Measuring symptom change in patients with Parkinson's disease.

BACKGROUND The 39-item Parkinson's disease questionnaire (PDQ-39) is more sensitive to functional change than other measures of health and disability. AIM To determine the ability of this scale to change over time and the concurrent validity of some of its subscales. METHODS We assessed a cohort of 67 Parkinson's patients for 18 months, using the PDQ-39, the GHQ-28 general health questionnaire and the Office of Population and Census Surveys disability instrument. RESULTS The Office of Population and Census Surveys disability instrument and GHQ-28 recorded no significant change, but the PDQ-39 showed marked changes in levels of functioning. We also analysed changes on the PDQ-39 subscales as well as concurrent validity data for several subscales. This showed concurrent validity with the Beck depression and anxiety inventories, the Barthel index and the Royal Postgraduate Medical School severity scale. There was a high level of concurrent validity for all comparisons except for the Barthel index. CONCLUSION The PDQ-39 is a sensitive tool for monitoring change in patients with Parkinson's disease. It has high levels of concurrent validity with established measures of mood and motor function.