Completed high school Occupation Employed full-time Homemaker Retired Disabled due to illness Other Marital status Married Disease type Lung Head and neck Cervix Stomach Colon/rectum Leukemia Others ECOG PS a (0) Fully active (1) Restricted but ambulatory (2) Ambulatory, capable of self care (3) Capable of only limited self care (4) Completely disabled a ECOG PS Eastern Cooperative Oncology Group Performance Status.

5 Vol. 29 No. 2 February 2005 Validation of the Korean Version of the BFI 169 rates were 0.2% of the total data points (178 patients answering 9 items) in the cancer patient group, and 1.0% in the control group. Because all individuals responded to the majority of the items (at least five items on the BFI-K), all of the collected data were included in this analysis. 17 Reliability Reliability in each group was equally high. The Cronbach s alpha coefficient for the BFI-K was calculated as in the cancer patient group and in the control group. Cronbach s alpha coefficients for all nine items, if individual items were deleted, are listed in Table 2. Construct Validity Construct validity was confirmed by factor analysis. The factor loadings in each group were equally high, ranging from 0.76 for enjoyment of life to 0.90 for activity and mood in the cancer patient group and from 0.72 for relation to others to 0.92 for mood in the control group. These patterns of factor loadings in both groups indicated the association of the nine BFI-K items with a single factor. The results of the scree tests for the BFI-K suggested a 1-factor solution with eigenvalue over 1 in both the cancer patient group and the control group, and the first factors of both groups explained 72.9% and 73.6% of the variability in the data, respectively (Table 3). Concurrent Validity The concurrent validity of the BFI-K in the cancer patient group was demonstrated by calculating the correlations between the global Table 2 Reliability with Cronbach s Alpha and Alpha If Item Deleted Cancer Patient Control Group Group (n 178) (n 178) Alpha Alpha if item deleted Fatigue right now Usual fatigue Worst fatigue Activity Mood Walking Working Relation to others Enjoyment of life Table 3 Factor Analysis, Principal Axis Solution Cancer Patient Control Group Group (n 178) (n 178) Factor Factor Fatigue right now Usual fatigue Worst fatigue Activity Mood Walking Working Relation to others Enjoyment of life Eigenvalue Proportion score and 9 of the single-item scores of the BFI-K and the EORTC QLQ-C30 fatigue subscale, which measures fatigue and was previously validated (Table 4). Global and nine of the single-item scores for the BFI-K were significantly correlated with the EORTC QLQ-C30 fatigue subscale (P ), with correlation coefficients ranging from 0.50 to The global score had the highest correlation coefficient among the BFI-K scores. For evaluation of concurrent validity, correlation coefficients between the global score and nine of the single-item scores of the BFI-K and quality of life, depression level, pain severity, and interference were also assessed in the cancer patient group (Table 4). Three previously validated measures, EORTC QLQ-C30 global health status/qol subscale, BDI, and BPI, were used in this analysis. The global score and nine of the single-item scores for the BFI-K had significantly moderate correlation coefficients with all other measures (P ). Discriminant Validity Discriminant validity was examined in the cancer patient group by comparing the BFI-K item scores of groups with different ECOG performance status scores. Patients with different ECOG scores were expected to vary by the severity and interference of fatigue. As expected, patients with more severe disease had higher levels of fatigue. Table 5 shows that patients having a poor performance status (a score of 2 or higher on the ECOG PS scale) had significantly higher BFI-K scores than did those having a good status (P 0.05 to P ). We also investigated the differences in BFI-K scores between the cancer patient group and

6 170 Yun et al. Vol. 29 No. 2 February 2005 Table 4 Pearson s Correlation Coefficients Among EORTC QLQ C30, BDI, BPI, and Items in the Standard Korean Version of the BFI (Patients, n 178) Global Now Usual Worst Activity Mood Walking Working Relation Enjoyment Score EORTC QLQ - C30 Global health status/qol Fatigue BDI BPI severity BPI interference EORTC QLQ-C30 European Organization for Research and Treatment of Cancer QLQ-C30; BDI Beck Depression Inventory; BPI Brief Pain Inventory; BFI Brief Fatigue Inventory. Significant correlation P for all the values. control group. Patients having a cancer diagnosis were expected to have higher levels of fatigue. The present results showed significant differences between the cancer patient and control groups for the mean scores of both fatigue severity (4.7 vs. 3.9, P 0.01) and interference (4.3 vs. 2.7, P ). With the exception of the worst fatigue item, the cancer patient group had significantly higher BFI-K scores than the control group on all items (P 0.01, Table 6). Figure 1 