By Joi Preciphs, Bloomberg News

Scientists identified a pattern of abnormal functioning in 22 genes that might someday be used in a test to spot people most at risk for Parkinson’s disease.

The so-called molecular marker was associated with the disease in a study published today in the Proceedings of the National Academy of the Sciences. Among the 105 patients studied, those with the highest marker scores had a fivefold risk of developing the disease, the researchers reported.

No laboratory test exists to diagnose the neurological disorder, characterized by tremors and other woes that worsen over time. Researchers are trying to isolate biological markers that would allow for trials of drugs to prevent the condition or delay its onset, while possibly also enabling earlier diagnoses. “We’re really here at the beginning of the beginnings of a blood test for Parkinson’s disease,” the lead author of the study, Clemens Scherzer, an associate neurologist at Brigham and Women’s Hospital, a teaching venue for Harvard Medical School in Boston, said today in a telephone interview. “It gives us great hope and is an important breakthrough.”

Scherzer and colleagues constructed a risk marker for the disorder from scanning the total genome-wide expression changes in the blood of earlystage Parkinson’s patients. The screen also identified genes that were transcribed differently in Parkinson’s patients, compared with control groups, according to the report.

The majority of Parkinson’s patients are diagnosed at the stage at which unmistakable symptoms are present. By then, nearly 70 percent of the cells that produce dopamine, a chemical messenger, in the brain’s substantia nigra region have already malfunctioned. Dopamine helps transfer signals to parts of the brain that control movement and coordination. “You’re really too late,” Scherzer said. “The horse is out of the barn.”

Parkinson’s afflicts about 2 of every 1,000 people and most often develops after age 50, according to the Web site of the U.S. National Institutes of Health. Each year, about 40,000 people are diagnosed with the disease, says the Parkinson’s Disease Foundation, a New York-based advocacy and research organization.

Scherzer said he envisions a situation in which primary-care physicians could order a screen for patients experiencing nonspecific movement changes that may indicate disease. Doctors could categorize and better assess patients’ needs. High-risk patients could be sent immediately to a movement-disorder specialist for treatment.

Larger cross-sectional studies at multiple test sites are needed to confirm the results before a genetic test reaches doctors’ offices. A prospective study evaluating pre-symptomatic patients for a few years is also needed, Scherzer said.

The study released today was financed by the Michael J. Fox Foundation for Parkinson’s Research. The Canadian-born actor Michael J. Fox, who has the disease, established the New York- based foundation in 2000.