Psychometric evaluation of the Sinhalese version of MacNew Heart Disease Health Related Quality of Life Questionnaire in patients with stable angina

Background: A Sinhalese version of a validated, disease-specific patient-reported heart disease health related quality of life instrument is lacking. The purpose of this study was to validate the interviewer-administered Sinhalese version of the MacNew Heart Disease Health-related Quality of Life Questionnaire (MacNew) in patients with clinically diagnosed stable angina. Methods: The Sinhalese translation of the MacNew was carried using standard forward-backward translation technique. In this validation study, the MacNew was administered to 200 patients with stable angina. Reliability was assessed by internal consistency and test-retest reliability. Construct validity was explored by exploratory factor analysis using principal component analysis and confirmed by confirmatory factor analysis using the robust maximum likelihood method and known group comparison. The correlation between compatible domain scores of MacNew and the World Health Organization's quality of life -brief questionnaire was used to assess concurrent validity. Results: The original 3-factor model (Physical, Emotional and Social) of the MacNew with cross-loadings was confirmed: principal component analysis with 53.42 % of the explained variance and confirmatory factor analysis with adequate fit for each of the three model fit criteria considered [root mean square error of approximation = 0.044 (90 % CI = 0.031 to 0.056); comparative fit index = 0.99; chi(2)/df = 1.39]. Internal consistency of the MacNew was acceptable with Cronbach's a of 0.92 on the Global scale and on the domain scales ranging from 0.85-0.91. Test-retest reliability was also found to be satisfactory with intraclass correlation coefficients of >0.9 for total and domain scores. A satisfactory level of concurrent validity was demonstrated with statistically significant correlations between compatible domain scores of MacNew and the World Health Organization's quality of life questionnaire (Pearson correlation ranging from 0.36-0.79). Conclusions: The interviewer-administered Sinhalese MacNew is a valid and reliable patient-reported outcome measure to assess disease specific health-related quality of life among Sinhalese patients with stable angina.