Abstract
Aims: The CAT is a short, simple eight-item questionnaire for assessing and monitoring COPD. It is not known how reliable the CAT scores are for COPD patients who are frequently exacerbated. The effectiveness of the CAT for assessing COPD severity and exacerbation rates was evaluated. Methods: This study enrolled 165 stable COPD patients who completed the CAT between April 2011 and February 2012. Results: Patients had a mean forced expiratory volume in one second (FEV1) equal to 43.7% of the predicted value and a mean CAT score of 21.2 (± 7.56) units. There was a good association between the FEV1 (percentage of predicted value) and CAT scores (p < 0.0001). Frequent exacerbators had significantly higher CAT scores than infrequent exacerbators (24.8 ± 6.7 versus 17.5 ± 6.5, p < 0.0001). Also, as the frequency of the COPD exacerbations increased, CAT scores (p < 0.0001) significantly increased. There was a significant association between the frequency of hospitalization and the CAT scores (p = 0.001). Conclusions: We observed a good relation between the CAT, FEV 1, and disease severity in patients with COPD. We found that the baseline CAT scores are elevated in frequent exacerbators.
Introduction
The CAT is a recently introduced, patient-completed quality of life instrument that contains eight questions which cover the impact of COPD symptoms (Citation1). The scoring scale ranges from 0–40 points and indicates the impact of the disease. Scores between 0–10, 11–20, 21–30 and 31–40 represent mild, moderate, severe or very severe clinical impact, respectively. An advantage of the CAT is the results are immediately available without the need for complex calculation. Initial studies have shown that the CAT correlates closely with health-related quality of life as measured by the St. George's Respiratory Questionnaire (SGRQ) in patients with COPD (Citation1).
Quality of life is impaired by COPD exacerbations, which are characterized by worsening respiratory symptoms (Citation2). Although we know that exacerbations are key events in COPD, our knowledge of their frequency, determinants, and effects is incomplete. CAT scores increase with the severity of the disease (Citation1, 2), but we know little about the relationship between the exacerbation rates and CAT scores. Therefore, we wanted to discover the correlation between COPD exacerbations, COPD severity and CAT scores.
Subjects and Methods
This was a prospective observational study carried out from April 2011 to February 2012. One hundred and sixty-five patients with COPD in stable condition from one government hospital and two chest diseases education and training hospitals were assessed by a face-to-face interview using the Turkish version of the CAT (www.catestonline.org/images/pdfs/TurkeyCATest.pdf). It is demonstrated that The Turkish version of COPD Assessment Test is reliable and valid (Citation3). The patients also underwent a pulmonary function test on the same day. A chest X-ray was performed on all patients to exclude other problems. The patients’ self-reported respiratory symptoms, medications, smoking history, occupational exposure, exacerbation rates over the past 12 months, and coexisting medical conditions were documented at the beginning of the study. Comorbid diagnoses were established using the clinical history and physical examination findings during the visit and were supported by a review of the available medical records.
Written informed consent was obtained from all patients, and the study was approved by the relevant ethics and review boards. The recruitment criteria included a minimum age of 40 years old, a history of 10 or more pack-years of smoking or a history of biomass exposure, a forced expiratory volume in 1 second (FEV1) of less than 80% of the predicted value after bronchodilator use and a ratio of FEV1 to forced vital capacity (FVC) of 0.7 or less after bronchodilator use (Citation4). The condition of the patients was graded according to the stages of disease defined by the Global Initiative for Chronic Obstructive Lung Disease (GOLD) (Citation5). Patients not meeting the inclusion criteria or with a primary diagnosis of asthma, other active chronic pulmonary disease, or other severe, uncontrolled comorbidities were excluded.
Currently, there is no universally agreed upon method to identify exacerbations. ATS and ERS define a COPD exacerbation as “an event in the natural course of the disease characterized by a change in the patient's baseline dispnea, cough and/or sputum from day to day variability sufficient to warrant a change in management” (Citation6). This definition is comprehensive and explains the fact that exacerbations have varied effects and symptoms. Exacerbation definitions fall into three groups: event-based, symptom-based and a combination of two. We used a symptom-based definition developed by Anthonisen et al. (Citation7). Anthonisen et al. defined exacerbation as increase in sputum purulence, increase in sputum volume and worsening of dyspnea. We defined an exacerbation as the symptom-base definition of increase in sputum purulence, increase in sputum volume and worsening of dyspnea and this definition should involve an unexpected doctor visit or an emergency department application which causes a change in disease management.
