Health-related quality of life in Parkinson's disease: a study of outpatient clinic attenders.

OBJECTIVE: To assess the validity and responsiveness of a questionnaire to assess health-related quality of life in Parkinson's disease (PD)--the 39-item Parkinson's Disease Questionnaire (PDQ-39)--and to report problems experienced by patients by means of the questionnaire. METHODS: Patients completed the PDQ-39 and the SF-36 at baseline and 4 months later. At the same assessments, neurologists rated patients with Hoehn and Yahr and Columbia Scales. RESULTS: Evidence for validity of the new questionnaire was observed by agreement of scores with clinical scales at both assessments. Evidence for responsiveness of scales assessing physical function, particularly mobility and activities of daily living, was observed from significant paired t tests for differences between scores at baseline and follow-up, and correlations with patients' retrospective judgments and changes in the SF-36 summary scores. However, there were no significant associations with changes in neurologists' clinical scores. Patients most frequently reported problems of physical function in the PDQ-39. Scores for several dimensions of the PDQ-39 were significantly more favorable than those reported by nonclinic samples of patients with PD. CONCLUSIONS: The PDQ-39 has validity for use among patients attending neurological clinics for treatment of PD. There is also some evidence of responsiveness. The questionnaire identifies problems that are important to patients and that appear to be more commonly experienced by nonclinic attenders.