Portuguese-language version of the Chronic Respiratory Questionnaire: a validity and reproducibility study

Abstracts

OBJETIVO: Verificar a validade e a reprodutibilidade de uma versão em português do Chronic Respiratory Questionnaire (CRQ) em pacientes com DPOC. MÉTODOS: A versão em português do CRQ (fornecida pela Universidade de McMaster, detentora dos direitos do questionário) foi aplicada a 50 pacientes portadores de DPOC (32 homens; 70 ± 8 anos; VEF1 = 47 ± 18% predito) em dois momentos, com intervalo de uma semana. O CRQ tem quatro domínios (dispneia, fadiga, função emocional e autocontrole) e foi aplicado em formato de entrevista. O Saint George's Respiratory Questionnaire (SGRQ), já validado em português, foi utilizado como o critério de validação. A espirometria e o teste da caminhada de seis minutos (TC6) foram realizados para a análise das correlações com os valores do CRQ. RESULTADOS: Não foram observadas diferenças significativas entre a aplicação e a reaplicação do CRQ (p > 0.05 para todos os domínios). O coeficiente de correlação intraclasse entre a aplicação e a reaplicação foi de 0,98; 0,97; 0,98 e 0,95 para os domínios dispneia, fadiga, função emocional e autocontrole, respectivamente. O coeficiente alfa de Cronbach foi 0,91. Os domínios do CRQ se correlacionaram significativamente com os domínios do SGRQ (-0.30 < r < -0.67; p < 0,05). Não houve correlação entre as variáveis espirométricas e os domínios do CRQ e nem entre esses domínios e o TC6, exceto para o domínio fadiga (r = 0,30; p = 0,04). CONCLUSÕES: A versão em português do CRQ demonstrou ser reprodutível e válida em pacientes brasileiros portadores de DPOC.

Qualidade de vida; Doença pulmonar obstrutiva crônica; Questionários

ORIGINAL ARTICLE

Portuguese-language version of the Chronic Respiratory Questionnaire: a validity and reproducibility study^*

Graciane Laender Moreira^I; Fábio Pitta^II; Dionei Ramos^III; Cinthia Sousa Carvalho Nascimento^IV; Danielle Barzon^IV; Demétria Kovelis^V; Ana Lúcia Colange^IV; Antonio Fernando Brunetto^III; Ercy Mara Cipulo Ramos^III

^IMasters Student in Physical Therapy. Faculdade de Ciências e Tecnologia/Universidade Estadual Paulista - FCT/UNESP, School of Science and Technology/São Paulo State University - Presidente Prudente, Brazil

^IIProfessor. Faculdade de Ciências e Tecnologia/Universidade Estadual Paulista - FCT/UNESP, School of Science and Technology/São Paulo State University - Presidente Prudente, Brazil

^IIIProfessor. Faculdade de Ciências e Tecnologia/Universidade Estadual Paulista - FCT/UNESP, School of Science and Technology/São Paulo State University - Presidente Prudente, Brazil

^IVPhysical Therapy Student. Universidade Estadual de Londrina - UEL, Londrina State University - Londrina, Brazil

^VPhysical Therapist. Laboratório de Pesquisa em Fisioterapia Pulmonar - LFIP, Respiratory Therapy Research Laboratory - Department of Physical Therapy, Universidade Estadual de Londrina - UEL, Londrina State University - Londrina, Brazil.

Correspondence to

ABSTRACT

OBJECTIVE: To determine the validity and reproducibility of a Portuguese-language version of the Chronic Respiratory Questionnaire (CRQ) in patients with COPD.

METHODS: A Portuguese-language version of the CRQ (provided by McMaster University, the holder of the questionnaire copyright) was applied to 50 patients with COPD (70 ± 8 years of age; 32 males; FEV₁ = 47 ± 18% of predicted) on two occasions, one week apart. The CRQ has four domains (dyspnea, fatigue, emotional function, and mastery) and was applied as an interviewer-administered instrument. The Saint George's Respiratory Questionnaire (SGRQ), already validated for use in Brazil, was used as the criterion for validation. Spirometry and the six-minute walk test (6MWT) were performed to analyze the correlations with the CRQ scores.

