PSYCHOMETRIC ASSESSMENT OF THE CHINESE LANGUAGE VERSION OF THE ST. GEORGE S RESPIRATORY QUESTIONNAIRE IN TAIWANESE PATIENTS WITH BRONCHIAL ASTHMA

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1 St. George's Respiratory Questionnaire PSYCHOMETRIC ASSESSMENT OF THE CHINESE LANGUAGE VERSION OF THE ST. GEORGE S RESPIRATORY QUESTIONNAIRE IN TAIWANESE PATIENTS WITH BRONCHIAL ASTHMA Kwua-Yun Wang, Chi-Hue Chiang, 1 Suh-Hwa Maa, 2 Wen-Yi Shau, 3 and Yen-Huei Tarn 4 Background and purpose: The St. George s Respiratory Questionnaire (SGRQ) is a disease-specific quality-of-life instrument. It was designed to measure quality of life in obstructive pulmonary disease, and its reliability and validity have been demonstrated in different language versions. The purpose of this study was to determine the psychometric properties of a Chinese language version of the SGRQ in Taiwanese asthma patients. Methods: A convenient sample of 124 asthma patients were recruited from the outpatient asthma clinic of a teaching hospital in the Taipei area. The inclusion criteria were outpatient, coherent, and a clinical diagnosis of asthma. Patients with additional medical conditions considered to impact the quality of life were excluded. Three component scores (symptoms, activity, and impacts) and a total score were calculated to assess the SGRQ s psychometric characteristics. Data including demographic characteristics, history of emergency visits and hospital admissions, asthma severity, and quality of life were collected by questionnaires. Cronbach s formula for the α-coefficient was used to estimate the internal consistency and reliability of the SGRQ. Pearson s product-moment correlation was used to estimate the concurrent validity of the SGRQ. The discriminating validity of the SGRQ was determined by the t-test for independent samples. Results: Results showed that the SGRQ was internally consistent, and had good content and face validity. The SGRQ total score was significantly correlated with both the Health Index and the RAND 36-item Health Survey (p < 0.05). The SGRQ discriminated patients with respect to asthma severity (p < 0.001), history of prior emergency visits (p < 0.05), and history of prior hospital admissions (p < 0.05). Conclusions: This study demonstrated that the Chinese language version of the SGRQ has internal consistency and validity with strong evidence of content, concurrent, and discriminating validity in Taiwanese asthma patients. These findings suggest that it is a useful measure of quality of life in Taiwanese asthma patients. (J Formos Med Assoc 2001;100:455 60) Key words: psychometric assessment asthma questionnaire The St. George s Respiratory Questionnaire (SGRQ) is a disease-specific quality-of-life instrument designed for use in patients with asthma and chronic obstructive pulmonary disease (COPD) [1]. It focuses on the patient s view of factors related to the disease that significantly influence quality of life, and this approach may enhance the questionnaire s sensitivity to small changes in health status. If quality-of-life measures are to have clinical usefulness, they must reliably describe the patient population and respond to change [2]. The validity of different language versions of the SGRQ as a disease-related quality-of-life measure has been dem- School of Nursing, National Defense Medical Center; 1 Pulmonary Division, Tri-Service General Hospital, National Defense Medical Center; 2 School of Nursing, Chang-Gung University; 3 Graduate Institute of Clinical Medicine, College of Medicine, National Taiwan University; and 4 School of Pharmacy, National Defense Medical Center. Received: 5 January Revised: 5 March Accepted: 17 April Reprint requests and correspondence to: Dr. Kwua-Yun Wang, 10 Alley 175, Lane 75, Kangning Road, Section 3, Taipei, Taiwan. J Formos Med Assoc 2001 Vol 100 No 7 455

2 K.Y. Wang, C.H. Chiang, S.H. Maa, et al onstrated in several studies [1, 3 7]. However, its validity in Taiwanese patients has not been determined. The purpose of this study was to determine the psychometric properties of a Chinese language version of the SGRQ in Taiwanese asthma patients. 