PDQ-39: a review of the development, validation and application of a Parkinson's disease quality of life questionnaire and its associated measures.

Parkinson's disease is a common degenerative neurological condition. A number of general instruments exist to measure quality of life, but these were not designed to address areas salient to a specific disease. This contribution reviews the development and validation of the PDQ-39, a short 39-item quality of life questionnaire for Parkinson's disease. PDQ-39 data can be presented either in profile form or as a single index. This report also reviews the development and validation of a briefer measure (PDQ-8) derived from the PDQ-39, and of two summary indices (PDQ-39SI and PDQ-8SI.