RESULTS: There were no significant CRQ test-retest differences (p > 0.05 for all domains). The test-retest intraclass correlation coefficient was 0.98, 0.97, 0.98 and 0.95 for the dyspnea, fatigue, emotional function and mastery domains, respectively. The Cronbach's alpha coefficient was 0.91. The CRQ domains correlated significantly with the SGRQ domains (-0.30 < r < -0.67; p < 0.05). There were no significant correlations between spirometric variables and the CRQ domains or between the CRQ domains and the 6MWT, with the exception of the fatigue domain (r = 0.30; p = 0.04).

CONCLUSIONS: The Portuguese-language version of the CRQ proved to be reproducible and valid for use in Brazilian patients with COPD.

Keywords: Quality of life; Pulmonary disease, chronic obstructive; Questionnaires.

Introduction

The respiratory disease COPD is characterized by chronic airflow limitation that is usually progressive and not fully reversible. It presents some significant extrapulmonary effects⁽¹⁾ that can decrease functional capacity and impair social interaction in such patients,⁽²⁾ as well as negatively affecting their well-being and quality of life.⁽³⁾

The use of subjective measures (such as questionnaires) in order to assess the quality of life of COPD patients in scientific research has been widely accepted.⁽⁴⁾ The creation of reliable and valid questionnaires has contributed to a substantial increase in their use.⁽⁵⁾

Two of the three principal models of respiratory disease-specific questionnaires currently in use are the Saint George's Respiratory Questionnaire (SGRQ)⁽⁶⁾ and the Airways Questionnaire 20 (AQ20),⁽⁷⁾ both of which have already been validated for use in Brazil.^(8-10) The third is the Chronic Respiratory Questionnaire (CRQ).⁽¹¹⁾

The CRQ has been widely used in the analysis of the health status of patients with COPD. The CRQ has been translated and validated for use in the Netherlands,⁽¹²⁾ in Spain⁽¹³⁾ and in three German-speaking countries (Switzerland, Germany and Austria).⁽¹⁴⁾ It has proven to be useful in a variety of interventions in COPD, including pharmacological interventions⁽¹⁵⁾ and rehabilitation.^(14,16) In addition, among the instruments that specifically assess the quality of life of patients with COPD, the CRQ has proven to be superior to the SGRQ because it is more responsive to interventions, such as pulmonary rehabilitation programs.^(17,18) Although the CRQ is widely used to assess the quality of life of patients with COPD,⁽¹⁹⁾ no Portuguese-language version of this questionnaire has been validated for use in Brazil.

In order to measure the health status of patients whose language and culture are different from those for which the questionnaire was developed, it is recommended that the instrument be validated.^(20,21) Therefore, it is necessary to adapt the questionnaire to the cultural context of the population studied, since the perception of time, the meaning attributed to the symptoms and the course of a given disease can vary from culture to culture.⁽²²⁾ In addition, if studies using translated questionnaires are to achieve international acceptance, they must employ questionnaires validated for use in the target language.⁽²³⁾

Therefore, the objective of the present study was to determine whether the Portuguese-language version of the CRQ, which is a respiratory disease-specific quality-of-life questionnaire, is a valid and reproducible instrument for measuring the quality of life of Brazilian patients with COPD.

Methods

Fifty individuals with COPD were included in the present study. Of those, 28 were recruited from the Pulmonary Rehabilitation Program of the Hospital Universitário Regional Norte do Paraná, Universidade Estadual de Londrina (HURNPR/UEL, Northern Paraná University Hospital/Londrina State University), located in the state of Paraná, Brazil, and 22 were recruited from the Pulmonary Rehabilitation Program of the Center for Physical Therapy and Rehabilitation Studies and Treatment of the São Paulo State University, Presidente Prudente Campus, located in the state of São Paulo, Brazil.