456 Materials and Methods The Chinese language version of the SGRQ contains 50 items and each item in the questionnaire has an empirically derived weight. Each score ranges from 0 to 100, where 100 indicates the worst health. A higher score indicates a worse outcome. The SGRQ was translated using a back-translation procedure [8, 9]. The first half of the SGRQ was translated by an attending physician at the Department of Chest Medicine, Chang Gung Memorial Hospital, and the second half was translated by the investigator. The investigator and the attending physician then translated each other s section back into English. After discussion of the items that did not seem equivalent in either English or Chinese, adjustments were made, and the translation process was repeated until the investigator and the attending physician were satisfied with the equivalent forms. The translation was then sent to two Chinese- American professionals in biochemistry and public health for validation. According to their comments, only minor modifications to a couple of sentences were made. Patients To gather data on the psychometric characteristics of the SGRQ, a cross-sectional survey of asthma patients was conducted. The inclusion criteria were as follows: outpatient, coherent, understanding of Chinese or Taiwanese, asthma diagnosis made by a pulmonary specialist, and consent to participation. Patients with additional medical conditions considered to impact the quality of life were excluded. Written informed consent was obtained prior to the start of the study and confidentiality of responses was assured. Approval of the study was obtained from the Human Subjects Committee of Tri-Service General Hospital. One hundred and twenty-four patients were recruited from this hospital outpatient asthma clinic by convenience sampling during a 1-month period (February 2000). Patients who met the study criteria were approached individually. In order to increase inter-rater reliability, before data collection was initiated, standardized procedures were established to ensure that data collectors (clinical nurses) used the same methods, style of presentation, and explanations. The patients were read the questionnaire and self-completion was supervised. Measures The variables analyzed in this study were history of emergency visits and hospital admissions, asthma severity, and quality of life. According to the Expert Panel Report II, asthma is defined as a chronic inflammatory disorder of the airways [10]. Asthma severity was categorized according to the recommendations of the Expert Panel Report II, which relies on an assessment of asthma symptoms during the day, nocturnal asthma symptoms, and physiologic measures of lung function (forced expiratory volume in 1 second, FEV 1, or peak expiratory flow rate, PEFR) [10]. Asthma severity was categorized into four grades: mild intermittent, mild persistent, moderate persistent, and severe persistent. The presence of one of the features of severity is sufficient to place a patient in the related category. The patient should be assigned to the most severe grade in which any feature occurs. The performance of the Chinese language version of the SGRQ was compared with two generic instruments: the RAND 36-item Health Survey and the Health Index [11]. The Health Index is an instrument in which an individual s overall health status is described by a single score on a continuum, from 0 (worst health) to 1 (perfect health). All patients were asked to recall what chest trouble they had experienced during the previous 4 weeks and its effect on daily life. The RAND 36-item Health Survey is a multi-item scale that covers nine health concepts. The nine health component scores were transformed linearly to scales of 0 to 100; a higher score indicated a more favorable health state. The psychometric characteristics of the Chinese language versions of the RAND 36-item Health Survey and the Health Index were previously reported by Tarn [11]. The RAND 36-item Health Survey showed acceptable internal consistency and reliability ranging from 0.50 to 0.85 and 0.67 to 0.88 in two previous studies [11, 12]. The internal consistency and reliability for the instrument in the present study was 0.72 to The content validity of the SGRQ was verified by a panel of five experts. Each item was rated on a scale of 1 to 5, with 5 indicating the highest applicability. The average score for each item was more than 4. To reduce ambiguity and assure clarity in the items, five adult asthma patients with different educational backgrounds completed the questionnaire and were questioned about their understanding of the item meanings. Concurrent validity of the SGRQ was evaluated by correlating the scores with two existing measures (RAND 36-item Health Survey, and Health Index) that assess health status in a manner consistent with the SGRQ. Finally, the discriminating validity of the SGRQ was assessed. Results were compared for patients whose asthma severity categorizations were mild intermittent J Formos Med Assoc 2001 Vol 100 No 7

