Researchers have identified biological markers in both gut bacteria and blood that can be used to diagnose chronic fatigue syndrome - also known as myalgic encephalomyelitis, or ME/CFS - in more than 80 percent of patients tested.
But this new research will allow patients to be diagnosed more rapidly, and with greater accuracy - and could eventually lead to a better understanding of exactly what causes the mysterious condition.
In the new study, researchers at Cornell University used biological markers for diversity in gut bacteria, as well as blood-based inflammatory markers - such as lipopolysaccharides and C-reactive protein - to diagnose the presence or absence of ME/CFS in 87 patients.
Out of the group, 48 had ME/CFS, and 39 were healthy controls - and simply by looking at their biological markers, the team could predict which was which with an 83 percent accuracy rate.
Not only is that exciting in terms of future diagnostic tests, but it also suggests a link between gut bacteria health and ME/CFS.
"Our work demonstrates that the gut bacterial microbiome in chronic fatigue syndrome patients isn't normal, perhaps leading to gastrointestinal and inflammatory symptoms in victims of the disease," said Maureen Hanson, the paper's senior author.
"Furthermore, our detection of a biological abnormality provides further evidence against the ridiculous concept that the disease is psychological in origin."
That's important, because many doctors still think of chronic fatigue as nothing more than extreme "exhaustion".
But the researchers found that ME/CFS patients had less diversity in their gut bacteria than the control group - specifically, fewer bacterial species that were anti-inflammatory and more which were pro-inflammatory.
They could also identify changes and specific markers of inflammation in the blood, which the researchers think could be due to intestinal problems leaking bacteria into the blood – which triggers an immune response, and might worsen symptoms in patients.
"In the future, we could see this technique as a complement to other non-invasive diagnoses, but if we have a better idea of what is going on with these gut microbes and patients, maybe clinicians could consider changing diets, using prebiotics such as dietary fibres or probiotics to help treat the disease," said Ludovic Giloteaux, first author for the new research.
This isn't the first time that scientists have come up with a biological way to diagnose ME/CFS. Earlier this year a group of Australian scientists used SNPs (single nucleotide polymorphisms - which are single letter changes to DNA) to be able to detect ME/CFS in up to 80 percent of cases.
As far as we're concerned though, the more tests the better, because that means patients can get diagnosed quicker.
As Bec Crew explained for us back in March:
"While we're still a long way off finding a cure for the disease, the serious lack of adequate diagnostic and screening tools has made living with chronic fatigue syndrome even more difficult, because the uncertainty surrounding it has led many to assume it's not a 'real' disease. "Patients are isolated and further stigmatised by disbelief of their condition," says Sonya Marshall-Gradisnik from Griffith University."
The more scientists understand about this disease, the more likely it is we will be able to find a way to treat it.
Already researchers have found that for some ME/CFS sufferers, a particular type of cancer drug called rituximab - which wipes out a type of white blood cell - can ease symptoms, further suggesting that this disease is linked to the immune system.
To be clear, the researchers still aren't sure if this change in gut bacteria is one of the causes of ME/CFS, or whether it's a symptom. And further research is required to figure out what's going on.
The study has been published in Microbiome.