Validity and reliability of the Japanese and Chinese versions of COOP/WONCA charts
The Chinese version of the COOP/WONCA charts  had already been shown to be reliable and valid for nervous system diseases, orthopedic disease, cancer, and strokes in China. Patients’ acceptance of the test is high, and the test is useful for the doctors who are evaluating them [16, 23]. Although the Japanese version of the COOP/WONCA charts has been used to measure quality of life in the field of ophthalmology , and as a health survey and to measure quality of life in pediatrics [25, 26], its reliability and validity have not been fully confirmed in an adult Japanese population. In our study, we enrolled subjects ages 50-79 years because the target of this study was patients with COPD, and the incidence of COPD increases with age. We verified the reliability and validity of the COOP/WONCA chart in Japanese and Chinese groups of healthy subjects and patients with COPD.
The “Feelings” and “Daily activities” COOP/WONCA charts showed high correlation with the mental component scores of the SF-36 in the Japanese population and the physical component scores of the SF-36 in the Chinese population. “Change in health”, which asks about changes in health status compared with that of the previous two weeks, was correlated with the physical component of SF-36 in both groups, but most with “physical functioning” in the Japanese group and most with “bodily pain” in the Chinese group. Other than these differences, the correlation of the COOP/WONCA charts and the subscales of SF-36 were consistent between the Japanese and Chinese groups. These results suggest that the Japanese and Chinese versions of the COOP/WONCA charts are appropriate for evaluating the health status of older healthy subjects and patients with COPD. The reproducibility of the COOP/WONCA charts, except for “Change in health”, was confirmed: in the test-retest, the ICC of each item was in the range of 0.657 to 0.890 in both the Japanese and Chinese populations.
We evaluated external validity and sensitivity by correlating the patient's evaluation with their doctor’s evaluation using the same COOP/WONCA charts, the number of respiratory symptoms associated with COPD, and the COPD status. After the subjects were matched on sex and age, the correlation coefficient between patients and their doctors was > 0.527 in the Japanese group, except for the “Pain” chart, and > 0.826 in the Chinese group for all of the items.
The Japanese patients with COPD gave higher scores on the “Pain” item than the doctor’s evaluation did, indicating that the doctor had underestimated the pain the patients felt. This discrepancy may be due in part to Japanese characteristics such as stoicism. The significant correlations of the COOP/WONCA chart items with the number of respiratory symptoms associated with COPD and with COPD status support the external validity of the charts. However, there were two aspects of the COOP/WONCA charts that differed between the Japanese and Chinese subjects. One was that there was no significant correlation between “Pain” and the number of respiratory symptoms of COPD in the Japanese group; the other was that all of the items, except “Change in health”, showed higher correlation with BI in the Chinese group than in the Japanese group. Pain control may have been more complete in Japanese patients with COPD than in Chinese patients. The reasons for the low correlation between BI and COOP/WONCA charts in the Japanese population are not clear. Cigarette type, smoking habits, and the tobacco smoking environment surrounding the patient may have contributed to these differences in the Japanese and Chinese groups.
To clarify the determinants of the COOP/WONCA chart items, we performed stepwise multiple regressions, adjusting by nationality, age, sex, COPD status, number of respiratory symptoms, and heating sources. The COPD status, the number of respiratory symptoms, or both were predictive variables for all of the items except “Change of health”. This result suggests that the health status measured by the COOP/WONCA charts reflected the levels and conditions of COPD patients. In addition, those scores on all items except “Feelings” and “Overall health” could be compared between the Japanese and Chinese populations according to the result from stepwise multiple regression analyses. Although nationality was a predictive variable for “Feelings” and “Overall health”, the scores for “Feelings” among healthy subjects were better in the Chinese group than in the Japanese group, whereas for the COPD patients, the “Overall health” score was better in the Japanese group than in the Chinese group. The social environment surrounding the patients, lifestyle, cultural and religious background, and medical treatments may influence “Feelings” and “Overall health” in complicated ways. It is necessary to analyze this point in more detail. The reliability and validity of the English version of the COOP/WONCA charts has been tested with COPD patients. Stavem and Jodalen  observed high correlation between items on the COOP/WONCA charts and the EuroQol 5-Dimension (EQ-5D) test in 59 male and female outpatients with COPD (average age 57 years old). The authors suggested that the reliability of the COOP/WONCA items was acceptable for use at the group level, but lower than current recommendations for use in individual patients. In contrast, Eaton et al.  found that the Dartmouth COOP charts were reliable, valid, and responsive compared with the SF-36, Chronic Respiratory Questionnaire (CRQ), and Hospital Anxiety and Depression (HAD) questionnaires in a comparative study of oxygen therapy for patients with COPD, who were on average 68.3 years old. The authors showed that these charts are a simple, reliable health-related quality-of-life tool that was valid and responsive in their population of COPD patients and may have a valuable role in routine clinical practice. Our results also suggested that the Japanese and Chinese versions of the COOP/WONCA charts provide good reliability and validity for measuring health status and for comparing healthy subjects and patients with COPD in Japanese and Chinese populations.
Comparison of health status in Japanese and Chinese patients with COPD by using COOP/WONCA charts
1. In our Japanese subjects, patients with COPD showed almost the same health status as healthy subjects of the same age, when stratified by sex, age, and COPD status (Table 6). However, although the healthy Chinese subjects had clearly higher health status than the Japanese subjects, the health status declined in proportion to GOLD stage in patients with COPD. In particular, for Chinese subjects, the physical score and daily and social activity scores were worse in the patients with moderate COPD than in the healthy subjects, and the pain and psychological health status worsened further in the patients with severe COPD. The poor “Overall health” in the patients with severe COPD may reflect the strong deterioration of physical and social activity and psychological performance.
Few studies have used the COOP/WONCA charts to evaluate chronic disease and health status in COPD patients and have compared the results between countries. There is only one report that we know of that compared the results of a factor analysis of COOP/WONCA charts at primary care clinics in four countries and showed the average scores on each item and the 95% confidence interval . The authors suggested that the COOP/WONCA system was suitable for general use in primary care internationally.
The present study clarified that although healthy Chinese 50- to 79-year-olds have higher health status than corresponding Japanese people, the health status of Chinese patients with COPD decreases as symptoms get worse. Because a high positive correlation was observed between indoor use of smoky fuels and “Daily activity” and “Social activity” scores in the Chinese group, use of these fuels may be one of the precipitating factors of COPD in the Chinese population. More than 20% of Chinese males and females in this study were using coal or biomass indoors; indoor use of smoky fuels was associated with worse respiratory symptoms, which restrained physical and social activity. Diette et al.  reviewed the relation of biomass combustion exposure in an indoor environment and pulmonary obstructive disease, and found that combustion of biomass or coal indoors can lead to a fall in pulmonary function and aggravation of COPD. Therefore, the use of indoor heating and cooking equipment that does not produce smoke and the avoidance of cigarette smoking may improve physical and social activity and psychological levels as well as medical treatment, including pain control. Future studies should analyze risk factors related to health status in patients with COPD in the Chinese population. Aging and air pollution are increasing rapidly in Asia, which will likely increase the rate of COPD disease and related mortality. Immediate action to reduce risk factors leading to COPD may be required for improving the health economic and social burdens caused by the disability-adjusted life years lost due to COPD.