Chronic obstructive pulmonary disease (COPD) refers to progressive respiratory conditions including emphysema and chronic bronchitis, It is characterized by cough, difficulty breathing, and airflow limitations, which are commonly associated with smoking (1). COPD is considered a common global health problem with an estimated prevalence of 10% and a substantial disease burden (2). It was the fourth cause of mortality in 1990, changed to third in 2010. It was reported that 90% of this disease occurs in low- and middle-income countries (3).
COPD significantly impairs patients' health-related quality of life (HRQOL). It was ranked among the top five diseases affecting patients' Quality of Life (QOL) in 2020 (4). One of the crucial features of the disease associated with QOL and mortality is disease exacerbations, which should be appropriately managed (5). Therefore, the evaluation of HRQOL is considered an essential step for patients' management and policy-making (6). In randomized controlled trials, the primary outcome is usually the change in mean forced expiratory volume in the first second (FEV₁) resulting from treatment. However, the functional measures that physicians might consider for management decisions may not be related precisely to the perception of the disease by the patient. In recent years, patient-reported outcomes (PROs) have been considered essential (7). Most COPD trials used lung function )usually FEV₁( as the primary outcome. Whereas physicians usually make changes to therapy based on patients' symptoms. This leads to the development of PROs as methods for evaluating clinical information (8). This information is used to assess the efficacy of indacaterol and dual combination bronchodilators to improve the health status of COPD patients (9).
General questionnaires, like the Short Form Health Survey (SF-36), can only show the general QOL of patients. However, disease-specific questionnaires are more commonly used, as they specifically address the features of the target disease (10). The St. George's Respiratory Questionnaire (SGRQ) was designed by Jones et al. (11) to evaluate patients' health status with airway diseases and was used to measure the health status of patients with COPD. This standard questionnaire has been translated into several languages, such as Spanish (12), Swedish (13), and Chinese (14), with acceptable validity and reliability (Cronbach's coefficient alpha (α) >0.7) and have been used to investigate different conditions, such as patients with bronchiectasis (15), asthma (14), and COPD (13, 16). Although the Persian version of the SGRQ was also validated (17). The St. George's Respiratory Questionnaire for COPD patients (SGRQ-C) is a shorter version of the SGRQ, derived from the original version. It is valid for COPD, however, has not yet been validated in Persian. Due to the increasing COPD-related mortality in Iran and the tremendous economic burden caused by the disease in this country (18), we aimed to validate a standard measure for assessing COPD patient outcomes in Persian to provide a broader view of the health status of Iranian patients with COPD.

 

The test for internal consistency revealed a Cronbach's coefficient alpha of 0.641 and 0.642 for the whole questionnaire and the first part of the questionnaire (questions 1-7), respectively, and excellent internal consistency for the second part (questions 8-14) (Cronbach's coefficient alpha = 0.901). A correlation ≥ 0.7 indicated that questions are likely to measure the same construct (24). According to the reliability calculation after deleting each question, it was observed that Cronbach's coefficient alpha increased to 0.732 if question 4 was deleted.
After consultation with a panel of 5 experts, the CVR was 1 for questions 1-13, so they were valid, and 0.6 for question 14 (25). After validation of the questionnaires, it was finally completed by 158 participants. The results of assessing patients' health status by the questionnaire are as follows:
The current health was scored as very good, good, fair, poor, and very poor in 7.6%, 22.2%, 44.9%, 22.8%, and 2.5% of the patients, respectively (Figure 1).
 

 
Figure 1. The frequency of the participant's answers to the general questions of current health status in St.George's Respiratory Questionnaire.

 
The sum of symptoms was 306.98, and the mean±SD score calculated for a symptom was 54.216±23.725%. The mean±SD of the sum of activity was 476.26, and the mean±SD score calculated for activity was 48.45±27.22%. The sum of impact was 619.51, and the mean±SD score calculated for impact was 37.48±26.390%. The total sum was 1405.20, and the mean±SD score calculated for the total score was 43.89±23.62% (Table 1).

Table 1. Demographic and the scores of the St. George's Respiratory Questionnaire of the studied patients

Values are presented as means±SD. BMI=body mass index.
 

A significant negative correlation was found between symptom, activity, total score, and FEV₁. A significant positive correlation was found among all sub-scales of SGRQ-C. Body Mass Index (BMI) did not correlate with domains of SQRQ-C (Table 2). A negative correlation between age and symptom score (r=-0.543, p<0.01) in the subgroup of patients with FEV₁≥65% (Table 2) was found.

