Scientists are closing in on a blood test for fibromyalgia, and the result could save patients from what is currently a lengthy and vague process of diagnosis.

Researchers at Ohio State University are now aiming to have a diagnostic blood test available for widespread use within the next five years.

Their confidence stems from a recently discovered biomarker - a "metabolic fingerprint" as the researchers put it - traceable in the blood of those with the disorder.

"We found clear, reproducible metabolic patterns in the blood of dozens of patients with fibromyalgia," says lead author Kevin Hackshaw, a rheumatologist at Ohio State University.

"This brings us much closer to a blood test than we have ever been."

Fibromyalgia is a common, debilitating, and poorly understood disorder, marked by widespread pain and fatigue, with no known cause and absolutely no cure.

In the United States, it's the most common cause of chronic widespread pain, and that's not even counting the thousands of patients who go undiagnosed every year.

Without a reliable way to detect this disorder, it's estimated that up to three out of four people with the condition remain undiagnosed. And on average it can take five years from when a person's symptoms first appear to them actually receiving a diagnosis.

In total, the US Centers for Disease Control and Prevention estimates that about two percent of the population – around four million adults – have fibromyalgia, with women making up a disproportionate slice.

Left with few options, many patients are simply forced to live with their pain. With nowhere to go, many become desperate and turn to potentially harmful treatments.

"When you look at chronic pain clinics, about 40 percent of patients on opioids meet the diagnostic criteria for fibromyalgia," says Hackshaw.

"Fibromyalgia often gets worse, and certainly doesn't get better, with opioids."

It was Hackshaw's goal to intervene sooner. Using vibrational spectroscopy, a technique which measures the energy of molecules, his team analysed blood samples from 50 people with fibromyalgia, 29 with rheumatoid arthritis, 19 with osteoarthritis, and 23 with lupus.

Despite the fact these disorders can present with similar symptoms, the blood of those participants with fibromyalgia was distinct.

Using these unique patterns, the researchers then tried to blindly predict participants' diagnoses. Even without knowing their true disorder, the researchers were able to accurately diagnose every study participant based on that molecular fingerprint in the blood.

"These initial results are remarkable," says co-author Luis Rodriguez-Saona, an expert in vibrational spectroscopy at Ohio State University.

"If we can help speed diagnosis for these patients, their treatment will be better and they'll likely have better outlooks. There's nothing worse than being in a grey area where you don't know what disease you have."

While the sample size is undoubtedly small, the results are promising. If the team can replicate their results on a larger scale, with a couple hundred diverse participants, then a blood test in five years might not seem so far-fetched.

Not to mention what that would mean for treatment. If the researchers can prove they really have identified a biological fingerprint for fibromyalgia, this could give us new drug targets in the future.

"Thus," the authors conclude, "our studies have great importance both from development of a reproducible biomarker as well as identifying potential new therapeutic targets for treatment."

This study has been published in the Journal of Biological Chemistry.