Psychometric Properties of the Persian version of Penn Parkinson's Daily Activities Questionnaire-15

Introduction: There is a need to have appropriate information about the ability of Parkinson's disease (PD) patients to perform cognitive instrumental activities of daily living (IADL). The purpose of the present study was to assess the psychometric properties of the Persian version of the Penn Parkinson's Daily Activities Questionnaire-15 (PDAQ-15). Methods: A total of 165 knowledgeable informants of PD patients completed the PDAQ-15. The Clinical Dementia Rating Scale, Hoehn and Yahr staging, Hospital Anxiety and Depression Scale (HADS) and Lawton IADL scale were included in the study. Internal consistency and test-retest reliability were evaluated by Cronbach's alpha coefficient and intraclass correlation coefficient (ICC), respectively. To examine the dimensionality of the questionnaire, exploratory factor analysis was used. The construct validity was assessed using Spearman rank correlation test. To assess the discriminative validity, PDAQ-15 scores were compared across cognitive stages. Results: The PDAQ-15 showed strong internal consistency (Cronbach's α = 0.99) and test-retest reliability (ICC= 0.99). Only one dimension identified for the PDAQ-15 in the factor analysis. There was strong correlation between PDAQ-15 with depression domain of HADS scale and Lawton IADL scale. (rs = |0.71–0.95|). The correlation of PDAQ-15 with anxiety domain of HADS scale was moderate (rs = 0.66). Discriminative validity analysis showed that the PDAQ-15 has significant power to discriminate between PD patients across cognitive stages. Conclusion: These results suggest that the PDAQ-15 is a valid and reliable PD-specific instrument that can be useful in clinical and research settings.