All patients had been clinically diagnosed with COPD according to the criteria established by the Global Initiative for Chronic Obstructive Lung Disease (GOLD).⁽¹⁾ In addition, patients should be clinically stable (free of exacerbations or infections in the last 3 months) in order to be included in the study. The exclusion criteria were as follows: presenting other diseases (pulmonary or otherwise) considered severe or disabling; failing to appear for the scheduled appointments; presenting acute exacerbations during the evaluation period; being unable to understand the questionnaires or other tests; and being uncooperative.

The study was approved by the HURNPR/UEL Research Ethics Committee (ruling no. 064/06). After the selected patients had been advised of the study procedures and objectives, all gave written informed consent.

In order to determine the reproducibility of the CRQ, a Portuguese-language version of this questionnaire was administered to all participating patients. The questionnaire was applied on two occasions, one week apart, and was administered by the same interviewer on both occasions. The concurrent and criterion validity of the CRQ were evaluated based on the correlation of the CRQ scores with the SGRQ scores-the SGRQ having already been validated for use in Brazil⁽⁹⁾-as well as on the correlation of the CRQ scores with the results of spirometry and the six-minute walk test (6MWT).

The CRQ, published by Guyatt et al.⁽¹¹⁾ in 1987, was the first instrument developed to measure the quality of life of patients with COPD and has been widely used in international studies.⁽¹⁹⁾ This questionnaire can be administered by an interviewer (original version),⁽¹¹⁾ or it can be self-administered.⁽²⁴⁾ It consists of 20 questions grouped into four domains: dyspnea (5 questions); fatigue (4 questions); emotional function (7 questions); and mastery (4 questions). The dyspnea domain is individualized, that is, each patient selects, in a list of 26 items, the activities that caused dyspnea in the last two weeks. In addition, the patient can report activities that are do not appear on the list. Subsequently, from among the activities reported and selected, individuals choose five activities that they consider the most important and, using a seven-point scale, score their dyspnea for each of those activities. This scale ranges from 1 (maximum impairment) to 7 (no impairment). For the other domains (fatigue, emotional function and mastery), the questions are standardized and the patient responds to each question using the seven-point scale. A higher score translates to better quality of life. The results are expressed as mean scores, by domain. The minimum clinically important difference, which refers to the minimum amount of change that is significant for patients in their everyday life (improved or worsened quality of life) is 0.5 points.

In the present study, back-translation of the CRQ was not necessary, since McMaster University (Hamilton, Ontario, Canada), which is the holder of the copyright of the original English-language questionnaire,⁽¹¹⁾ officially granted us the rights to use a Portuguese-language version of the CRQ that was developed at McMaster University and had never been validated for use in Brazil or in any other Portuguese-speaking country. After this version had been read and carefully analyzed, it was applied, as an interviewer-administered instrument, to a small sample of patients with COPD in order to identify possible problems and difficulties related to the questions. Since there were no terms or situations that could not be applied to Brazilians, it was not necessary to make any changes to the questions in order to achieve cross-cultural equivalence. This made it possible to administer the questionnaire directly and immediately. Those interested in using the CRQ should request a copy of the questionnaire directly from McMaster University (contact: Ms. Peggy Austin: [e-mail]).

The SGRQ was developed by Jones et al.⁽⁶⁾ to assess the quality of life of patients with COPD and was first validated for use in Brazil by Sousa et al.⁽⁸⁾ This questionnaire addresses aspects regarding three domains: symptoms (24 items); activity (16 items); and (psychosocial) impact (36 items). Each domain has a maximum possible score (symptoms, 662.5 points; activity, 1,209.1 points; and impact, 2,117.8 points). The scores obtained for all of the questions in a given domain are summed, and the total is expressed as a percentage of the maximum for that domain (0-10%). In addition to the scores for each domain, a total score is calculated based on the results obtained for the three domains (0-3,989.4 points). A higher score translates to poorer quality of life.

