• Vol. 38 No. 6, 521–528
  • 15 June 2009

Is EQ-5D a Valid Quality of Life Instrument in Patients With Parkinson’s Disease? A Study in Singapore



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Introduction: The purpose of the present study was to evaluate the validity of the EQ-5D in patients with Parkinson’s disease (PD) in Singapore. Materials and Methods: In a cross-sectional survey, patients with PD completed English or Chinese version of the EQ-5D, the 8-item Parkinson’s disease questionnaire (PDQ-8), and questions assessing socio-demographic and health characteristics. Clinical data were retrieved from patients’ medical records. The validity of the EQ-5D was assessed by testing a-priori hypotheses relating the EQ-5D to the PDQ-8 and clinical data. Results: Two hundred and eight PD patients (English speaking: 135) participated in the study. Spearman correlation coefficients between the EQ-5D and PDQ-8 ranged from 0.25 to 0.75 for English-speaking patients and from 0.16 to 0.67 for Chinese-speaking patients. By and large, the EQ-5D scores were weakly or moderately correlated with Hoehn and Yahr stage (correlation coefficients: 0.05 to 0.43), Schwab and England Activities of Daily Living score (correlation coefficients: 0.10 to 0.60), and duration of PD (correlation coefficients: 0.16 to 0.43). The EQ-5D index scores for patients with dyskinesia or “wearing off” periods were significantly lower than those without these problems. The EQ-5D Visual Analog Scale (EQ-VAS) scores also differed for English-speaking patients with deferring dyskinesia, “wearing off” periods, or health transition status; however, such differences were not observed in patients who completed the survey in Chinese. Conclusions: The EQ-5D questionnaire appears valid for measuring quality of life in patients with PD in Singapore. However, the validity of EQ-VAS in Chinesespeaking patients with PD should be further assessed.

The EQ-5D is a preference-based, generic instrument that measures quality of life in three different ways.1 The first part is a descriptive system providing a profile of respondents’ health status in five dimensions. The second measure is a 0 to 100 visual analog scale for self-rating of own health. Thirdly, an index score can be generated to reflect the preference or utility of the measured health profile from the perspective of the general population. The EQ-5D index score is a legitimate measure of health outcomes necessarily for quality-adjusted life years (QALYs) calculation and cost-utility analysis (CUA) in economic evaluation of health technologies and interventions.2,3

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