Researchers Develop Skin Test With Potential to Diagnose Parkinson’s Disease

Nurse with older patient.

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Key Takeaways

  • A skin test developed by researchers at Iowa State University shows promise in rapidly and accurately diagnosing Parkinson’s disease.
  • It works by identifying the presence of misfolded apha-synuclein proteins, a telltale sign of Parkinson’s. 
  • Early-stage Parkinson’s disease can be difficult to diagnose because its symptoms often mimic those of other diseases and disorders or are attributed to aging. 

Parkinson’s disease (PD) is infamously difficult to diagnose, so much so that only an autopsy can serve as definitive proof of its presence in the brain. Research suggests, however, that a cadre of scientists may have cracked the code.

Led by Anumantha Kanthasamy, MS, MPhil, PhD, distinguished professor of biomedical sciences at Iowa State, the scientists developed a simple skin test that appears to be able to diagnose Parkinson’s and similarly presenting diseases, collectively known as “parkinsonism,” with a high level of accuracy. The September study was published in the journal Movement Disorders.

Some challenges remain, but overall, Kanthasamy tells Verywell, “I think what we made is a huge leap in terms of grabbing some peripheral biomarkers for parkinsonism, including Parkinson’s disease.” 

Parkinson’s disease is characterized by hand tremors; bradykinesia, or limb rigidity; and impairments in balance and coordination. It commonly appears around the age of 60, although 5% to 10% of patients have what has become known as “early-onset disease,” meaning their symptoms began before they turned 50. In addition to middle or old age, a family history of Parkinson’s is another major risk factor for the movement disorder. 

Testing Skin

With the tongue-twisting technical name of “real-time quaking-induced conversion assay,” the test, known as “RT-QuIC” for short, has strange origins. It was originally developed to diagnose mad cow disease—a fatal neurodegenerative disorder caused by infectious agents called prions that affects adult cattle and, in rare cases, can be transmitted to humans. The team of researchers tweaked the clinical technology to be able to detect not only prions but also misfolded alpha-synuclein proteins—Parkinson’s disease’s biological signature.

“Alpha-synuclein clumping is the defining feature of PD,” Svjetlana Miocinovic, MD, PhD, assistant professor in the department of neurology at Emory University School of Medicine in Georgia, tells Verywell. “Parkinson’s disease is definitively diagnosed only on autopsy when alpha-synuclein clumps are observed in the brain. We don't know what causes alpha-synuclein to clump, but when it does, it leads to neuronal dysfunction and death, eventually leading to signs and symptoms of Parkinson’s disease.”

Critically, however, two of the study’s authors—Thomas Beach, MD, PhD, head of the Civin Laboratory at Banner Sun Health Research Institute in Arizona, and Charles Adler, MD, PhD, professor of neurology at Mayo Clinic Arizona—found that these protein clumps accumulate in other body tissues as well as the brain, including the skin. With this knowledge, they conducted RT-QuIC tests on 50 skin samples, half of which had been taken from people with Parkinson’s. The test identified protein clumping in 24 out of the 25 people with Parkinson’s and only one out of 25 of the people without Parkinson's—an encouraging 96% success rate, even considering the small sample size. 

“These results indicate tremendously high sensitivity and specificity, which is critical for a diagnostic test,” Adler said in a Newswise piece. Consequently, Kanthasay said, “We think there will be a lot of interest in the potential use of skin samples for diagnosis.” 

While the study involved skin samples from people who had late-stage Parkinson’s, Kanthamany is confident that it will shortly be applicable to people who have early-stage Parkinson’s as well.

Although “we need a larger sample size,” he says, “we have some evidence to show that [the assay] can detect early stages.” 

While Mocinovic sees a lot of potential in the skin test, she adds a word of caution. 

"[It's] also important to consider that there are several other diseases that feature alpha-synuclein clumps (in different distribution than Parkinson’s disease) such as Lewy body dementia and multi-system atrophy,” she says. “So any test that detects AS should ideally be able to distinguish between Parkinson’s disease and these Parkinson’s disease-like disorders.”

David K. Simon, MD, PhD, professor of neurology at Harvard Medical School, agrees that the first order of business is to refine the skin test enough that it can tell the difference between Parkinson’s and types of parkinsonism such as PSP and MSA.

This is “especially relevant for MSA because that's also a-synuclein apathy,” he tells Verywell, meaning that MSA is also characterized by alpha-synuclein protein clumping. 

Kanthamany says the test does not yet have a way to differentiate between these neurodegenerative disorders. But he is optimistic that he and his team will be able to develop one. 

“I think our goal is to, in the next batch of studies that we're thinking of, [determine], ‘Is there any difference in the amount of aggregated alpha-synuclein in this different subpopulation of disease?’” Kanthamany says. “‘Is there any difference in how that matches with the imaging data, a few other clinical observations?’ We are in the process of doing that work.” 

What This Means For You

This skin test could potentially diagnose Parkinson's disease earlier and more accurately. However, more testing needs to be done before the skin test is approved and made widely available.

The Problem of Missed Diagnosis or Misdiagnosis

If widely circulated, this skin test could potentially cause a spike in the number of successful diagnoses made every year. 

“Parkinson’s disease is not straightforward to diagnose because diagnosis is based on clinical evaluation, meaning the patient history and physical exam,” Miocinovic says. “So one has to suspect Parkinson’s disease in order to ask the right questions and test for specific disease signs. And early on, symptoms may not clearly point to Parkinson’s disease.”

Many early symptoms of Parkinson’s are dismissed as byproducts of the aging process. In some cases, they are even attributed to another epidemiological cause entirely. Some of these symptoms include:

  • Constipation
  • Incontinence
  • Restless leg syndrome
  • Reduced sense of smell

“Sometimes other disorders early on can mimic Parkinson's, with a couple of the disorders that commonly are mistaken for Parkinson's being progressive supranuclear palsy, or PSP, or multiple system atrophy, or MSA, because sometimes early in the course, they can look very similar to Parkinson's,” Simon says. “Even movement disorder specialists who think it's Parkinson's early in the course aren't right as often as we'd like to think we are.” 

This wide margin of error has immense ramifications for the work of the neuroscientists who study the disease in the hope of developing successful treatments. 

“The clinical diagnostic accuracy for early-stage Parkinson’s disease has been quite poor, only around 50-70%,” Beach tells Newswise article. “And since clinical trials really need to be done at an early stage to avoid further brain damage, they have been critically hampered because they have been including large percentages of people who may not actually have the disease.”

In other words, it’s difficult, nigh impossible, to know whether a drug works as expected when a significant number of the people taking it might not actually have the disease the drug was designed to treat. By providing more accurate diagnoses, a “better diagnostic test would help us develop these disease-modifying therapies by enrolling appropriate patients into clinical trials,” Miocinovic says. 

There is currently no cure for Parkinson’s, although medications, surgical procedures, and physical, occupational, and speech therapies, are available to treat it.

3 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Manne, S., Kondru, N., Jin, H., Serrano, G.E., Anantharam, V., Kanthasamy, A., Adler, C.H., Beach, T.G. and Kanthasamy, A.G. Blinded RT‐QuIC analysis of α‐Synuclein biomarker in skin tissue from Parkinson's disease patients. Mov Disord. 2020. doi:10.1002/mds.28242

  2. National Institutes on Aging. Parkinson’s disease.

  3. U.S. Food and Drug Administration. All about BSE (mad cow disease).

By Caroline Tien
Caroline Tien is a journalist with degrees in English and biology. She has previously written for publications including Insider and Cancer Health.