International use of health status questionnaires in Parkinson's disease: translation is not enough.
The present study assessed the linguistic and content validity of the Swedish version of the 39-item Parkinson's disease questionnaire (PDQ-39). The frame question, response alternatives and two of the 39 items yielded substantial linguistic and stylistic problems. Such shortcomings would be expected to influence responses to, and the quality of, the whole questionnaire. Data support content valid