Reliability analysis of the PDQ-39 (German version)

Aim of the study was the German translation and a reliability analysis of t he PDQ-39, a quality-of-life questionnaire for Parkinson patients originall y developed in England. 105 outpatient as well as inpatient participants we re recruited for this study. Inclusion criteria were defined as age greater than or equal to 40, Hoehn and Yahr category greater than or equal to 1 in patients with definite Parkinson's disease (UK Brain Bank Criteria). The t ranslation process was done according to the protocol of the Medical Outcom e Trust Boston. Reliability analysis included the evaluation of internal co nsistency (Cronbachs alpha), item-to-scale-correlation, test-retest reliabi lity and floor and ceiling effects. These reliability parameters of the Ger man PDQ-39 version were comparable with those of the English original. A sm all difference for Cronbachs alpha was found in only one of eight subscales of this questionnaire. Stratified analysis revealed that for this subscale differences exist between outpatients and inpatients. The German version a llows to use the PDQ-39 in German-speaking countries and facilitates the st udy of health-related quality of life in Parkinson patients especially in i nternational clinical trials.