Psychometric Properties of the Persian Version of Penn Parkinson Daily Activities Questionnaire-15

Appropriate information about the ability of patients with Parkinson disease (PD) to perform cognitive instrumental activities of daily living (IADL) is necessary. The present study aimed to assess the psychometric properties of the Persian version of the Penn Parkinson daily activities questionnaire-15 (PDAQ-15).

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 used in the study. Internal consistency and test-retest reliability were evaluated by the Cronbach α 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 the Spearman rank correlation test. To assess the discriminative validity, PDAQ-15 scores were compared across cognitive stages.

The PDAQ-15 showed strong internal consistency (the Cronbach α=0.99) and test-retest reliability (ICC= 0.99). Only one dimension was identified for the PDAQ-15 in the factor analysis. There was a strong correlation between PDAQ-15 with the depression domain of the HADS scale and the Lawton IADL scale (rs=|0.71–0.95|). The correlation of PDAQ-15 with the anxiety domain of the 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.

These results suggest that the PDAQ-15 is a valid and reliable PD-specific instrument and can be useful in clinical and research settings.