ORIGINAL ARTICLE Evaluation of the chronic obstructive pulmonary disease assessment test for measurement of health-related quality of life in patients with interstitial lung disease KAZUMA NAGATA, KEISUKE TOMII, KOJIRO OTSUKA, RYO TACHIKAWA, KYOKO OTSUKA, JUNPEI TAKESHITA, KOSUKE TANAKA, TAKESHI MATSUMOTO AND KAZUYA MONDEN Department of Respiratory Medicine, Kobe City Medical Center General Hospital, Kobe, Japan ABSTRACT Background and objective: A well-validated instru- ment that is simple to use is needed to assess health- related quality of life in patients with interstitial lung disease (ILD). The COPD assessment test (CAT) is a recently introduced, short and simple questionnaire for COPD patients, which shows good and valid mea- surement properties. This study was conducted to evaluate the validity of the CAT in patients with ILD. Methods: Patients with ILD (n = 55) completed the CAT and the St. George’s Respiratory Questionnaire (SGRQ). These patients also completed the Medical Research Council (MRC) dyspnoea scale, the Leicester Cough Questionnaire (LCQ), and the hospital anxiety and depression scale; performed 6-min walk tests and pulmonary function tests; and provided samples for arterial blood gas analysis. Results: There was a very strong correlation between the CAT score and the SGRQ total score (r = 0.93, P < 0.0001). The CAT score was also signifi- cantly correlated with the SGRQ symptoms score (r = 0.74, P < 0.0001), the SGRQ activity score (r = 0.87, P < 0.0001) and the SGRQ impact score (r = 0.89, P < 0.0001). Stepwise multiple regression analysis demonstrated that the MRC and LCQ scores contrib- uted most to both the CAT score and the SGRQ total score. Conclusions: The CAT is a short and simple question- naire that shows good and valid measurement proper- ties for assessing the health status of patients with ILD. Key words: chronic obstructive pulmonary disease assessment test, dyspnoea, health-related quality of life, interstitial lung disease, St. George’s Respiratory Questionnaire. INTRODUCTION Interstitial lung disease (ILD) is a chronic, progressive disease that is associated with increased morbidity and mortality. 1 ILD is associated with many symp- toms, including shortness of breath and cough, and as the disease progresses, these symptoms impair the patient’s quality of life. 2,3 In the management of this disease, clinicians tend to focus on physiological parameters, which are of limited interest to patients; they are most interested and familiar with their functional capacity and well- being. It is crucial to obtain complete information on the impact of ILD on the health status of patients, including daily symptoms, limitation of activities and other manifestations of the disease. This information is often referred to as the health-related quality of life (HRQL), which assesses a patient’s satisfaction across a wide range of life domains. There are some generic and condition-specific instruments that measure HRQL. There have been several reports relating to HRQL in patients with ILD. 3–9 The St. George’s Respiratory Questionnaire (SGRQ) was originally designed and validated for use in patients with chronic obstructive pulmonary disease (COPD), 10 and it has also been validated for use in patients with ILD. 6,11,12 Furthermore, Yorke et al. developed and validated an idiopathic pulmonary fibrosis (IPF)-specific version of the SGRQ. 7 These instruments make it easy to gather informa- tion about the impact of the disease on patients. However, they are lengthy and involve scoring algo- rithms that are too complex for routine use in clinical Correspondence: Kazuma Nagata, Department of Respiratory Medicine, Kobe City Medical Center General Hospital, 4-6 Minatojima-nakamachi, Chuo-ku, Kobe, 650-0046, Japan. Email: kazuma_n1101@yahoo.co.jp Received 20 September 2011; invited to revise 16 October 2011; revised 20 October 2011; accepted 27 October 2011 (Asso- ciate Editor: David Hui). SUMMARY AT A GLANCE In this study, the validity of the COPD assessment test (CAT) was evaluated in patients with intersti- tial lung disease. The CAT score was strongly cor- related with the St. George’s Respiratory Questionnaire score and was influenced by the same variables. © 2012 The Authors Respirology © 2012 Asian Pacific Society of Respirology Respirology (2012) 17, 506–512 doi: 10.1111/j.1440-1843.2012.02131.x