Background: The Parkinson's Disease Questionnaire (PDQ-39) is a well-validated British scale for the assessment of health-related quality of life (QoL) in Parkinson's disease (PD).
Objective: To validate the Serbian version of the PDQ-39, while also providing additional information on the characteristics of this instrument.
Patient and methods: A total of 102 Serbian PD patients were asked to complete the PDQ-39, a disease-specific QoL questionnaire, as well as the generic, health status questionnaire (SF-36-version 1), and the 21-item Beck Depression Inventory. Neurological examination included the Hoehn and Yahr staging, Unified Parkinson's disease rating scale (UPDRS)-part III, Schwab and England scale, and the Mini-Mental State Examination.
Results: Internal consistency analysis yielded a Cronbach's alpha of 0.83. Cronbach's alpha was above 0.70 for seven out of eight subscales (range from 0.73 to 0.91). A hierarchical structure of the PDQ-39 was revealed, with one global higher-order factor and two lower-order factors. The strongest predictor of the QoL in PD was the presence of depression, while motor disability (UPDRS-part III score) additionally contributed to poor QoL. Cognitive impairment has not been correlated with poor QoL. Also, QoL measures were not different between young- (< or =50 years) and older-onset PD patients.
Conclusions: The PDQ-39 is a reliable and valid instrument for the assessment of QoL in Serbian PD patients.