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

• DOI: 10.1016/j.jns.2007.01.072
• Publication Date: 2007-03-03T18:24:45Z
• Authors: Louis C.S. Tan; Puay-Ngoh Lau; Wing-Lok Au; Nan Luo
• Keywords: Quality of life; Male; PDQ-39; Singapore; Parkinson's disease; Reproducibility of Results; Parkinson Disease; PDQ-8; Middle Aged; Neuropsychological Tests; 03 medical and health sciences; 0302 clinical medicine; Asian People; Predictive Value of Tests; Surveys and Questionnaires; Disease Progression; Quality of Life; Humans; Female; Aged; Language

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.