Differential diagnosis

The diagnosis of PD is largely determined by medical history, clinical examination, and response to treatment; there is currently no reliable biochemical, imaging or genetic test that provides a definitive diagnosis.^5,6 However, laboratory tests are used in differential diagnosis of other health problems.⁷

Clinicians tend to diagnose PD incorrectly in approximately 25% of cases,¹ although some evidence suggests that this figure has fallen over time, and that diagnostic accuracy is improving, and in some instances can be very good indeed.^3,4 A correct diagnosis of PD may be delayed as many of the symptoms could, at first, be confused with the normal process of ageing, or other comorbidities.⁷ Even when motor symptoms appear, an erroneous diagnosis of Alzheimer’s disease, dementia with Lewy bodies (DLB), or drug-induced parkinsonism might easily be made.¹

DLB has similar clinical and neuropathological features to PD, but may be distinguished by the presence of cognitive impairment and hallucinations (unrelated to therapy) early during the disease process.⁸ There are many other conditions that present with symptoms similar to those of PD, and patients may therefore require expert evaluation to confirm a diagnosis.⁷

References:
1.Tolosa E, Wenning G, Poewe W. The diagnosis of Parkinson’s disease. Lancet Neurol 2006; 5 (1): 75–86.

2.Höglinger GU, Adler CH, Berg D, et al. A biological classification of Parkinson’s disease: the SynNeurGe research diagnostic criteria. Lancet Neurol 2024; 23 (2): 191–204.

3.Postuma RB, Lang AE. The clinical diagnosis of Parkinson’s disease – we are getting better. Mov Disord 2023; 38 (4): 515–517.

4.Virameteekul S, Revesz T, Jaunmuktane Z, et al. Clinical diagnostic accuracy of Parkinson’s disease: where do we stand? Mov Disord 2023; 38 (4): 558–566.

5.Jankovic J. Parkinson’s disease: clinical features and diagnosis. J Neurol Neurosurg Psychiatry 2008; 79: 368–376.

6.Williams DR, Litvan I. Parkinsonian syndromes. Continuum (Minneap Minn) 2013; 19 (5): 1189–1212.

7.DeMaagd G, Philip A. Parkinson’s disease and its management. Pharmacol Therapeut 2015; 40 (8): 504–510.

8.Litvan I, MacIntyre A, Goetz CG, et al. Accuracy of the clinical diagnoses of Lewy body disease, Parkinson disease, and dementia with Lewy bodies: a clinicopathologic study. Arch Neurol 1998; 55 (7): 969–978.