Reliability and Validity of EQ-5D in Malaysian Population

This cross-sectional study, involving conveniently chosen respondents in the Klang Valley area, was designed to answer the question "Can EQ-5D be used as a QOL instrument in the National Health Morbidity Survey in Malaysia?". The chosen versions (Malay, Tamil, and Mandarin) of the translated EQ-5D were tested for their reliability and validity. After a written consent was obtained from each respondent, a standardized questionnaire for self-completion was given. It took an average of 10-15 min to complete the questionnaire. Each respondent who returned the completed questionnaire was approached again with an identical copy of the questionnaire to assess the test-retest reliability after a 2-week interval. Reliability was assessed by analyzing the study instrument's test-retest reliability, while a predictive validity was used to investigate the predictive strength of a composite index of the five factors of EQ-5D (mobility, self-care, usual activities, pain/discomfort, and anxiety/depression) on the overall perceived health (EQ VAS). An intraclass correlation (ICC), generated based on a single rate using the one way analysis of variance (ANOVA) model, was used to evaluate the test-retest reliability (Streiner and Norman 1995), while spearman rank correlation coefficient was used to quantify the predictive strength of a composite index of the five factors of EQ-5D on the overall perceived health (EQ VAS) (Elmes et al. 2006). It was surprising to note 1-2 folds increase in the reported cases for pain/discomfort and anxiety/depression, the same trend was observed across different versions of EQ-5D. The ICC values were found to be in the range of < 0.01 to 0.92, while 0.61-0.86 were the range for the spearman rank correlation coefficient value. The findings in this study demonstrated the EQ-5D questionnaires translated by the EuroQOL Group had reasonable test-retest reliability and predictive validity results. With these results, it is hoped that these instruments will be incorporated into future National Health Morbidity Survey in Malaysia.