Comparison between tools for measuring breathlessness: Cross-sectional validation of the Japanese version of the Dyspnoea-12

Introduction The Dyspnoea-12 (D-12) is a brief, easy to complete questionnaire for measuring breathlessness. Objectives To facilitate further efforts to measure dyspnoea in real clinical settings, the authors aimed to develop and validate a Japanese version of the D-12 and also compare the D-12 with the Baseline Dyspnea Index (BDI) and the Activity component of the St. George's Respiratory Questionnaire (SGRQ). Methods The standardized procedure in accordance with international guidelines was used to create the translation. A validation study with a cross-sectional observational design was conducted on 122 subjects with stable chronic obstructive pulmonary disease (COPD). Results The internal consistency of the D-12 was high (Cronbach's coefficient alpha = 0.883) and similar to that of the BDI (alpha = 0.824) and SGRQ Activity (alpha = 0.872). The relationships between tools were statistically significant (|R-s| = 0.53 to 0.66). Although the scores obtained from all three tools were skewed toward the milder end of the respective scales, this deviation was most prominent in the D-12 with a floor effect of 48.4%. Conclusion The Japanese version of the D-12 was successfully validated, but we should be careful of any floor effect and marked skew to the mild end of the scale, especially in subjects with mild COPD.