Researchers have developed the first blood test that could help diagnose myalgic encephalomyelitis, also known as chronic fatigue syndrome.

The condition is thought to affect more than 400,000 people in Britain but there is at present no diagnostic test, meaning patients often go undiagnosed for years and have their symptoms dismissed by doctors.

However, academics at the University of East Anglia have made an advance in the diagnosis of ME by developing a blood test which identifies genetic markers for the condition.

Experts have cautioned that the research is still in its early stages, and larger studies will be needed before the test could be used widely on the NHS.

Professor Dmitry Pshezhetskiy, a lead researcher, said: “ME/CFS is a serious and often disabling illness characterised by extreme fatigue that is not relieved by rest.

“We know that some patients report being ignored or even told that their illness is ‘all in their head’; with no definitive tests, many patients have gone undiagnosed or misdiagnosed for years. We wanted to see if we could develop a blood test to diagnose the condition — and we did.

“Our discovery offers the potential for a simple, accurate blood test to help confirm a diagnosis, which could lead to earlier support and more effective management.”

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Scientists from UEA and Oxford Biodynamics (OBD) set out to examine how DNA is folded in patients diagnosed with the condition, which could provide telltale signs of ME.

Using OBD’s EpiSwitch 3D Genomics technology, they looked at blood samples from 47 patients with severe ME/CFS and 61 healthy adults.

The team discovered a unique pattern that appears consistently in people with ME that is not seen in healthy people, enabling them to develop the test.

Writing in the Journal of Translational Medicine, experts said that the test had a sensitivity — or the likelihood of a test being positive if that patient has the condition — of 92 per cent.

It also has a specificity — the probability that the test will rule out negative cases — of 98 per cent.

Pshezhetskiy added: “This is a significant step forward; for the first time, we have a simple blood test that can reliably identify ME/CFS — potentially transforming how we diagnose and manage this complex disease.

“Additionally, understanding the biological pathways involved in ME/CFS opens the door to developing targeted treatments and identifying which patients might benefit most from specific therapies.

“We hope that the Episwitch CFS test could become a vital tool in clinical settings, paving the way for more personalised and effective care.”

Alexandre Akoulitchev, the OBD chief scientific officer, added: “Chronic fatigue syndrome is not a genetic disease you’re born with, that’s why using EpiSwitch ‘epigenetic’ markers — which can change during a person’s life, unlike fixed genetic code — was key to reaching this high level of accuracy.

“With this breakthrough, we are proud to enable a first-in-class test that can address an unmet need for a quick and reliable diagnostic for a complex, challenging-to-identify illness.”

Commenting on the finding, Dr Charles Shepherd, medical adviser for the ME Association, said: “These results, using epigenetic profiling, appear to be an important step forward in the search for a diagnostic blood test.

“However, as the researchers point out, a diagnostic blood test has to be both highly sensitive and specific to that condition.

“In this case, we therefore need to know whether the abnormality is consistently present in the very early stages of ME/CFS as well as in people with longstanding disease who have mild or moderate ME/CFS.”

Professor Chris Ponting, chairman of medical bioinformatics at the University of Edinburgh, added: “This test needs to be fully validated in better-designed and independent studies before it is considered for clinical application.

“Even if validated, the test will be expensive, likely about £1,000.”

ME leads to symptoms including exhaustion and pain. Severe cases can be fatal, with patients bedridden and unable to eat or drink. It has taken decades to overturn a misconception in medicine that ME is a psychological or behavioural disorder.

This summer, a major study by the University of Edinburgh found that genetic factors increase the risk of myalgic encephalomyelitis in the biggest scientific breakthrough yet into the disease.

The study involved analysing the DNA of more than 15,000 people with ME, finding eight “signals” in genetic code where people with ME tended to have markedly different gene variants compared with the healthy population. It is the first robust evidence that genes predispose people to the disease, and suggests that ME may be caused by processes in the immune system and nervous systems.