Recently, in view of the difficulty of patients in understanding the double-negative sentences of the original version, a new version of this questionnaire was validated for use in Brazil by Camelier et al.⁽⁹⁾ In this new version, the options "yes" and "no" have been replaced with "agree" and "disagree", in order to facilitate comprehension. Furthermore, the assessment interval was reduced from 12 months to 3 months. This new version, devised by Camelier et al.,⁽⁹⁾ was used in the present study, and was administered by the same interviewer.

In addition to being interviewed in order to complete the questionnaires, the patients underwent spirometry, which was performed in accordance with the norms of the Pulmonary Function Test Guidelines established by the Brazilian Thoracic Association.⁽²⁵⁾ The patients enrolled in the HURNPR/UEL Rehabilitation Program were evaluated using a Pony Graphics spirometer (Cosmed, Rome, Italy), whereas those recruited from the School of Science and Technology/São Paulo State University were evaluated using a Spirobank spirometer (MIR, Rome, Italy). The reference values adopted were those established by Pereira et al.⁽²⁶⁾

The 6MWT was performed according to international standards,⁽²⁷⁾ in a 30-m corridor. Two tests were performed at least 30 min apart, and the highest value was used in the analysis. The reference values used were those established by Troosters et al.⁽²⁸⁾

The statistical analysis was performed using the program GraphPad Prism 3.0 (GraphPad Software Inc., San Diego, CA, USA). Nonparametric statistical analysis was used because the data were ordinal. The CRQ test-retest reproducibility (test days designated day 1 and day 2, respectively) was determined using the intraclass correlation coefficient (ICC), as well as the Wilcoxon test. The concordance between day 1 and day 2 was visually assessed using Bland & Altman plots. The internal consistency of the questionnaire was assessed using Cronbach's alpha coefficient. The validity of the CRQ in relation to the SGRQ, as well as the correlation of the CRQ with spirometric variables and with the six-minute walk distance, was determined using Spearman's correlation coefficient. The level of statistical significance was set at 5% (p < 0.05).

Results

Most of the 50 patients included in the study were classified as having GOLD stage II or III COPD (Table 1). There was a predominance of males (64%) and literate individuals (82%). None of the patients used home oxygen therapy, and 46 patients (92%) regularly used physician-prescribed bronchodilators. The clinical characteristics of the patients can be seen in Table 1. None of the patients were excluded from the study.

Regarding the CRQ test time, there was a statistically significant difference (p < 0.0001) between day 1 and day 2. The mean test time on days 1 and 2 was 20 ± 6 min and 17 ± 5 min, respectively.

In the comparison between day 1 and day 2, there were no significant differences in any of the domains of the questionnaire, as can be seen in Figure 1. For the four domains, the ICC between day 1 and day 2 was as follows: dyspnea, 0.98; fatigue, 0.97; emotional function, 0.98; and mastery, 0.95. Bland & Altman plots (Figure 2) showed good test-retest concordance for the CRQ. The Cronbach's alpha coefficient was 0.91 overall, whereas it was 0.86, 0.78, 0.81 and 0.70, respectively, for the dyspnea, fatigue, emotional function and mastery domains.

There were significant correlations between the CRQ domains and the SGRQ domains (-0.30 < r < -0.67; p < 0.05), with the exception of the CRQ emotional function domain in relation to the SGRQ symptoms domain (r = -0.14; p = 0.33), as can be seen in Table 2. There were no significant correlations between spirometric variables and the CRQ domains or between the CRQ domains and the 6MWT, with the exception of the fatigue domain (r = 0.30; p = 0.04).

Discussion

Since most quality-of-life questionnaires have been developed in English-speaking countries, a validation process is required before these questionnaires are used in other countries.^(20,21) Therefore, for the questionnaire to be considered appropriate for scientific or clinical use, it is necessary to evaluate its reproducibility and its correlation with other instruments already validated with the same objective or, in certain cases, with traditionally used clinical parameters.⁽²⁹⁾ The results of the present study show that the Portuguese-language version of the CRQ is reproducible and valid for use in assessing the quality of life of Brazilian patients with COPD.

