An experimental blood test that detected Parkinson’s disease in a preliminary study could become the first specific tool for diagnosing the devastating neurodegenerative condition, according to researchers.

The test, which looks for cell damage associated with the disease, is years away from being commercially available. If its reliability is confirmed in future trials, the test would allow doctors to diagnose the condition earlier and start therapies sooner, before nervous system damage worsens, the researchers said.

“Currently, Parkinson’s disease is diagnosed largely based on symptoms, when patients already have significant neurological damage,” said study leader Laurie Sanders of Duke School of Medicine in Durham, North Carolina.

The new blood test measures DNA damage in mitochondria, the structures inside cells that generate energy for cellular functions. Mitochondrial DNA damage is known to be associated with Parkinson's disease.

The test showed greater damage in blood cells from patients with Parkinson’s compared to people without the disease, researchers reported in Science Translational Medicine.

It also found elevated DNA damage in people with a genetic mutation called LRRK2 that increases the risk for Parkinson’s disease, even in the absence of symptoms, they said.

Presently, drugs for Parkinson’s disease only help control symptoms. Sanders said she hopes that along with diagnosing Parkinson’s, the new test will help identify drugs that can reverse or halt mitochondrial DNA damage and the disease process, as well as patients who could benefit from those drugs.

Several companies including Abcam and Biogen with partner Denali Therapeutics are testing such experimental treatments.

"A new blood-based diagnostic test would be a major advancement for Parkinson’s disease, which afflicts 10 million people worldwide and is the second most common neurodegenerative disease after Alzheimer's," the researchers said.

Going forward, the researchers plan to test the diagnostic in samples from high-risk individuals who have not yet developed symptoms.