Tests
1st tests to order
dopaminergic agent trial
Test
The diagnosis of PD is made clinically, and in patients without atypical features no additional diagnostic testing is indicated.
If diagnostic testing is warranted due to atypical features or unclear clinical diagnosis, tests may include a dopaminergic agent trial.
Useful to confirm diagnosis.
In some instances, such as patients with tremor-predominant disease, doses as high as 1200 mg of levodopa may need to be reached before concluding lack of efficacy.
Result
improvement in symptoms
Tests to consider
MRI brain
Test
The diagnosis of PD is made clinically, and in patients without atypical features no additional diagnostic testing is indicated.
MRI should be ordered if atypical features (atypical course, early dementia, significant imbalance in early disease, autonomic dysfunction, gaze abnormalities, or atypical abnormalities on neurologic examination) are present.
Absence of dorsolateral nigral hyperintensity on 3.0 Tesla susceptibility-weighted scan (a normal finding, the "swallow-tail-sign") has been used to distinguish healthy controls from patients with neurodegenerative parkinsonism with high reliability.[90]
Assessment of dorsolateral nigral hyperintensity on iron-sensitive MRI may also be a marker of nigral pathology.[91]
Result
normal image in most patients with idiopathic PD; age-related changes such as mild small vessel disease acceptable; similarly acceptable if patient has appropriate history to explain other abnormalities (i.e., stroke, trauma); in advanced disease with dementia, may see cortical atrophy; dorsolateral nigral hyperintensity (the "swallow-tail-sign") may be absent
functional neuroimaging (dopamine transporter imaging such as FP-CIT or beta-CIT SPECT, or fluorodopa PET)
Test
The diagnosis of PD is made clinically, and in patients without atypical features no additional diagnostic testing is indicated.
If diagnostic testing is warranted due to atypical features or unclear clinical diagnosis, tests may include functional neuroimaging.
Functional neuroimaging may be helpful in distinguishing a neurodegenerative parkinsonian disorder from vascular, drug-induced, or psychogenic parkinsonism, or essential tremor, and also may serve as a preclinical marker for future application of neuroprotective agents.[76][77][78][79]
Result
decreased striatal presynaptic dopamine uptake
olfactory testing
Test
The diagnosis of PD is made clinically, and in patients without atypical features no additional diagnostic testing is indicated.
If diagnostic testing is warranted due to atypical features or unclear clinical diagnosis, tests may include olfactory testing.
Smell tests to support clinical diagnosis include the University of Pennsylvania Smell Identification Test (UPSIT) and the Sniffin' Sticks test.[73][74]
Result
hyposmia or anosmia
genetic testing
Test
The diagnosis of PD is made clinically, and in patients without atypical features no additional diagnostic testing is indicated.
If diagnostic testing is warranted due to atypical features or unclear clinical diagnosis, tests may include genetic testing.
Should be performed if young-onset disease or a significant family history exists, with the assistance of a movement disorders specialist and a genetic counselor. Often done as part of a research protocol to determine or investigate a particular lineage, and rarely used as a primary means to establish a diagnosis.[84]
Result
specific mutation would be identified
neuropsychometric testing
Test
The diagnosis of PD is made clinically, and in patients without atypical features no additional diagnostic testing is indicated.
If diagnostic testing is warranted due to atypical features or unclear clinical diagnosis, tests may include neuropsychometric testing.
Performed if cognitive deficits are reported in history or demonstrated in bedside screening.
Result
executive dysfunction can occur in PD with dementia
serum ceruloplasmin
Test
The diagnosis of PD is made clinically, and in patients without atypical features no additional diagnostic testing is indicated.
If diagnostic testing is warranted due to atypical features or unclear clinical diagnosis, tests may include serum ceruloplasmin.
In all younger patients (<40 years), a diagnosis of Wilson disease should be excluded. The presence of Kayser-Fleischer rings on slit-lamp exam supports this diagnosis.
Result
low in Wilson disease
24-hour urine copper
Test
The diagnosis of PD is made clinically, and in patients without atypical features no additional diagnostic testing is indicated.
If diagnostic testing is warranted due to atypical features or unclear clinical diagnosis, tests may include 24-hour urine copper.
In all younger patients (<40 years), a diagnosis of Wilson disease should be excluded. The presence of Kayser-Fleischer rings on slit-lamp exam supports this diagnosis.
Result
elevated in Wilson disease
cardiac sympathetic innervation using iodine-123 meta-iodobenzylguanidine (MIBG)
Test
May be used to distinguish PD from other neurodegenerative parkinsonian syndromes. MIBG uptake by postganglionic cardiac sympathetic neurons is grossly reduced at an early stage of PD in almost all patients with a clinical severity score of Hoehn and Yahr II or higher.[67][80][81][82]
Result
decreased heart-to-mediastinum average count ratio in PD; normal in multiple system atrophy
brain pathology (postmortem)
Test
Impractical to perform on patient antemortem (except in extraordinary circumstances).
Gross examination may reveal frontal atrophy and loss of pigmented cells of substantia nigra; microscopic observation of presence of Lewy bodies and positive reactivity to synuclein with immunohistochemical staining.
Result
nigrostriatal degeneration and Lewy bodies
Emerging tests
skin biopsy
Test
Abnormal dermal alpha-synuclein aggregates have been shown to be similar to midbrain alpha-synuclein in patients with PD; therefore, abnormal dermal alpha-synuclein may be a suitable surrogate for central nervous system (CNS) pathology. Dermal phosphorylated synuclein is found mainly in autonomic nerve terminals, richly innervating dermal autonomic annexes (blood vessels, pilomotor muscles, and sweat glands).[85][86]
Result
abnormal dermal alpha-synuclein aggregates in patients with PD
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