The absence of statistically significant test-retest differences, together with the high ICC values for the different CRQ domains, demonstrates the reproducibility of this instrument. For all of the CRQ domains, the ICC was above 0.95, the values being greater than those observed in studies involving validation of the CRQ for use in other countries.^(11-13) The reproducibility of the questionnaire was also visually assessed using Bland & Altman plots (Figure 2), which demonstrated good concordance between day 1 and day 2.

Regarding the CRQ test time, there was a statistically significant difference between day 1 and day 2, the test time being shorter on day 2. We believe that this difference might be due not only to the fact that the patients had better comprehension of the sentences but also to the fact that, in the dyspnea domain, the number of activities reported by the patients on day 1 was different from that reported on day 2. For most patients, the number of activities that caused dyspnea reported on day 1 was greater than that reported on day 2. Since the patients had more activities from which they should choose only the five most important, more time was required. Despite this difference, the CRQ test time ranged from 12 to 26 min, which is in agreement with the findings of previous studies.^(11,13,14)

In the present study, the validity of the Portuguese-language version of the CRQ for use in Brazil was shown by the significant correlation of its various domain scores with the domain scores and total score of the SGRQ, which is a traditional questionnaire and has already been validated for use in Brazil.⁽⁹⁾ However, there was no significant correlation between the CRQ emotional function domain and the SGRQ symptoms domain. This might have occurred because the questions in the CRQ emotional function domain address aspects that are not directly associated with the aspects addressed by the questions in the SGRQ symptoms domain. Of the 7 questions in the emotional function domain, only 2 are related to emotional changes caused by the cough and dyspnea presented by the patient. Those 2 questions address the frequency with which patients have felt embarrassed because of their cough or labored breathing (question 9) and the frequency with which they have felt restless, tense or nervous (question 20) in the last two weeks.

In addition, none of the CRQ domains correlated with any of the spirometric variables. This finding is consistent with those of a previous study,⁽³⁰⁾ which demonstrated that the measurement of quality-of-life in patients with COPD might not be directly related to traditional physiological measures, since it reflects patient experiences and perspectives, regardless of the degree of respiratory muscle dysfunction. In the present study, this is corroborated by the limited correlation between the CRQ domains and the 6MWT. Another possible explanation for this limited correlation between the CRQ domains and the 6MWT is the fact that the patients in our sample (Table 1) presented relatively preserved exercise capacity in relation to that of patients participating in previous studies.^(11,13,14)

When comparing the scores of each CRQ domain obtained for the Brazilian patients with those obtained for patients from other countries in which the CRQ was validated,^(13,14) we observed that the scores found for the fatigue, emotional function and mastery domains in the present study (4.5 ± 1.2; 4.8 ± 1.0; and 5.1 ± 1.3, respectively) were similar to those found for the Spanish-language version (4.47 ± 1.20; 4.80 ± 1.26; and 5.0 ± 1.5, respectively) and those found for the German-language version, with the exception of the mastery domain (4.2 ± 1.2, 4.4 ± 1.0 and 4.4 ± 1.2, respectively). However, for the dyspnea domain, the score obtained for the Brazilian population was considerably higher (4.6 ± 1.3) than that obtained for the Spanish population (3.15 ± 1.00) and for the German-speaking population (3.17 ± 0.66), indicating a better quality of life for this domain. Although no formal statistical analysis has been performed to confirm such inferences, the > 0.5 point difference in each domain (the minimum clinically important difference for improved or worsened quality of life)⁽¹¹⁾ was considered the basis for drawing the inference that the values for the groups of Brazilian patients, German-speaking patients and Spanish patients were similar (with the exception of the CRQ dyspnea domain).

The difference found among the populations in terms of the dyspnea domain score might indicate culturally specific aspects related to the perception of dyspnea. The discrepancy in the scores of this domain might also be related to the relatively preserved exercise capacity of the Brazilian population (6MWT: 445 ± 64 m) in relation to that of the Spanish population (306 ± 56 m) and that of the German-speaking population (359 ± 111 m), as well as to other differences among the populations studied. Further studies addressing this issue might help clarify this discrepancy.

