Psychometric properties of the Japanese version of the Kansas City Cardiomyopathy Questionnaire in Japanese patients with chronic heart failure

BACKGROUND: Heart failure is a worldwide health problem that significantly affects patients' physical function and health state. The Kansas City Cardiomyopathy Questionnaire (KCCQ) is a disease-specific patient-reported outcome measure commonly used for the assessment of health states of patients with heart failure. This study aimed to evaluate the psychometric properties of the Japanese version of the KCCQ. METHODS: Using pooled data of 141 Japanese patients with chronic heart failure from three clinical trials, the Japanese version of the KCCQ was evaluated for validity and reliability, with a focus on the clinical summary score (CSS) and its component domains. For construct validity, the associations of baseline KCCQ scores with New York Heart Association (NYHA) class and the EuroQol five-dimension, three-level (EQ-5D-3L) scores at baseline were analyzed. For reliability, internal consistency was assessed using Cronbach's α, and test-retest reliability (reproducibility) was assessed among stable patients. Responsiveness to changes in patients' clinical status was assessed by analyzing score changes between two timepoints among patients whose health states improved. RESULTS: Among 141 patients (mean age, 73.7 ± 10.9 years), 76.6% were NYHA class II at baseline. For CSS and its component domains (physical limitations, symptom frequency, and symptom severity), baseline scores were all significantly lower in patients with a higher NYHA class (p < 0.001 for all, Jonckheere-Terpstra test). The physical limitations domain and CSS showed a moderate correlation (Spearman's ρ = - 0.40 to - 0.54) with three functional status-related EQ-5D dimensions (mobility, self-care, and usual activities). The Cronbach's standardized α was high (> 0.70) for all KCCQ domain/summary scores. In the test-retest analysis among 58 stable patients, all domain/summary scores minimally changed by 0.3-4.2 points with intraclass correlation coefficients of 0.65-0.84, demonstrating moderate to good reproducibility, except for the symptom stability domain. Among 44 patients with improved health states, all domain/summary scores except for the symptom stability and self-efficacy domains substantially improved from baseline with a medium to large effect size of 0.62-0.88. CONCLUSIONS: The Japanese version of the KCCQ was demonstrated to be a valid and reliable tool for the assessment of symptoms and physical function of Japanese patients with chronic heart failure.