3 St. George's Respiratory Questionnaire and mild persistent with those whose categorizations were moderate persistent and severe persistent. It was expected that patients in these categories would score differently on the SGRQ. In addition, this test compared patients who had previous emergency visits and hospital admissions with those who had no history of emergency room visits and hospital admissions. It was also expected that these patients would score differently on the SGRQ. Analysis Cronbach s formula for the α-coefficient was used to estimate the internal consistency and reliability for the entire SGRQ and for each subscale. Pearson s productmoment correlation was used to estimate the relationship between the SGRQ and the RAND 36-item Health Survey and Health Index scores. Relationships between the SGRQ and asthma severity, history of emergency visits, and history of hospital admissions were also tested. Discriminant validity was tested using the independent-samples t-test and the equal or unequal variance was computed based on results of the Levene s test. A p value of less than 0.05 was considered statistically significant. Results The sample comprised 64 men and 60 women aged from 18 to 79 years (mean 44.9 years). Asthma severity categorization showed that 43 (34.7%) had mild intermittent asthma, 11 (8.9%) had mild persistent asthma, 50 (40.3%) had moderate persistent asthma, and 19 (15.3%) had severe persistent asthma. The demographic data for the sample are summarized in Table 1. The SGRQ was considered by the assessors to have good content and face validity in terms of average score for each item and clarity in the items. The internal consistency and reliability estimates for the three subscales were symptoms 0.82, activity 0.88, and impacts 0.87, with a total α-coefficient of Pearson s correlation coefficients between the measures of concurrent validity and the SGRQ, subscales, and total scale score are shown in Table 2. All correlations except one between an SGRQ subscale and the RAND 36-item Health Survey were statistically significant. Table 3 shows the results for discriminating validity. Patients whose asthma severity was mild intermittent and mild persistent had significantly lower scores on the SGRQ total score and each of the three subscales than those with an asthma severity of moderate persistent or severe persistent. All subscales discriminated Table 1. Demographic characteristics of 124 patients with asthma Characteristic n (%) Gender Male 64 (51.6) Female 60 (48.4) Marital status Married 84 (67.7) Single 34 (27.4) Widowed 3 (2.4) Separated 3 (2.4) Level of education High school 68 (54.8) > High school 56 (45.2) Religion Buddhism 64 (51.6) No religion 36 (29.0) Other (eg, Catholic, Christian) 24 (19.4) Employment Full 57 (46.0) Other (eg, part-time, retired) 67 (54.0) Smoking status Never smoked 91 (73.4) Past smoker 16 (12.9) Current smoker 17 (13.7) Duration of disease 10 yr 69 (55.6) > 10 yr 55 (44.4) Allergy status Yes 91 (73.4) No 32 (26.6) between patients with an FEV 1 of less than or greater than 80%. There were significant differences in SGRQ total score and each of the three subscales between patients who had previous emergency visits or hospital admissions and those who had no such history. Discussion The SGRQ was designed to quantify the impact of disease involving chronic airflow limitation on health and well-being. The concurrent validity of the Chinese language version of the SGRQ in Taiwanese patients is supported by the findings of this investigation, with significant correlation between the SGRQ, the RAND 36-item Health Survey, and the Health Index. Two coefficients involving the SGRQ total score and two subscales of the RAND 36-item Health Survey (physical function and role limitation due to physical health) demonstrated medium to large effect size (r > 0.05) based on Cohen s criterion [13]. This means that the J Formos Med Assoc 2001 Vol 100 No 7 457

