Is EQ-5D a valid quality of life instrument in patients with Parkinson's disease? A study in Singapore.
BACKGROUND
The purpose of the present study was to evaluate the validity of the EQ-5D in patients with Parkinson's disease (PD) in Singapore.


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 Chinese-speaking patients with PD should be further assessed.
Luo
Nan
N
Epidemiology and Public Health & Centre for Health Services Research, Yong Loo Lin School of Medicine, National University of Singapore, Singapore. ephln@nus.edu.sg
Low
Serena
S
Lau
Puay-Ngoh
PN
Au
Wing-Lok
WL
Tan
Louis C S
LC
D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000503:physiopathology*; D011788:Quality of Life; D012846:Singapore; D011795:Surveys and Questionnaires / Q000592:standards*