More than skin deep: how the new Parkinson’s tests actually work

Richard Moore
Aug 12
9 min read

New tests can detect abnormal alpha-synuclein in skin and spinal fluid, sometimes before typical movement symptoms appear. Here is what they reveal, what they cannot predict, and where personalised nutritional support may fit.

A tremor. A slight drag in the walk. Fingers that no longer do exactly what they are told. These are usually the moments when Parkinson’s enters the conversation. By then the biological changes behind the condition may have been developing for years (Siderowf et al., 2023).

Scientists can now look for one of those early changes directly. A protein called alpha-synuclein, when it folds abnormally, leaves a trace that can be picked up in a small sample of skin or in cerebrospinal fluid, the clear liquid that cushions the brain and spinal cord (Coughlin et al., 2026).

For people living with Parkinson’s, or worrying that they might, this raises questions that feel very personal. Could the condition be identified before a tremor begins? If a test comes back positive, does that mean symptoms are inevitable? And what, if anything, can someone actually do with that information?

The answers are not as clear as most people hope. These tests give us a closer look at what is happening in the nervous system, but they cannot predict one person’s future, and they do not come with a list of foods and supplements to take (Coughlin et al., 2026).

When a helpful protein loses its shape

Alpha-synuclein is a normal protein found in nerve cells, particularly at the tiny junctions where one cell passes a message to another. It appears to help manage the release, storage, and recycling of chemical messengers (Sulzer & Edwards, 2019).

Like every protein, it has to fold into the right three-dimensional shape to work. The folds needed to make an origami bird are precise. Get one crease wrong and the whole thing collapses, and the misshapen pieces may start sticking together. In Parkinson’s disease and several related conditions, that is essentially what happens to alphasynuclein. It folds abnormally and begins to clump. These aggregates are a defining feature of Parkinson’s and dementia with Lewy bodies, though scientists are still working out which forms actually damage nerve cells and which are part of a broader process (Duggal & Kumar, 2024).

And the misfolded version does not stay put. It can act like a corrupted template, nudging normally folded protein to take on the same faulty shape. That copying behaviour is what gave scientists a new way to find it (Soto, 2024).

What a skin biopsy looks for

The skin biopsy test hunts for a specific altered form of alpha-synuclein within the tiny nerve fibres that run through skin. The form it is looking for, phosphorylated alpha-synuclein, has a phosphate chemical group attached to it in a way associated with pathological deposits (Gibbons et al., 2024)

After a local anaesthetic, a clinician takes several small, circular skin samples. In the laboratory, fluorescent antibodies are used to light up any abnormal deposits around the nerve fibres (Gibbons et al., 2024).

Results from a large 2024 study were striking. Phosphorylated alpha-synuclein was detected in 89 out of 96 participants with clinically diagnosed Parkinson’s disease, a rate of 92.7 per cent. It also showed up in people with multiple system atrophy, dementia with Lewy bodies, and pure autonomic failure. Four of the 120 control participants tested positive (Gibbons et al., 2024). A positive biopsy provides evidence of a synucleinopathy (the collective term for conditions involving abnormal alpha-synuclein), but it cannot by itself confirm a diagnosis of Parkinson’s disease, because several neurological conditions share this pathology. The study also used carefully selected participants and controls, and the researchers acknowledged that accuracy in everyday clinical practice may not match the figures they reported (Gibbons et al., 2024).

The amplification assay

The seed amplification assay works on the same protein but with a completely different logic.

Take one damaged document and put it through a photocopier set to reproduce the fault. Run enough copies and the damage is impossible to miss. The assay does something similar: a sample is mixed with normal alpha-synuclein, and if it contains any abnormal seeds, repeated cycles of shaking and resting coax them into recruiting the healthy protein and creating more aggregates. A fluorescent dye makes the growing signal visible. The result is reported as positive or negative for alpha-synuclein seeding activity (Concha-Marambio et al., 2023).

In the international Parkinson’s Progression Markers Initiative study, a cerebrospinal-fluid assay detected abnormal alpha-synuclein in 87.7 per cent of participants with Parkinson’s disease. Among people with typical sporadic Parkinson’s who also had a reduced sense of smell, sensitivity reached 98.6 per cent. Among healthy controls, 96.3 per cent received a negative result (Siderowf et al., 2023).

But the assay did not perform equally across all forms of the condition. Positivity was lower in some people carrying variants in the LRRK2 gene (leucine-rich repeat kinase 2), so a negative result cannot rule out every form of Parkinson’s (Siderowf et al., 2023).

Can the test find Parkinson’s before symptoms begin?