4 K.Y. Wang, C.H. Chiang, S.H. Maa, et al Table 2. Pearson s correlation coefficient between the St. George s Respiratory Questionnaire (SGRQ) and concurrent validity measures (n = 124) Concurrent validity measure Dimensions Symptoms Activity Impact SGRQ total score Health Index.264*.265*.349*.375* RAND 36-item Health Survey Physical function.244*.561*.393*.507* Role limitation due to physical health problems.323*.478*.517*.563* Energy/fatigue.328*.328*.470*.470* Emotional well-being *.305* Social function.389*.342*.480*.489* Bodily pain.323*.305*.356*.391* General health perception.326*.247*.426*.425* *p < 0.01; p < 0.05; p value for testing the Pearson s correlation coefficient. Table 3. Mean values of St. George s Respiratory Questionnaire (SGRQ) subscale and total scale score by asthma severity, emergency visit, and hospital admission N Symptoms Activity Impact SGRQ total Asthma severity Mild intermittent to mild persistent ± ± ± ± 15.2 Moderate persistent to severe persistent ± ± ± ± 20.3 p-value < < < < Emergency visit No ± ± ± ± 16.7 Yes ± ± ± ± 20.4 p-value < < < Hospital admission No ± ± ± ± 17.2 Yes ± ± ± ± 20.7 p-value < < p-value for testing the independent-samples t-test procedure. 458 degree of correlation between these coefficients is moderate to high. In the RAND 36-item Health Survey, role limitation due to physical health problems and emotional problems were more strongly associated with the impact score than with either the SGRQ symptom or activity (r > 0.5). A negative correlation was identified between the SGRQ (symptoms) and the RAND 36-item Health Survey (emotional well-being), although this was not statistically significant. The other two correlations with the SGRQ (activity and impact) and emotional well-being were lower than the remaining subscales. This might have been due to the fact that items specifically relating to anxiety and depression are not included in the SGRQ [1]. All coefficients were negative values indicating the relationships between the SGRQ and the RAND 36-item Health Survey or the Health Index were in the predicted direction with regard to scores. Evaluating differences across the spectrum of clinical asthma severity is difficult because the measurement of severity is still controversial [14]. However, a critical part of the validation of a health questionnaire is the demonstration that its scores are related to disease severity [15]. The SGRQ was able to distinguish patient groups based on asthma severity categorization. This finding is similar to the results of Jones et al [1]. They found that the SGRQ was suitable to quantify changes in the health of patients. Patients with severe asthma (lower FEV 1 %) had lower mean scores on the SGRQ total score and each of the three subscales. Several studies have reported that FEV 1 % had a significantly negative correlation with the SGRQ in asthma and COPD patients [4, 16, 17]. Patients with lower FEV 1 % are more likely to experience respiratory symptoms and bio-psychosocial function disturbances [1]. Wilson et al also found significantly worse SGRQ total scores in bronchiectasis patients who deteriorated compared to those who improved over a 6-month period in terms of wheezing and breathlessness (p < 0.01) [6]. The results of the present study are consistent with J Formos Med Assoc 2001 Vol 100 No 7

5 St. George's Respiratory Questionnaire those previous findings [1, 4, 6, 16, 17]. Patients who had emergency visits or hospital admissions had significantly higher SGRQ total scores and scores on each of the three subscales in the present study. Emergency visits and hospital admissions might be correlated with a worsening disease state [18]. This finding also confirms the discriminative property of the SGRQ. Although the SGRQ was developed to measure outcomes, it has also demonstrated good repeatability and responded quantitatively to changes in disease activity over an interval of a single year in two previous studies [3, 5]. The testing of the psychometric properties of this Chinese language version of the SGRQ instrument in Taiwanese asthma patients demonstrated that it can quantify the impact of diseases involving chronic airflow limitation on health and well-being, and distinguish patient s disease severity. To be fully confident of an instrument s validity in a new language or culture, a complete repetition of the validation process is required. Reliability estimates derived through this study demonstrated that the SGRQ is internally consistent in this population of Taiwanese. Each of the subscales and the entire scale of this study met Nunnally and Bernstein s criterion of 0.70 [19]. According to Nunnally and Bernstein, the target language version can be treated like a new instrument. Therefore, an α-coefficient of 0.70 may be considered adequate. These findings are consistent with the findings of Ferrer et al [4], Engstrom et al [5], and Harper et al [20]. Internal consistency of the SGRQ was 0.72 to 0.94, greater than 0.80, and 0.71 to 0.84, respectively. The high Cronbach s α-coefficient for the total scale suggests that a short form of the instrument could be