Cross-cultural evaluation of the Parkinson's Disease Questionnaire: tests of data quality, score reliability, response rate, and scaling assumptions in the United States, Canada, Japan, Italy, and Spain.

BACKGROUND AND OBJECTIVES: Health status measures, used to measure the subjective functioning and well-being of respondents, are increasingly being used in trials of treatments that are undertaken in a variety of countries. To assess comparability of results gained from such cross-cultural studies, it is important for researchers to know the comparability of instruments across cultures. One measure widely used in cross-cultural studies is the Parkinson's Disease Questionnaire (PDQ-39). We evaluated response rate, data quality, score reliability, and scaling assumptions of the instrument in the United States, Canada, Spain, Italy, and Japan. METHODS: Our data were gained from the Global Parkinson's Disease Survey, a cross-national survey, in which the PDQ-39 was interviewer administered to respondents. RESULTS: Our data suggest that the PDQ-39 is, for the most part, a valid and reliable measure that can be appropriately and meaningfully used in cross-cultural studies. However, one of the dimensions of the measure, Social Support, may not be sufficiently reliable to be used as a primary endpoint in trials. CONCLUSION: The PDQ-39 seems to be sufficiently robust to be used in trials and surveys in cross-cultural studies.