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.