Evaluation of Reliability and Validity of PDQ39: Questionnaire in Iranian Patients With Parkinson’s Disease

Background Parkinson’s disease is a progressive neurological disease. Measuring quality of life in these patients could be a useful tool for evaluation and prioritization of care services. The 39item Parkinson’s Disease questionnaire (PDQ39) is an acceptable measure to assess quality of life in these patients. Objectives This study aims to assess the validity and reliability of the Persian version of PDQ39 questionnaire. Patients and Methods In this crosssectional study, Persian version of questionnaire was prepared with translation, back translation, cognation debriefing and culture adaptation. One hundred four Parkinson’s disease patients referred to Shahid Motahari clinic affiliated to Shiraz University of Medical Sciences were included in the study. Then PDQ39 and general quality of life questionnaire (36Item short form health survey: SF36) were completed by trained interviewers. The reliability of the questionnaire was measured through Cronbach’s alpha coefficient. Construct validity assessed by itemscale correlation method and criterion validity was determined by discriminant validity and convergenent validity methods. Results Range of Cronbach’s alpha coefficient for different dimensions varied from 0.64 to 0.92. Cronbach’s alpha coefficient was higher than 0.70. Itemconvergent validity ranged from 0.38 to 0.83. Similar dimensions of PDQ39 and SF36 questionnaire were highly correlated. The quality of life among higher stage patients was lower (P amp;lt; 0.001). Conclusions Findings showed reliability and validity of Persian version of PDQ39 is acceptable. It can be used to measure health related quality of life in Persianspeaking Parkinson’s disease patients.