Psychometric properties of the Anxiety Inventory for Respiratory Disease in patients with COPD in China

BACKGROUND: Anxiety is a common comorbidity in patients with COPD in China, and it can significantly decrease patients’ quality of life. Almost all anxiety measurements contain somatic items that can overlap with symptoms of COPD and side effects of medicines, which can lead to bias in measuring anxiety in patients with COPD. Therefore, a brief and disease-specific non-somatic anxiety measurement scale, the Anxiety Inventory for Respiratory Disease (AIR), which has been developed and validated in its English version, is needed for patients with COPD in China. METHODS: A two-center study was conducted in two tertiary hospitals in Tianjin, China. A total of 181 outpatients with COPD (mean age 67.21±8.10 years, 32.6% women), who met the inclusion and exclusion criteria, were enrolled in the study. Test–retest reliability was examined using intraclass correlation coefficients. The internal consistency was calculated by Cronbach’s α. Content validity was examined using the Content Validity Index (CVI), scale-level CVI/universal agreement, and scale-level CVI/average agreement (S-CVI/Ave). Besides, convergent validity and construct validity were also examined. RESULTS: The AIR-C (AIR-Chinese version) scale had high test–retest reliability (intraclass correlation coefficient =0.904) and internal consistency (Cronbach’s α=0.914); the content validity of the AIR-C scale was calculated by CVI, scale-level CVI/universal agreement, and S-CVI/Ave at values of 0.89–1, 0.90, and 0.98, respectively. Meanwhile, the AIR-C scale had good convergent validity, correlating with the Hospital Anxiety and Depression Scale-Anxiety (r=0.81, P<0.01), and there were significant correlations between the AIR-C and Clinical COPD Questionnaire (CCQ; r=0.44, P<0.01) and Activities of Daily Living Scale (ADLS; r=0.36, P<0.01). A two-factor model of general anxiety and panic symptoms in the AIR-C scale had the best fit according to Confirmatory Factor Analysis (CFA). CONCLUSION: The AIR-C scale had a good reliability and validity for patients with COPD and can be used as a user-friendly and valid tool for measuring anxiety symptoms among patients with COPD in China.