Patients who averaged ≥2 COPD exacerbations a year were classified as frequent exacerbators, whereas those who had ≤1 COPD exacerbations per year were defined as infrequent exacerbators.
All the durable variables and compared subgroups were analyzed and tested for the normality of the data. The different averages were compared using Student's t-test for those that were parametric or the Mann-Whitney U-test for those that were non-parametric. ROC analysis was used to assess the ability of CAT to predict frequently exacerbator subgroup. A correlation coefficient was estimated for determining the relationship between the numeric variables. A 5% significance level was used to determine the achievement of statistical significance. Ninety-five percent confidence intervals (CIs) were calculated where appropriate. All tests were two-tailed, and statistical processing was carried out using the Statistical Package for the Social Sciences (SPSS) version 12 for Windows (SPSS Inc., Chicago, Illinois, USA).
Results
The study included 165 patients (mean age 65.01 ± 9.9 years; 149 male (90.3%)). reveals the baseline characteristics of the patients who participated in the study. Thirty-one (18%) patients never graduated from school, 103 (62%) graduated from elementary school, and 31 (18%) graduated from high school or university. Seventy-nine (47%) patients had an accompanying disease (diabetes mellitus (n = 9), hyperlipidemia (n = 17), cardiovascular disease (n = 51), gastrointestinal diseases (n = 7), sleep disorders (n = 12), depression (n = 7), chronic pain (n = 6), and lung cancer (n = 4)). The mean FEV1 was 43.7% of the predicted value.
Table 1. Demographic and clinical characteristics of patients
The mean CAT score completed by the patients was 21.2 (±7.5) (). Frequent exacerbators (n = 84) had a mean CAT score of 24.8 (± 6.7) compared to infrequent exacerbators (n = 81) whose mean CAT score was 17.5 (±6.5). Thus, there was an average difference of 7.3 points in the CAT scores between the frequent and infrequent exacerbators ( p < 0.0001) ().
Figure 1. The relationship between COPD exacerbation frequency and total CAT scores.
Table 2. CAT score parameters of the patients with COPD
There was a significant relation between the CAT scores and the percentage of the FEV1 predicted value ( p < 0.0001). As the FEV1 decreased, the CAT score increased. As the frequency of the COPD exacerbations increased, the CAT scores ( p < 0.0001) significantly increased. There was also significant association between the exacerbation frequency and FEV1 and therefore COPD severity (p = 0.017). In the ROC analysis for assessing the ability of CAT to predict frequently exacerbator subgroup, the area under the curve (AUC) was 0.782 (95% CI 0.71–0.851), which is statistically significant ( p < 0.001).
There was a significant association between the frequency of hospitalization and the CAT scores (p = 0.001). As the hospitalization frequency increased, the FEV1 decreased ( p = 0.017) significantly. A significant relation also existed between the severity of COPD and the CAT scores ( p < 0.0001) (). In addition, there was a significant association between the severity of COPD and COPD exacerbations ( p = 0.001) as well as the severity of COPD and COPD exacerbations which required hospitalization ( p = 0.025) over the past 12 months. Frequent exacerbators had more severe COPD ( p = 0.035), higher CAT scores ( p < 0.0001), and lower FEV1 percentage of the predicted value ( p < 0.0001). The patients who had been hospitalized for an exacerbation had higher baseline CAT scores ( p = 0.003).
Figure 2. The relationship between COPD severity and CAT scores.
The association between accompanying diseases and CAT scores was not statistically significant ( p = 0.4). Associations between CAT scores and smoking ( p = 0.3), CAT scores and age ( p = 0.1) along with CAT scores and gender ( p = 0.3) were insignificant. Additionally, there was no significant association between the frequency of exacerbations and age ( p = 0.5) or the frequency of exacerbations and smoking history ( p = 0.5).
Discussion
This study assessed the effectiveness of the CAT to evaluate disease severity and exacerbation frequency in COPD patients. The CAT scores were significantly elevated as the FEV1 decreased. This demonstrated that the CAT scores reflect disease severity. In addition, we found that stable COPD patients with a history of frequent exacerbations had significantly elevated CAT scores.
