(CBS NEWS) -- Measuring a particular blood protein might help doctors easily distinguish Parkinson’s disease from some similar disorders, a new study suggests.

The potential blood test is “not ready for prime time,” Parkinson’s disease experts said. But, it marks progress in the quest for an objective way to diagnose Parkinson’s and similar conditions known as atypical parkinsonian disorders, they noted.

Parkinson’s disease is a movement disorder that affects nearly 1 million people in the United States alone, according to the Parkinson’s Disease Foundation.

The root cause is unclear, but as the disease progresses, the brain loses cells that produce dopamine -- a chemical that regulates movement. As a result, people suffer symptoms such as tremors, stiff limbs, and balance and coordination problems that gradually worsen over time.

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