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.