Parkinson's Disease Research Today is a free monthly online journal that collates and summarizes the latest research about Parkinson's Disease, including details on symptoms, treatment, genetics, medication.

Validation of PDQ-8 as an independent instrument in English and Chinese.

Tan LC, Lau PN, Au WL, Luo N

Department of Neurology and Parkinson's Disease and Movement Disorders Centre, National Neuroscience Institute, USA National Parkinson Foundation Centre of Excellence, 11 Jalan Tan Tock Seng, Singapore 308433, Singapore. louis_tan@nni.com.sg

Previous validation studies on the PDQ-8, a brief disease-specific quality of life instrument, were performed with the PDQ-8 nested in the original PDQ-39. Such an approach may influence patient responses and the psychometric properties of the PDQ-8. We therefore undertook this study to validate the PDQ-8 when administered independently in English and Chinese and found good item-to-scale correlations (correlation coefficient: 0.44-0.68) and internal consistency (Cronbach's alpha: 0.81, 0.87). Factor analyses yielded a component on which all 8 questions were substantially loaded (loading range: 0.55-0.77). Scree plots also showed the one-factor solution thereby validating the PDQ-8 summary index. Construct validation against the Hoehn and Yahr stage and UPDRS motor scores showed significant correlations between higher PDQ-8 summary index and increased disease severity in both English and Chinese versions. Our results show the PDQ-8 to be a valid and reliable disease-specific HRQoL instrument for PD when used independently of the PDQ-39.

Published 22 March 2007 in J Neurol Sci, 255(1): 77-80.
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