In some people at higher risk, abnormal alpha-synuclein can be detected before the movement symptoms required for a conventional diagnosis appear (Siderowf et al., 2023).

Researchers call this the prodromal stage. A reduced sense of smell and rapid eye movement sleep behaviour disorder are both associated with a higher likelihood of developing a synucleinopathy. In REM sleep behaviour disorder, the person physically acts out their dreams. In the Parkinson’s Progression Markers Initiative analysis, the assay was positive in 86 per cent of participants already classified as prodromal (Siderowf et al., 2023).

A 2026 study went a step further. Researchers looked at people with incidental Lewy body disease, where alpha-synuclein pathology was only discovered post-mortem in someone who had never received a clinical diagnosis during their lifetime. Abnormal seeding was found in 25 of 33 cerebrospinal-fluid samples, six of 16 skin samples, and 13 of 37 submandibular-gland samples (Adler et al., 2026). The skin sample numbers were small, so the figures are not a settled comparison. They support the possibility that abnormal alpha-synuclein can be detected before a clinical diagnosis.

What the test cannot do is tell an individual which further symptoms will develop, when they may appear, or how quickly the condition may change. There is also no established preventive treatment given solely on the basis of a positive assay in an otherwise healthy person (Coughlin et al., 2026). Testing before a diagnosis should always involve a specialist conversation about why the test is being considered and what either result would actually mean for that person.

Where the science is heading

Most seed amplification assays currently give a broadly yes-or-no answer. Researchers are now asking whether the speed and shape of the laboratory reaction might say more. In a 2025 study across 1,631 participants, faster reactions were associated with later cognitive decline in two Parkinson’s cohorts. The study was observational and the finding needs further validation, but it hints at a richer signal than a simple positive or negative (Orrú et al., 2025).

Blood-based assays are also being developed, with promising early results, though no standardised test is ready for general screening yet (Kong et al., 2026). Researchers have also proposed classification frameworks based on alpha-synuclein biology, dopamine-system changes, genetics, and symptoms. Their purpose is to identify suitable trial participants earlier and group them by shared biology, not to stage individual patients in the clinic (Höglinger et al., 2024; Simuni et al., 2024).

Where nutrition fits in

A positive alpha-synuclein test does not prescribe a diet. But it does raise a question worth sitting with: if changes may be building long before familiar movement symptoms appear, could supportive care begin earlier too?

At You Nutrition Clinic, the focus is not on treating a test result. It is on the person behind it: their digestive health, bowel function, appetite, weight, food quality, and how meals fit around medication. Parkinson’s affects far more than movement. Constipation, reduced appetite, swallowing difficulties, and unintended weight loss can all erode nutritional health quietly and persistently (Barichella et al., 2009; Mukherjee et al., 2016). Food can also affect how medication works. Levodopa and certain amino acids from dietary protein share the same transport system in the intestine and at the blood-brain barrier, and for some people a protein-rich meal delays or blunts levodopa’s effect. Adjusting the timing and distribution of protein may help with motor fluctuations, though this should never mean restricting protein without considering overall nutritional needs (Cereda et al., 2010; Virmani et al., 2016).

Research into the gut-brain axis is still developing, and gastrointestinal symptoms, constipation especially, can appear before or alongside movement symptoms. No diet has been shown to remove abnormal alpha-synuclein from the nervous system (Fasano et al., 2015; Coughlin et al., 2026). That needs to be said plainly, because it shapes what nutritional support can realistically offer.

Which is still quite a lot. Is the person eating enough? Has constipation become a daily problem? Do meals seem to be affecting medication? Is weight dropping? Have tremor or swallowing difficulties made cooking or eating harder? These are the questions that open up a useful conversation, one that turns concern into a practical plan based on this person’s symptoms, medication, and daily life, not a generic one.

Working with Melody

A diagnosis, unexplained symptoms, or a growing sense that something is wrong can all bring a flood of questions. Food is often one of the first places people look for some control, and that is a reasonable place to start. But general advice rarely fits an individual life.

Melody is You Nutrition Clinic's Parkinson's disease specialist as a registered nutritional therapy practitioner. She works with people experiencing symptoms, recently diagnosed, or at increased risk of Parkinsonism (the umbrella term for conditions causing slowness, stiffness, and tremor). Her focus brings together gastrointestinal health, the gut-brain axis, medication-aware nutrition, and practical day-to-day support.

To make an appointment with Melody or to find out more about the clinic's work across neurodegenerative conditions, visit younutritionclinic.com or contact her at melody@younutritionclinic.com

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Disclaimer: This article is for informational and educational purposes only and does not constitute medical advice. Always consult with a qualified, registered medical doctor (MD) for diagnosis and treatment decisions.

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