Agreement of the modified Medical Research Council and New York Heart Association scales for assessing the impact of self-rated breathlessness in cardiopulmonary disease

Background The functional impact of breathlessness is assessed using the modified Medical Research Council (mMRC) scale for chronic respiratory disease and with the New York Heart Association Functional Classification (NYHA) scale for heart failure. We evaluated agreement between the scales and their concurrent validity with other clinically relevant patient-reported outcomes in cardiorespiratory disease. Methods Outpatients with stable chronic respiratory disease or heart failure were recruited. Agreement between the mMRC and NYHA scales was analysed using Cramer's V and Kendall's tau B tests. Concurrent validity was evaluated using correlations with clinically relevant measures of breathlessness, anxiety, depression, and health-related quality of life. Analyses were conducted for all participants and separately in chronic obstructive pulmonary disease (COPD) and heart failure. Results In a total of 182 participants with cardiorespiratory disease, the agreement between the mMRC and NYHA scales was moderate (Cramer's V: 0.46; Kendall's tau B: 0.57) with similar results for COPD (Cramer's V: 0.46; Kendall's tau B: 0.66) and heart failure (Cramer's V: 0.46; Kendall's tau B: 0.67). In the total population, the scales correlated in similar ways to other patient-reported outcomes. Conclusion In outpatients with cardiorespiratory disease, the mMRC and NYHA scales show moderate to strong correlations and similar associations with other patient-reported outcomes. This supports that the scales are comparable when assessing the impact of breathlessness on function and patient-reported outcomes.