** P value<0.01, *   P value<0.05, r Values and p values were obtained by Spearman
rank correlation analysis

Discussion

The results of the first phase of the present study on the validation of SGRQ-C in Persian indicated excellent reliability (>0.9) in the second part. The Cronbach coefficient of 0.64 in the first part and in total was obtained which increased after deleting question 4. This question addressed the time of wheezing, which might be shown inaccurately by patients due to inattention or forgetting the time of the incident. Moreover, the reason could be the incomplete knowledge of patients in the present study on the correct definition or diagnosis of wheezing. The SGRQ has been validated in more than 35 languages, but the reliability coefficients varied in different languages. The Chinese version of the SGRQ indicated similar results to our study Chan et al. (26) reported Cronbach's coefficient>0.7, except in symptoms (Cronbach's coefficient of 0.6). Although they evaluated patients with bronchiectasis, we focused on patients with COPD. The American version of the SGRQ in COPD patients also reported a Cronbach's coefficient>0.7 for all dimensions, except symptoms (16). These results may suggest that although the COPD-specific questionnaire has acceptable reliability in UK/English and is similar to the original version (27), the translations in different languages do not have the same high reliability. The reasons for these differences could be due to the disease characteristics in different nations, which also can vary based on social and cultural contexts, gender, ethnicity, lifestyle, education levels, professional skills, and knowledge disparities among COPD patients (28, 29).
The results of the second phase of the present study indicated that the current health status of participants was very good in about 8%, good in 22%, fair in 45%, poor in 23%, and very poor in 2.5% of the participants. The mean±SD scores calculated for a symptom, activity, impact, and the total score were 54.216±23.725, 48.45±27.22, 37.48±26.39, and 43.89±23.62, respectively. Although the majority of participants had marked their current health status as not poor or very poor, the reported scores indicated inappropriate HRQOL in the studied patients. It might be due to the lack of knowledge of the patients about the different dimensions of their disease. Ferrer et al. (20) reported the mean SGRQ scores in normal subjects in a general Spanish population and reported the normal scores of participants without COPD at 12, 9, 2, and 6, for symptom, activity, impact, and total scores, respectively. They reported variations in these scores according to patients' age, sex, educational level, and concomitant diseases like asthma, and smoking status. In another similar study on 1817 patients with COPD, Jones et al. (6) reported a mean total SGRQ score of 44.7±19.4 and interpreted it as a marked impairment of HRQL. They declared that the total scores varied from about 40 to 50 according to the studied countries (6). In addition, Tashkin et al. (30) reported a mean total score of about 46 on about 6000 patients. Rutten-van Mölken et al. (31) found a total mean score of 48-50 in different drug groups. In a study on 37 COPD patients in Iran by Mirdamadi et al. (32), the total SGRQ score was 44.5±22.1 and negatively correlated with FEV₁.
Although the total score reported in the present study was much higher than (6, 30, 31), the mean score of symptom dimension (54.2) was lower than the Jones' study (6) and even in patients at the first stage of COPD (56.2). It was similar to Rutten-van Mölken's study (31) in the placebo group (54.4) and in the salmeterol+ipratropium bromide group (54.0. Also, the mean activity score in the present study was 48.45, which was less than the above-mentioned studies, even in patients in the first stage of COPD (47.6). It was much less than that of Rutten-van Mölken's study (64-65 in different groups) (31). Furthermore, the mean impact score of the present study (37.4) was similar to the salmeterol+ipratropium bromide group in the study by Rutten-van Mölken et al. (31). At the same time, it was much higher than that in Jones' study, reporting the mean impact score at different disease stages ranging from 27.8 to 33 (6). These variations can be attributable to different patients and disease characteristics between studies. Considering that the minimum clinically significant difference in SGRQ is set at four units (33), paying attention to these values is of great importance. In view of the inappropriate health status of the studied patients, it is necessary to implement effective measures for improving the HRQOL of patients with COPD at this center.
One of the crucial issues in assessing the HRQOL of patients with COPD is the different variables affecting it (28). A study in Iran has suggested that patients' socioeconomic status and income are essential predictors of HRQOL in COPD patients (34). In addition, the disease severity, the presence, and the number of concomitant comorbidities are considered essential predictors of HRQOL in patients with COPD (6, 35). Therefore, differences between the studies worldwide may not specifically be attributed to the difference in the patient's HRQOL but may be due to the differences in patients' characteristics, disease features, and socioeconomic status, as explained above.
The limitation of the present study was the selection of samples from a single center that might not be representative of the general population limiting the generalizability of the results. However the study contained all of the patients with stable COPD followed in the hospital during their illness period with different severity of disease, the response rate was good, and patients consented and wanted to complete the questionnaire.

 

Conclusion

The present study results showed that the Persian version of SGRQ-C had acceptable reliability and validity and could be used in Iranian patients with COPD. The results of assessing the health status of 158 patients with COPD showed that only about 25% of them had poor or very poor current health status. The majority (75%) considered their current health status desirable. However, the scores of three dimensions, including symptom, activity, and impact, were relatively high. The total score was inappropriate as well, which indicated impaired HRQOL in these patients and called for greater attention to the health status of these patients and implementing the necessary measures for better management and patient care at the study center. Future multicentric studies can investigate Iranian patients from different cities and ethnicities to examine the differences and predictors of the health status of patients with COPD across the country.

 

Acknowledgements

The authors of the present study sincerely thank the personnel of the Pulmonary Function Laboratory of Shahid Faghihi Hospital and the Clinical Research Development Center of Namazi Hospital.

 

Conflicts of Interest

The present study's authors declare that they have no conflicts of interest.