To know whether shorter and easier tools like the CAT could replace the SGRQ for measuring quality of health, it is vital to determine whether they are reliable, available, and responsive for COPD populations. Previous studies have shown that the CAT is reliable (Citation1,Citation8). Jones et al. demonstrated that the correlation between the CAT scores and the SGRQ scores in 229 patients with stable COPD was very good (r = 0.80, p ≤ 0.0001) (Citation1). In a recent study, Ringbaek et al. found that the CAT and CCQ have the advantage of being easier and faster to complete than the SGRQ (Citation9). In our study, the patients completed the CAT easily however illiterate patients needed help for completing the questionnaire.
This instrument is now being used in an increasing number of countries and the performance results have been similar (Citation8). The Turkish version of the CAT is a validated health status questionnaire that is free to use (Citation3). Yorgancıoğlu et al. studied COPD patients with a mean age of 62.4 (SD 8.9), a mean FEV1 predicted 51.9 (SD 19.2)%, with a mean CAT score 17.8 (SD 9.5). The distribution of the patients according to GOLD stages were; moderate 45%, severe 34%, very severe 10.2%, totally 44.2% severe and very severe patients. In our study, the mean age was 65 (SD 9.9), the mean FEV1 predicted was 43.7% and the mean CAT score was 21. We had 33% moderate, 42% severe and 21% very severe patients, totally 63% severe and very severe. Our patients were older, their pulmonary functions were worse and their GOLD stages were higher than the other Turkish study.
So, we believe that this could be the reason about the variability of data between these two Turkish studies (Citation3). Also little variability has been exhibited in the CAT across countries. A study using the Arabic version of the CAT conducted with 45 participants showed a mean total (± SD) score at the test session of 10.7 ± 5.8 and 9.2 ± 4.5 at the re-test session. They found the Arabic version of the CAT was easy to administer and reliable (Citation10). A study from Beijing showed that the Chinese version of the CAT had good internal consistency, reliability, and validity and that it can be used to assess the quality of life for Chinese COPD patients (Citation11). By using the Turkish version of the CAT, we demonstrated that elevated CAT scores reflect disease severity. We found a very strong correlation between the CAT scores and FEV1 in our patient population. We also found the Turkish version was easy to use. It also provided an accurate reflection of disease severity and was a good instrument for determining the quality of life of Turkish COPD patients.
Previous studies have shown that the CAT is responsive to changes in COPD health status during recovery following a COPD exacerbation and in response to pulmonary rehabilitation (Citation12). A more recent study showed that CAT scores improved in response to pulmonary rehabilitation and they also indicated the degree of response (Citation13).
Patients with a history of frequent exacerbations have a worse quality of life along with an increased risk of hospitalization and mortality (Citation14–16). Decreased FEV1 of the COPD patients was a risk factor for frequent exacerbation. However, exacerbation frequency may not be the same for COPD patients with similar FEV1 levels. Although exacerbations are generally considered to become more frequent as the severity of the underlying COPD increases, the most dependable predictor of exacerbations in an individual patient appears to be a history of exacerbations (Citation17).
For this reason, in the new GOLD guideline, frequent exacerbators were defined as a different subgroup, independent from the FEV1. A recent study showed that CAT scores can be used to evaluate exacerbation severity in COPD patients and also that baseline CAT scores were elevated in frequent exacerbators (Citation18). In our study, we showed that the baseline CAT scores in stable COPD patients are related to exacerbation frequency. We also showed that in patients with severe COPD exacerbations requiring hospitalization, the baseline CAT scores were elevated when they were examined against patients with COPD exacerbations who did not require hospitalization. In addition to these findings, further work is required to explore whether baseline CAT scores may be predictive of a frequent exacerbator subgroup of COPD patients.
There were some limitations to our study. First, many patients were taking other medications such as inhaler corticosteroids (ICS), long-acting beta agonists (LABA), long-acting anti-muscarinics (LAMA) or methylxanthines. We did not take into account the influence such medications might have had on the quality of life of the patients. Also, we used the Turkish version of the CAT, which can be accessed freely at www.catestonline.org/images/pdfs/TurkeyCATest.pdf. However, this does not guarantee that our results would be applicable to other language versions.
In conclusion, the CAT provides a reliable score of COPD severity. The CAT scores increase in stable COPD patients who have a history of frequent exacerbations. Finally, our study was a cross-sectional study that included no longitudinal changes. Therefore, in order to detect these changes, to assess the prognostic value of this tool and to evaluate the clinical effectiveness of the CAT in daily practice more detailed studies are required.
Declaration of Interest Statement
The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.
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