The lack of data regarding the responsiveness of the Portuguese-language version of the CRQ to interventions, such as pulmonary rehabilitation, can be considered a limitation of the present study. However, as previously mentioned, the CRQ (in its original version) is considered the most responsive of the instruments currently available.^(17,18) Therefore, since the Portuguese-language version proved to be equally valid and reproducible in relation to the original version, there is no reason to believe that the former would fail to present similar responsiveness, although this has yet to be objectively investigated.

In summary, the Portuguese-language version of the CRQ proved to be reproducible and valid for use in Brazilian patients with COPD. It is an important instrument for use by clinicians and researchers, increasing the options available to assess the quality of life of patients with COPD.

Acknowledgments

The authors would like to thank the physical therapist Nicoli Oldemberg Segretti for her contribution to the development of the present study.

References

• 1. Rabe KF, Hurd S, Anzueto A, Barnes PJ, Buist SA, Calverley P, et al. Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease: GOLD executive summary. Am J Respir Crit Care Med. 2007;176(6):532-55.
• 2. Haave E, Hyland ME, Skumlien S. The relation between measures of health status and quality of life in COPD. Chron Respir Dis. 2006;3(4):195-9.
• 3. McCathie HC, Spence SH, Tate RL. Adjustment to chronic obstructive pulmonary disease: the importance of psychological factors. Eur Respir J. 2002;19(1):47-53.
• 4. Tsai CL, Hodder RV, Page JH, Cydulka RK, Rowe BH, Camargo CA Jr. The short-form chronic respiratory disease questionnaire was a valid, reliable, and responsive quality-of-life instrument in acute exacerbations of chronic obstructive pulmonary disease. J Clin Epidemiol. 2008;61(5):489-97.
• 5. Curtis JR, Patrick DL. The assessment of health status among patients with COPD. Eur Respir J Suppl. 2003;41:36s-45s.
• 6. Jones PW, Quirk FH, Baveystock CM. The St George's Respiratory Questionnaire. Respir Med. 1991;85 Suppl B:25-31; discussion 33-7.
• 7. Quirk FH, Jones PW. Repeatability of two new short airways questionnaires. Proceedings of the British Thoracic Society; 1994 Jun 29 - Jul 1; Manchester, UK. Thorax. 1994;49(10):1075.
• 8. Sousa TC, Jardim JR, Jones P. Validação do Questionário do Hospital Saint George na Doença Respiratória (SGRQ) em pacientes portadores de doença pulmonar obstrutiva crônica no Brasil. J Pneumol. 2000;26(3):119-28.
• 9. Camelier A, Rosa FW, Salmi C, Nascimento AO, Cardoso F, Jardim JR. Using the Saint George's Respiratory Questionnaire to evaluate quality of life in patients with chronic obstructive pulmonary disease: validating a new version for use in Brazil. J Bras Pneumol. 2006;32(2):114-22.
• 10. Camelier A, Rosa F, Jones P, Jardim JR. Validação do questionário de vias aéreas 20 ("Airways questionnaire" - AQ20) em pacientes portadores de doença pulmonar obstrutiva crônica (DPOC) no Brasil. J Pneumol. 2003;29(1):28-35.
• 11. Guyatt GH, Berman LB, Townsend M, Pugsley SO, Chambers LW. A measure of quality of life for clinical trials in chronic lung disease. Thorax. 1987;42(10):773-8.
• 12. Wijkstra PJ, TenVergert EM, Van Altena R, Otten V, Postma DS, Kraan J, et al. Reliability and validity of the chronic respiratory questionnaire (CRQ). Thorax. 1994;49(5):465-7.
• 13. Güell R, Casan P, Sangenís M, Morante F, Belda J, Guyatt GH. Quality of life in patients with chronic respiratory disease: the Spanish version of the Chronic Respiratory Questionnaire (CRQ). Eur Respir J. 1998;11(1):55-60.
