Scientists have developed a blood test that appears to be the first reliable way to predict whether patients with neurological problems such as tingling or blurred vision will soon develop the debilitating disease multiple sclerosis.

Austrian researchers studying patients with possible MS symptoms found that those with two kinds of antibodies in their blood early on were 76 times more likely to develop the tough-to-diagnose disorder than those with neither antibody.

Some of the potential early symptoms of MS can have numerous other causes, such as a stroke or a brain tumor. Moreover, one-third of patients with these initial symptoms recover and never develop MS. Others can go for years before they have a second flare-up showing they have MS.

Up to now, "nobody was able to predict for an individual patient what will be in the future," said lead researcher Thomas Berger of the department of neurology at the University of Innsbruck.

MS is incurable. Berger said the blood test could help doctors decide whether to offer a patient early treatment with drugs recently proven to reduce flare-ups and slow the progression of the disease in some people.

The best current diagnostic test, an MRI scan for lesions on nerves in the brain and spinal cord, can only predict the chances of developing multiple sclerosis over the next decade, and its accuracy ranges from 80 percent to 11 percent, Berger said. The blood test is 95 percent accurate in predicting which people will have a flare-up within several months, he said.

"These antibodies seem to predict the next attack and therefore a diagnosis of MS," said Stuart Cook, a neurologist and president of the University of Medicine and Dentistry of New Jersey. "I think it's an important contribution."

About 400,000 Americans, mostly women, have multiple sclerosis, which usually strikes between age 20 and 40.

MS is poorly understood but involves damage to nerve fibers and their protective myelin sheath in the brain, spinal cord and eyes. The cause is unknown, but doctors suspect a virus or other infection makes the immune system attack the myelin and nerve fibers.

Symptoms include weakness, tremors, difficulty walking, blindness, incontinence and emotional problems.

The disease can lie dormant for months or years, then worsen steadily or cause repeated flare-ups. Some victims become disabled, but others lead fairly normal lives.

Often, MS is not diagnosed until the second episode of symptoms. Many doctors just monitor patients until then, rather than starting treatment, because the initial symptoms often are not due to MS at all; because medications do not work for some people and have serious side effects; and because MRIs, even when combined with spinal fluid tests and patient history, can be inaccurate.

In the Austrian study, reported in today's New England Journal of Medicine, doctors tested 103 patients with possible early symptoms for their levels of antibodies called anti-MOG and anti-MBP. MRI scans were used to determine how many nerve lesions they had.

In an accompanying editorial, Jack P. Antel and Amit Bar-Or of the Montreal Neurological Institute said the findings, once confirmed, could identify subgroups of patients that particular drugs would help the most. Choosing the right drug now is hit-or-miss.