created. In conclusion, the SGRQ is an instrument to evaluate the subjective perceived health status of asthma patients. The results of this study suggest that the Chinese language version of the SGRQ has internal consistency and validity with strong evidence of content, concurrent, and discriminating validity for Taiwanese asthma patients. Two future studies need to be conducted to fully demonstrate the psychometric properties of this instrument in the Taiwanese asthmatic population, a repetition of the validation process and the feasibility of an SGRQ short form. The reproducibility and sensitivity properties could be validated for the Chinese language version of the SGRQ with repeated evidence-based data. An SGRQ short form could replace a more complex instrument and provide a simple method for obtaining valid quality-of-life estimates for asthma patients. ACKNOWLEDGMENTS: The research was funded by grant no B from the National Science Council of Taiwan. References 1. Jones PW, Quirk FH, Baveystock CM, et al: A self-complete measure of health status for chronic airflow limitation: the St. George s Respiratory Questionnaire. Am Rev Respir Dis 1992;145: Quirk FH, Jones PW: Patients perception of distress due to symptoms and effects of asthma on daily living and an investigation of possible influential factors. Clin Sci 1990; 79: Jones PW, Quirk FH, Baveystock CM: The St George s Respiratory Questionnaire. Respir Med 1991;85:25S 31S. 4. Ferrer M, Alonso J, Prieto L, et al: Validity and reliability of the St. George s respiratory questionnaire after adaptation to a different language and culture: the Spanish example. Eur Respir J 1996;9: Engstrom C-P, Persson L-D, Larsson S, et al: Reliability and validity of a Swedish version of the St. George s Respiratory Questionnaire. Eur Respir J 1998;11: Wilson CB, Jones PW, O Leary CJ, et al: Validation of the St. George s Respiratory Questionnaire in bronchiectasis. Am J Respir Crit Care Med 1997;156: Quirk FH, Wilson BR, Jones PW: Influence of demographic and disease related factors on the degree of distress associated with symptoms and restrictions on daily living due to asthma in six countries. Eur Respir J 1991;4: Chapman D, Carter JF: Translation procedures for the cross-culture use of measurement. Educ Eval Policy Anal 1979;1: Jones EG, Kay M: Instrument in cross-culture research. Nurs Res 1992;41: National Asthma Education and Prevention Program (National Heart, Lung, and Blood Institute): Guidelines for the Diagnosis and Management of Asthma: Expert Panel Report 2 / National Institutes of Health, National Heart, Lung, and Blood Institute. Bethesda, MD: U.S. Department of Health and Human Services, Public Health Service, National Institutes of Health, National Heart, Lung, and Blood Insitute, Tarn YH: Establish the reliability and validity of the RAND 36-item Health Survey in Chinese. Thesis (DOH 85-TD-052). [In Chinese] 12. Wang KW, Chou WC, Kao CW: Factors influencing quality of life in patients with chronic obstructive pulmonary disease. J Med Sci 1998;18: Cohen J: Statistical Power Analysis for the Behavioral Sciences. 2nd ed. Hillsdale, NJ: Lawrence Erlbaum, 1988: Josephs LK, Gregg I, Mullee MA, et al: Nonspecific bronchial reactivity and its relationship to the clinical expression of asthma. Am Rev Respir Dis 1989; 140: Jones PW: Quality of life measurement in asthma. Eur Respir J 1995;5: Jones PW, Quirk FH, Baveystock CM: Why quality of life measures should be used in the treatment of patients with respiratory illness. Monaldi Arch Dis Chest 1994;49: J Formos Med Assoc 2001 Vol 100 No 7 459

6 K.Y. Wang, C.H. Chiang, S.H. Maa, et al 17. Renwick DS, Connolly MJ: Impact of obstructive airways disease on quality of life in older adults. Thorax 1996;51: Legorreta AP, Christian-Herman J, O Connor RD, et al: Compliance with national asthma management guidelines and specialty care: a health maintenance organization experience. Arch Intern Med 1998;158: Nunnally JC, Bernstein IH: Psychometric Theory. 3rd ed. New York: McGraw-Hill, 1994: Harper R, Brazier JE, Waterhouse JC, et al: Comparison of outcome measure for patients with chronic obstructive pulmonary disease (COPD) in an outpatient setting. Thorax 1997;52: J Formos Med Assoc 2001 Vol 100 No 7

A comparison of global questions versus health status questionnaires as measures of the severity and impact of asthma

Eur Respir J 1999; 1: 591±596 Printed in UK ± all rights reserved Copyright #ERS Journals Ltd 1999 European Respiratory Journal ISSN 93-1936 A comparison of global questions versus health status questionnaires