• 14. Puhan MA, Behnke M, Laschke M, Lichtenschopf A, Brändli O, Guyatt GH, et al. Self-administration and standardisation of the chronic respiratory questionnaire: a randomised trial in three German-speaking countries. Respir Med. 2004;98(4):342-50.
• 15. Jaeschke R, Guyatt GH, Willan A, Cook D, Harper S, Morris J, et al. Effect of increasing doses of beta agonists on spirometric parameters, exercise capacity, and quality of life in patients with chronic airflow limitation. Thorax. 1994;49(5):479-84.
• 16. Wijkstra PJ, Van Altena R, Kraan J, Otten V, Postma DS, Koëter GH. Quality of life in patients with chronic obstructive pulmonary disease improves after rehabilitation at home. Eur Respir J. 1994;7(2):269-73.
• 17. Singh SJ, Sodergren SC, Hyland ME, Williams J, Morgan MD. A comparison of three disease-specific and two generic health-status measures to evaluate the outcome of pulmonary rehabilitation in COPD. Respir Med. 2001;95(1):71-7.
• 18. Puhan MA, Guyatt GH, Goldstein R, Mador J, McKim D, Stahl E, et al. Relative responsiveness of the Chronic Respiratory Questionnaire, St. Georges Respiratory Questionnaire and four other health-related quality of life instruments for patients with chronic lung disease. Respir Med. 2007;101(2):308-16.
• 19. Lacasse Y, Wong E, Guyatt GH, King D, Cook DJ, Goldstein RS. Meta-analysis of respiratory rehabilitation in chronic obstructive pulmonary disease. Lancet. 1996;348(9035):1115-9.
• 20. Guillemin F, Bombardier C, Beaton D. Cross-cultural adaptation of health-related quality of life measures: literature review and proposed guidelines. J Clin Epidemiol. 1993;46(12):1417-32.
• 21. Guillemin F. Cross-cultural adaptation and validation of health status measures. Scand J Rheumatol. 1995;24(2):61-3.
• 22. Ramos-Cerqueira AT, Crepaldi AL. Qualidade de vida em doenças pulmonares crônicas: aspectos conceituais e metodológicos. J Pneumol. 2000;26(4):207-13.
• 23. Ferreira CA, Cukier A. Evaluating COPD from the perspective of the patient. J Bras Pneumol. 2006;32(2):VII-VIII.
• 24. Williams JE, Singh SJ, Sewell L, Guyatt GH, Morgan MD. Development of a self-reported Chronic Respiratory Questionnaire (CRQ-SR). Thorax. 2001;56(12):954-9.
• 25. Sociedade Brasileira de Pneumologia. Diretrizes para testes de função pulmonar. J Bras Pneumol. 2002;28(Suppl 3):1-238.
• 26. Pereira CA, Barreto SP, Simoes JG, Pereira FW, Gerstler JG, Nakatami J. Valores de referência para a espirometria em uma amostra da população brasileira adulta. J Pneumol. 1992;18(1):10-22.
• 27. Brooks D, Solway S, Gibbons WJ. ATS statement on six-minute walk test. Am J Respir Crit Care Med. 2003;167(9):1287.
• 28. Troosters T, Gosselink R, Decramer M. Six minute walking distance in healthy elderly subjects. Eur Respir J. 1999;14(2):270-4.
• 29. Streiner DL, Norman GR. Health measurement scales: a practical guide to their development and use. Oxford: Oxford University Press; 2003
• 30. Tashkin DP. The role of patient-centered outcomes in the course of chronic obstructive pulmonary disease: how long-term studies contribute to our understanding. Am J Med. 2006;119(10 Suppl 1):63-72.

*

Trabalho realizado na Faculdade de Ciências e Tecnologia/Universidade Estadual Paulista - FCT/UNESP - Presidente Prudente (SP) e na Universidade Estadual de Londrina - UEL - Londrina (PR) Brasil.

Publication Dates

• Publication in this collection
  08 Sept 2009
• Date of issue
  Aug 2009

History

• Accepted
  16 Apr 2009
• Received
  16 Feb 2009