It may be possible to develop a simple blood test to diagnose multiple sclerosis, scientists believe.
Women are twice as likely to be affected by MS as men
MS is currently diagnosed through a combination of scans, tests and physical examination, and can be difficult to spot.
But researchers found people with relapsing-remitting MS have a distinct pattern of proteins in their blood.
The Wake Forest University study features in the Journal of Molecular Neuroscience.
MS is a progressive disease of the central nervous system that affects the brain and spinal cord.
Common signs can include fatigue, psychological changes, weakness or paralysis of limbs, numbness, vision problems, difficulties speaking or walking, bladder problems, and sexual dysfunction.
Eventually, patients may become totally paralysed and wheelchair-bound.
The Wake Forest team compared blood samples from 25 patients newly diagnosed with relapsing-remitting MS with samples from 25 healthy people.
Relapsing-remitting MS is the most common form of the disease, and is characterised by attacks interspersed with stable periods.
The researchers found that the MS patients had a different pattern of proteins - and their building blocks, peptides - in their blood.
Lead researcher Dr Jagannadha Avasarala said: "We found a distinct pattern in the MS group that revealed the existence of three markers for the disease.
"This suggests the potential for developing a blood test that could allow us to identify the earliest changes that represent MS and help in its diagnosis."
Dr Avasarala said there was probably not a single marker that could be used to detect MS.
Looking for patterns across a number of markers was probably a more effective strategy.
The researchers combined an analytical technique called combined mass spectrometry with sophisticated software designed to recognise protein patterns.
Christine Jones, of the MS Trust, said: "Obviously, this research is at an early stage but the prospect of a simple blood test to diagnose MS is extremely attractive.
"Currently, there is no one test that can diagnose MS and the process of identifying people with the condition can be long and stressful, often stretching over a period of months or even years.
"Many people with MS say that dealing with the uncertainty during diagnosis is harder than coping with any of the symptoms they ever experience.
"Clearly, a test that could provide a rapid and definitive diagnosis would enable those who do have MS to begin receiving treatment and support without delay and would also avoid unnecessary distress for those who are found not to be affected by the condition."
Mike O'Donovan, chief executive of the Multiple Sclerosis Society, said: "This interesting research is at an early stage and we look forward to seeing the results of the further analysis now under way."