Few people with Parkinson’s have an uncomplicated journey to diagnosis. One study found that clinical misdiagnosis occurs as often as 30% of the time. Diagnosis is especially difficult when your symptoms are mild; importantly, symptoms may evolve over time, so some people receive an initial diagnosis that changes months or years later. Diagnostic tests may be helpful in supporting a clinical diagnosis, upon initial evaluation or as symptoms evolve.
Your healthcare provider may order certain tests—including MRI or lab tests—upon your first visit. These tests help evaluate for structural or metabolic conditions but do not support a diagnosis of Parkinson’s specifically.
- A clinical assessment of an individual’s response to levodopa can be helpful to clinicians in assessing for the possibility of Parkinson’s.
- DaTscan is utilized as a nuclear imaging-based study that can help with diagnosis.
- Genetic testing provides some information about potential genetic risk factors for Parkinson’s.
- Tissue and fluid-based biomarkers have been the focus of many news articles relating to the diagnosis of Parkinson’s. The Syn-One Test® was initially launched in 2019, and the SYNTap® Test has been available since 2021. These newer diagnostic aids can improve confidence in a clinical diagnosis of Parkinson’s.
How Parkinson’s is Diagnosed
An official Parkinson’s diagnosis requires a healthcare provider to clinically evaluate the symptoms they observe. This is difficult for multiple reasons, including variability of symptoms and because many Parkinson’s symptoms are similar to symptoms of other conditions.
- Parkinsonism—specifically bradykinesia, plus either tremor or rigidity or both
- At least two supportive findings
- Lack of exclusion criteria that suggest an alternative diagnosis
Supportive findings include:
- Beneficial response to levodopa
- Levodopa-induced dyskinesia
- Rest tremor
- Loss of sense of smell
- REM sleep behavior disorder (RBD)
Some experts believe the only way to confirm a Parkinson’s diagnosis is to discover specific neuropathological signs during an autopsy. (Certainly, this is less than ideal for those who are alive and well and desperately want to understand what’s going on.) Relevant signs at autopsy include degeneration in a part of the brain called the substantia nigra, and misfolded alpha-synuclein, a common protein.
How Tissue and Fluid-Based Tests Improve Diagnostic Accuracy
Because Parkinson’s is thought to involve misfolded alpha-synuclein, it is sometimes called a synucleinopathy. Tests that examine skin and cerebrospinal fluid samples can indicate abnormally shaped alpha-synuclein.
Detection of misfolded alpha-synuclein with the help of these tests increases the likelihood that your symptoms are caused by a synucleinopathy. Since not all conditions that look like Parkinson’s involve alpha-synuclein, these new tests help narrow the list of likely diagnoses to explain your symptoms.
This is a major development in Parkinson’s research. In addition to improving healthcare providers’ confidence in diagnoses, these tests allow researchers to more effectively select participants for clinical trials. In the future, the tests may also provide ways to evaluate effective treatments and track progression of Parkinson’s. There are already indications that the technology may be able to differentiate between Parkinson’s and other conditions involving misfolded alpha-synuclein. Critically, these tests detect abnormal alpha-synuclein when symptoms are mild or otherwise difficult to differentiate.
The Syn-One Test, developed by CND Life Sciences, highlights misfolded alpha-synuclein in a skin biopsy and identifies pathological alpha-synuclein associated with Parkinson’s, dementia with Lewy bodies (DLB), multiple system atrophy (MSA), REM sleep behavior disorder, and pure autonomic failure. Healthcare providers can use this test in combination with clinical exams to make a more accurate diagnosis.
CND Life Sciences reports that in a study of 428 people, the Syn-One Test was found to detect misfolded alpha-synuclein in people living with the conditions listed above with 96% accuracy.
According to Principal Investigator of the study and Chief Medical Officer at CND Life Sciences Todd Levine, MD, “We also continue to publish encouraging findings that the Syn-One Test can reveal distinct 'synuclein signatures' in the skin that may help us differentiate among the synucleinopathies, including Parkinson’s vs MSA vs DLB.” For example, there is early evidence that the Syn-One Test can differentiate between alpha-synuclein deposition patterns associated with MSA and with typical Parkinson’s however, the test is not yet validated for that purpose.
CND Life Sciences is a Medicare and Tricare participating provider and is working to establish in-network contracts with commercial payers given its strong and increasing body of scientific and clinical utility evidence. Since health benefits vary with different programs and plans, CND’s Patient Access team can help determine your expected benefits coverage before you schedule the required skin biopsies for the Syn-One Test. CND also offers self-pay options and payment plans as needed.
The SYNTap Test, developed by Amprion, highlights misfolded alpha-synuclein in spinal fluid. This test can identify alpha-synuclein associated with Parkinson’s, Lewy body dementia, Alzheimer’s with Lewy bodies, MSA, and mild cognitive impairment with Lewy bodies.
As with the Syn-One Test, the SYNTap Test may be able to differentiate between MSA and Parkinson’s. One study found that SYNTap Test can differentiate between Parkinson’s and MSA over 95% of the time.
The SYNTap Test has received breakthrough device designation from the FDA for people being evaluated for a Parkinson’s diagnosis. The test is not presently covered by insurance.
How Older Tests Remain Helpful
Older diagnostic tests can still provide information to healthcare providers in evaluating your symptoms and forming a diagnosis.
With an MRI, a provider looks for structural issues to explain your symptoms. A provider may order a blood test to look for abnormal levels of hormones, nutritional deficiencies, or evidence of other systemic issues.
A levodopa challenge test is when you take levodopa and see if it helps alleviate your symptoms. If you have a clear benefit which persists over a period of many months, this suggests a Parkinson’s diagnosis. If your response to levodopa is poor, inconsistent, or worsens over a brief period, this is evidence that another condition may be causing your symptoms.
Genetic testing can also be helpful. Certain genetic variants are known to cause Parkinson’s, and if you have one of these variants and meet the clinical criteria above, this supports a Parkinson’s diagnosis. There are also variants known to increase risk and having one or more of these variants supports a Parkinson’s diagnosis. The PDGeneration study allows you access to free genetic testing for some common genetic variants.
For many years, the DaTscan has been the most ordered test to help establish a Parkinson’s diagnosis. A DaTscan involves using a radioactive chemical that binds to the dopamine transporter and evaluates levels of dopamine in your brain. Parkinson’s is known to feature a particular pattern of dopamine transporter activity, and when that pattern appears in DaTscan results, the scan is compatible with a diagnosis of Parkinson’s.
Determining Which Tests are Right for You
Consult your medical care team to determine which tests are right for you. Even the tests covered by insurance may have high copays, and each test has limitations. Given the potential costs, it is important that you understand what information your test results will be able to provide and how useful that information will be for you.
It is also important to understand what is involved in the procedures before you schedule them. Some tests are more complicated than others. For example:
- The Syn-One Test is a simple, 15-minute outpatient procedure that requires a local anesthetic.
- MRI and DaTscan exams can be uncomfortable because they require you to be still, which can be difficult for many people living with symptoms of Parkinson’s.
- A DatScan also involves an injection of a radioactive chemical, and, although the level of radiation is extremely low and is considered safe, this may be off-putting.
- The results of genetic testing can have implications for family members.
- The SYNTap Test requires a lumbar puncture.
As technology and research progresses, tests may become more valuable and informative. Especially with the development of newer tests that detect abnormal alpha-synuclein, there are now more tools than ever to make a Parkinson’s diagnosis more quickly, confidently, and with less fuss, such as giving a few minor skin samples in your doctor’s office.
This post was written by the Davis Phinney Foundation.
This post is sponsored by CND Life Sciences.