Psychometric characteristics of the Parkinson's disease questionnaire (PDQ-39) - Ecuadorian version

This study sought to analyse certain metric characteristics of the Ecuadorian version (EV) of the Parkinson's Disease Questionnaire (PDQ-39 EV). A cross-sectional study was conducted on 137 Parkinson's disease (PD) patients attending a Movement Disorders Unit. Neurologists' assessments were based on Hoehn and Yahr (HY), Schwab and England and Unified Parkinson's Disease Rating Scales. Patients' self-evaluations included the Hospital Anxiety and Depression Scale, the Parkinson's Disease Quality of Life questionnaire (PDQL EV), and the PDQ-39 EV. Analyses for acceptability, internal consistency, precision, and construct validity (convergent and known-groups) were performed. Distribution of scores was satisfactory. There was no evidence of floor or ceiling effects. Although the alpha coefficient exceeded 0.70 for mobility, activities of daily living (ADL) and stigma, it was nevertheless low for bodily discomfort (0.48), communication (0.40), and social support (0.33). Fourteen items yielded low correlation coefficients (<0.40) with their respective dimensions. Correlation of social support and bodily discomfort with the Summary Index (SI) was modest (0.46 and 0.36, respectively). PDQ-39 EV SI convergent validity with the PDQL EV SI was very high (r_S=-0.91), and known-groups validity proved satisfactory. Results agreed in part with those yielded by an international study, identifying specific flaws probably linked to socio-cultural influence.