Reliability and Validity of the Japanese Version of the Barthel Index Dyspnea Among Patients with Respiratory Diseases

PURPOSE: Japan has only a few respiratory disease-specific activity of daily living scales that are accepted outside of Japan, and they are not widely used. The Barthel Index dyspnea (BI-d), an improved version of the Barthel Index (BI), may be popular in Japan. The purpose of this study was to develop the Japanese version of BI-d (J-BI-d) and investigate its reliability and validity. PATIENTS AND METHODS: The J-BI-d was developed using the basic guidelines for scale translation. The study included patients with chronic respiratory disease, receiving outpatient care at two centers between January 2019 and February 2020. Scores on the J-BI-d, modified Medical Research Council scale (mMRC scale), BI, respiratory function tests, and 6-minute walk distance (6MWD) test were measured. To verify the test–retest reliability, the J-BI-d was re-administered, and the intraclass correlation coefficient (ICC) was obtained. Internal consistency was verified by Cronbach’s alpha reliability coefficient, and criterion-related validity was verified through a correlation analysis of the J-BI-d with mMRC scale and 6MWD test. Divergent validity was verified through correlation analysis between the J-BI-d and BI. RESULTS: Data for 57 participants (mean age 74.4 ± 8.3 years) were analyzed, and reliability testing was performed with 42 of them. The mean time to retest was 8.1 ± 3.0 days, and the ICC (2, 1) was 0.76 (95% CI: 0.62–0.85), indicating high reliability. Cronbach’s alpha reliability coefficient was 0.81, indicating high internal consistency. Correlation coefficients of the J-BI-d with 6MWD test (r = −0.46, p < 0.01) and mMRC scale (ρ = 0.76, p < 0.01) indicated high criterion-related validity. The J-BI-d and BI had a weak negative correlation (r = −0.29, p < 0.05), indicating high divergent validity. CONCLUSION: The results of this study demonstrate high reliability and appropriate validity of the J-BI-d in patients with chronic respiratory disease.