Cross-cultural evaluation of the short form 8-item Parkinson's disease questionnaire (PDQ-8): Results from America, Canada, Japan, Italy and Spain

Objective: The purpose of this study was to evaluate the psychometric properties of a short form health survey, the Parkinson's Disease Questionnaire (PDQ-8), cross-culturally, by comparing results gained from this instrument to the original longer form instrument-the PDQ-39. Design: Data are from the Global Parkinson's Disease Survey. Outcomes: The 8-item Parkinson's Disease Questionnaire Single Index Score (PDQ-8-SI). In this study, we evaluate response rate, scaling assumptions, and data quality, in terms of comparability of results with the parent form from which the PDQ-8 was derived, of the instrument in the USA, Canada, Spain, Italy and Japan. Results: The PDQ-8 was found to produce results that were very similar to the parent form across all five countries. However, it should be borne in mind that the PDQ-8 was nested within the PDQ-39, and results may be influenced by this. Conclusions: Results suggest that the PDQ-8 is a valid and reliable measure that can be appropriately and meaningfully used in cross-cultural studies. (c) 2006 Elsevier Ltd. All rights reserved.