presents a graph of the mean BFI- K interference score (composite of six items) against fatigue severity as measured by the worst fatigue item. This plot shows that cancer patients experienced more severe interference (higher interference scores) than control group members with same score for the worst fatigue item. Discussion This study showed that the Korean version of the BFI exhibited a satisfactory psychometric analysis. The internal consistency was very high. In terms of the known-group comparison, the validity of the BFI-K was confirmed by the significant correlation between most of its scales and the BDI, subscale of BPI, Fatigue subscale, and global health status/qol subscale of EORTC QLQ-C30. The problems with the translation, as well as cultural differences in the concepts associated with fatigue, may have led to differences in the validation of the Korean as compared to the original version. However, translation of the BFI into Korean was simple and straightforward. In particular, the minimum number of missing value rates proved that the scale is easy to administer. As seen in the original and Japanese versions of the BFI, the factor solution for the Korean version produced one factor with an eigenvalue over one; similar to the original version, all items loaded on a single factor. Therefore, using a total BFI score with the mean of all nine items should be appropriate for the Korean version as well. The global score of BFI-K showed more significant correlation coefficients with BDI, BPI, global health status/qol subscale, and Fatigue subscale of EORTC QLQ-C30 than did either the worst, now, or usual Table 5 Comparisons of the BFI-K Item Scores by the ECOG PS a (Patients, n l78) ECOG PS 0-1 (n l44) ECOG PS 2-4 (n 34) Scales/Items Mean (SD) Mean (SD) P Fatigue right now 4.22 (2.61) 5.50 (2.92) 0.05 Usual fatigue 4.14 (2.55) 5.74 (2.70) 0.01 Worst fatigue 4.76 (2.75) 6.29 (2.89) 0.01 Activity 3.80 (2.62) 5.97 (3.21) Mood 3.86 (2.55) 5.76 (3.04) Walking 3.80 (2.82) 6.32 (3.62) Working 3.81 (2.78) 5.79 (3.61) 0.01 Relation to others 3.44 (2.83) 6.32 (3.19) Enjoyment of life 4.45 (2.84) 7.15 (3.17) a A lower ECOG PS score represents a better performance status.

7 Vol. 29 No. 2 February 2005 Validation of the Korean Version of the BFI 171 Table 6 Comparisons of the BFI-K Item Scores between the Cancer Patient Group and Control Group Cancer Patients Group (n 178) Control Group (n 178) Scales/Items Mean SD Mean SD P Fatigue right now Usual fatigue Worst fatigue Activity Mood Walking Working Relation to others Enjoyment of life fatigue item. This may indicate that the global score has better stability than do single-item scores. 6 With concurrent validity, comparison with the Fatigue subscale of EORTC QLQ-C30 showed a significant but moderate level of the correlation on fatigue item, similar to the previous Japan study. 6 The reason for moderate correlation may be that whereas the Fatigue subscale of EORTC QLQ-C30 asks patients experience or frequency of symptom like Did you need rest? or Were you tired?, the BFI asks severity and interference of patients fatigue. The analysis revealed that patients who were more ill (poor ECOG performance status) reported higher levels of fatigue, demonstrating discriminant validity. In comparison with the normal group, the cancer patient group showed higher scores of all items except the worst fatigue item. Unexpectedly, the presence of fatigue was common in the normal subjects in this study, and they also experienced severe fatigue, based on the worst fatigue item. It is possible that the normal group included patients with chronic fatigue syndrome or chronic illness other than cancer, and thus they might have exhibited a level of fatigue higher than the norm. However, cancer patients showed more severe interference (higher interference scores) than normal subjects with the same score on the worst fatigue (Figure 1). In fact, the fatigue reported by cancer patients is usually described as an unusual, excessive, whole-body experience and is different from fatigue in non-cancer. The high prevalence of fatigue in our study confirmed that fatigue is endemic in those with cancer and is among the most frequent symptoms found in cancer patients (84% of the patients). This finding is similar to a study with 1000 patients in a palliative care program. 4 According to the fatigue classification described in the original BFI, 38.2% of patients in the present study experienced severe fatigue, which was 7 or greater on a 0 10 scale of worst fatigue item. To improve the management of cancer-related fatigue, most health care professionals working in oncology should be familiar with patients who are totally disabled by their fatigue. The standards recommend that evaluation and documentation for the presence and severity of fatigue occur at the patient s initial contact with an oncology care provider, at appropriate Fig. 1. Plot of mean BFI-K interference items (composite of six interference items) against fatigue severity measured by Fatigue worst on BFI-K.

