Quality of life in Parkinson's disease: Italian validation of the Parkinson's Disease Questionnaire (PDQ-39-IT)

Translation and cross-cultural adaptation of the 39-item Parkinson's Disease Questionnaire (PDQ-39) to the Italian culture was performed by Oxford University Innovation in 2008, but this version has never been validated. Therefore, we performed the process of validation of the Italian version of the PDQ-39 (PDQ-39-IT) following the Consensus-Based Standards for the Selection of Health Status Measurement Instruments checklist. The translated PDQ-39-IT was tested with 104 patients diagnosed with Parkinson's disease (PD) who were recruited between June and October 2017. The mean age of the participants was 65.7 +/- 10.2years, and the mean duration of symptoms was 7.4 +/- 5.3years. The internal consistency of the PDQ-39-IT was assessed by Cronbach's alpha and ranged from 0.69 to 0.92. In an assessment of test-retest reliability in 35 of the 104 patients, the infraclass correlation coefficient (ICC) ranged from 0.85 to 0.96 for the various subitems of the PDQ-39-IT (all p<0.01). Spearman's rank correlation coefficient for the validity of the PDQ-39-IT and the Italian version of the 36-Item Short Form (SF-36) was -0.50 (p<0.01). The results show that the PDQ-39-IT is a reliable and valid tool to assess the impact of PD on functioning and well-being. Thus, the PDQ-39-IT can be used in clinical and research practice to assess this construct and to evaluate the overall effect of different treatments in Italian PD patients.