Accuracy of diagnosis in patients with presumed Parkinson's disease.

OBJECTIVES to study the diagnostic accuracy for parkinsonism and Parkinson's disease in a community-based sample of subjects on anti-parkinsonian medication. METHODS computerized prescribing records in general practice were used to create a community-based disease register for Parkinson's disease. Subjects were examined to establish the likely diagnosis using recommended clinical diagnostic criteria. RESULTS of 402 cases, parkinsonism was confirmed in 74% and clinically probable Parkinson's disease in 53%. The commonest causes of misdiagnosis were essential tremor, Alzheimer's disease and vascular pseudo-parkinsonism. Over one-quarter of subjects did not benefit from anti-parkinsonian medication. CONCLUSIONS there is difficulty in diagnosing parkinsonism and Parkinson's disease in elderly subjects and we suggest early referral of those suspected of having parkinsonism for specialist assessment.