Tests Show Promise for Diagnosing Parkinson's and Dementia with Lewy Bodies

Diagnosing Parkinson's disease (PD) and dementia with Lewy bodies (DLB) remains a challenge. There is no single definitive test, and misdiagnosis can lead to ineffective treatments. That is why finding reliable biomarkers — measurable signs in the body that can indicate disease — is a major focus of PD research today. Biomarkers hold the promise of earlier, more accurate diagnosis, tracking disease progression and evaluating whether treatments are working.

PD and dementia with Lewy bodies are both Lewy body disorders. They both lead to the abnormal buildup of a misfolded protein called alpha-synuclein and the loss of dopamine. A protein called DDC plays a role in producing dopamine, so in Lewy body disorders such as PD, DDC levels change — making it a potentially useful signal (or biomarker) that the disease is present.

A new study published in Nature Medicine — featuring former Parkinson's Foundation awardee Giovanni Bellomo, PhD — highlights DDC as a promising new biomarker. Using cerebrospinal fluid collected through a spinal tap, the research team developed new tests to measure DDC levels and confirmed their accuracy across more than 1,100 people.

This study adds to a growing wave of biomarker discoveries that are transforming how we understand and diagnose PD. Last year, a study showed that a skin biopsy test could reliably detect phosphorylated alpha-synuclein (another potential biomarker) in people with PD and related disorders, which is now commercially available to help support diagnosis.

Together, these advances are moving us closer to an era where biological tests might offer earlier and more precise diagnosis.

Study Results

The researchers developed two new tests to measure DDC levels in cerebrospinal fluid and then confirmed their accuracy across more than 1,100 people. This included people with PD, dementia with Lewy bodies, Alzheimer’s disease and people without these conditions.

Overall, DDC levels in spinal fluid were significantly and consistently higher in people with PD and dementia with Lewy bodies — up to 2.5 times higher compared to people without these diseases and nearly twice as high as those with Alzheimer’s disease. The test accurately distinguished PD and dementia with Lewy bodies with 94% to 97% accuracy. It also differentiated these conditions from Alzheimer's disease.

Interestingly, people with Parkinson’s movement symptoms had higher DDC levels, but those levels didn’t increase as symptoms worsened. This suggests DDC may be most helpful for confirming a diagnosis rather than tracking disease progression.

In brain tissue examined after death, higher DDC levels measured during life matched up with greater buildup of alpha-synuclein — the hallmark protein involved in PD and DLB — reinforcing DDC’s connection to the underlying biology of these diseases.

Highlights

• A new test uses the protein called DDC as a biomarker to help identify PD with the hope that it could be a diagnostic tool one day.

• DDC levels in spinal fluid were significantly higher in people with PD and dementia with Lewy bodies —up to 2.5 times higher than in people without these diseases and nearly twice as high as in those with Alzheimer’s disease.

• Overall, the tests were accurate at distinguishing PD and dementia with Lewy bodies from people without these diseases and reliably differentiated these conditions from Alzheimer’s disease. These results suggest these tests could eventually be useful diagnostic tools for doctors. 

• People with symptoms (for example, movement problems in PD) had higher DDC levels. However, DDC levels didn't increase as symptoms got worse.

• In brain tissue examined after death, higher DDC levels measured during life matched up with greater buildup of alpha-synuclein.

What Does This Mean?

This research points to a potential new biomarker — a protein called DDC — that may help diagnose Parkinson’s and dementia with Lewy bodies (DLB) more accurately and earlier than current methods.

The DDC test showed high accuracy in distinguishing PD or DLB versus people without these conditions, as well as compared to people with Alzheimer’s disease. This accuracy is crucial for a neurological diagnostic test, especially for conditions where misdiagnosis is common due to overlapping symptoms and a lack of established biomarkers.

In the near future, this could help people be diagnosed with Parkinson’s and DLB more accurately and faster, which can dramatically improve treatment outcomes. However, in its current form, the results of this study suggest that the DDC biomarker may be best for confirming a diagnosis, but less helpful for tracking how the disease develops.

What Do These Findings Mean for People with Parkinson’s Right Now?

The DDC biomarker is not yet available as a clinical test. However, as we saw with the skin biopsy test (Syn-One), biomarker advances can quickly move from a research study to being used in-clinic. Additionally, considering that very few tests are 100% accurate, the concept of having multiple different biomarkers available to identify PD will help validate diagnoses and improve rigor in the field.

Studies like this one could help bring peace of mind to people with Parkinson’s and support diagnosis based on biological evidence, not only a doctor’s assessment.

For people with Parkinson’s, this study reinforces that the symptoms they experience reflect measurable brain changes in the brain. People who are concerned that they might have Parkinson’s disease or dementia with Lewy bodies should talk to their doctor.

Learn More

The Parkinson’s Foundation believes in empowering the Parkinson’s community through education. Learn more about PD and sleep through our resources below, or by calling our free Helpline at 1-800-4PD-INFO (1-800-473-4636) for answers to your Parkinson’s questions.

• Understanding Parkinson’s Biomarkers

• A Skin Test Could Detect Parkinson’s and Related Diseases

• Lewy What? Explaining Lewy Body Dementia

• Lewy Body Dementia Association