8 172 Yun et al. Vol. 29 No. 2 February 2005 intervals, and at all stages of disease when clinically indicated, during and following treatment. 3 In addition, a detailed assessment of fatigue is necessary to evaluate the effectiveness of different therapeutic regimens or to compare the side effects of different drugs such as opioids or antidepressants. 4 Our validation study had several limitations. First, it was not conducted as a comparison with community norms, but used hospital controls. Hospital controls have relatively severe fatigue, and the cancer patients and controls did not significantly differ on the worst fatigue item. Second, the sensitivity to the changes in fatigue of the BFI-K was not investigated. Further studies of these points are needed. Though our study enrolled cancer patients with variable status, including terminal cancer patients, research is needed with the BFI-K in palliative care patients with far advanced incurable disease. 4 In conclusion, our study has shown that the BFI-K is a reliable, valid self-rating instrument in terms of its psychometric properties, and is suitable for measuring the fatigue of cancer patients in Korea. This simple and easily administered measurement of fatigue is essential for studies of its prevalence, severity, impact on quality of life, and for studies of effectiveness of fatigue management in Korea. In clinical practice, the use of the BFI-K may minimize some of the barriers that exist in the typical communication between patient and physicians and nurses concerning fatigue in Korea. Acknowledgments This work was supported by National Cancer Center Grant The authors sincerely thank the cancer patients and the control group members who cooperated so willingly. References 1. Blesch KS, Paice JA, Wickham R, et al. Correlates of fatigue in people with breast or lung cancer. Oncol Nurs Forum 1991;18: Mendoza TR, Wang XS, Cleeland CS, et al. The rapid assessment of fatigue severity in cancer patients: use of the Brief Fatigue Inventory. Cancer 1999;85: Mock V. Fatigue management evidence and guidelines for practice. Cancer 2001;92: Radbruch L, Sabatowski R, Elsner F, et al. Validation of the German version of the Brief Fatigue Inventory. J Pain Symptom Manage 2003;25: Spelten ER, Verbeek JH, Uitterhoeve AL, et al. Cancer, fatigue and the return of patients to work a prospective cohort study. Eur J Cancer 2003;39: Okuyama T, Wang XS, Akechi T, et al. Validation study of the Japanese version of the brief fatigue inventory. J Pain Symptom Manage 2003;25: Nail L, Winningham M. Cancer nursing: principles and practice, Boston: Jones & Bartlett, Carmen PE, Tejpal G, Beth AJ, et al. A fatigue clinic in a comprehensive cancer center design and experiences. Cancer 2001;92: Fayer P, Aaronson NK, Bjordal K, et al. EORTC QLQ-C30 Scoring Manual. Brussels, Belgium: EORTC Quality of Life Group, Aaronson NK, Ahmedzai S, Bergman B, et al. The European Organization for Research and Treatment of Cancer QLQ-C30: A quality-of-life instrument for use in international clinical trials in oncology. J Natl Cancer Inst 1993;85: Yun YH, Park YS, Lee ES, et al. Validation of the Korean version of the EORTC QLQ-C30. Quality of Life Res, 2004;13: Bech P. Rating scales for affective disorders: their validity and consistency. Acta Psychiatr Scand 1981; 295(Suppl): Beck AT. The Beck Depression Inventory. In: McDowell I, Newell C, eds. Measuring health: A guide to rating scales and questionnaires. 2nd ed. New York: Oxford University Press, 1996: Hahn HM, Yum TH, Shin YW, et al. A standardization study of the Beck Depression Inventory in Korea. J Korean Neuropsychiatric Assn 1986;25: Yun YH, Mendoza T, Heo DS, et al. Development of cancer pain assessment tool in Korea: A validation study of a Korean version of the Brief Pain Inventory (BPI-K). Oncology 2004;66: Harman HH. Modern factor analysis, 2nd ed. Chicago: University of Chicago Press, Ware JE, Snow KK, Kosinski M, et al. SF-36 health survey manual and interpretation guide, Boston, MA: Nimrod Press, 1993.