Uncovering indicators of the international classification of functioning, disability, and health from the 39-item Parkinson's disease questionnaire.
The 39-item Parkinson's disease questionnaire (PDQ-39) is the most widely used patient-reported rating scale in Parkinson's disease (PD). However, recent studies have questioned its validity and it is unclear what scores represent. This study explored the possibility of regrouping PDQ-39 items into scales representing the International Classification of Functioning, Disability, and Health (ICF) co
