by Sarah Annesley,The Conversation

Credit: Karolina Grabowska from Pexels

Scientists in the United Kingdomsay they have developeda blood test that can diagnose myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)with 96% accuracy—the first of its kind.

For many who live with the debilitating condition, this will be exciting news.

Despite affectingmillions of people worldwide, this condition remains poorly understood. It is characterized by unrelenting fatigue that doesn't improve with rest, and post-exertional malaise—a worsening of symptomsafter even minor physical ormental activity.

Yet with no reliable test, many people wait years for a diagnosis. This usually depends on symptoms meeting certain clinical criteria. Butdiagnostic criteria can be controversial as they vary worldwideand many are outdated.

An accurateblood testcould be a game changer for diagnosis.

So, how excited should we get? Here's what we know.

Currently, you can only receive a diagnosis if you experience disabling fatigue—one of thekey symptomsaccording to most clinical criteria—for at least six months, accompanied by post-exertional malaise.

But people with the condition often experiencea wide range of other symptoms, including headaches, muscle orjoint pain, sleep disturbances, dizziness, a racing heart, and problems with memory, thinking and decision making.

So, clinicians must also rule out other conditions with overlapping symptoms.

This means diagnosis relies heavily on clinicians' knowledge of ME/CFS and their willingness to listen to the patient's complex symptom history. This process cantake years—and the delay in diagnosis has real consequences.

Evidence suggestsearly interventionis key to recovery. Rest during the early stages of the illness likely results in better long-term outcomes, as has been suggested for the clinically similar diseaselong COVID.

One study showed adelayed ME/CFS diagnosiswas linked to poorer outcomes, meaning recovery was less likely and the chance of developing moresevere symptomsincreased.

Without adefinitive diagnosis, patients regularly face disbelief about their illness and have limited access to information, health-care services and medical benefits.

Frequent delays in diagnosis may contribute to the condition's low recovery rate, which isestimated at just 1–10%.

To develop a diagnostic test, the new study identified biomarkers that may be specific to people with this condition.

In this case, the biomarkers relate to epigenetics—changes in the structure of a person's chromosomes, influencing which genes can be turned on or off.

These changes occur due toenvironmental influencessuch as stress, infection and exercise. So, when someone develops ME/CFS, the illness may change the structure of their chromosomes—but until now, researchers hadn't identified what this would look like.

The researchers examinedblood samplesfrom people they knew had ME/CFS and identified around 200 such biomarkers. These changes formed a distinct biological "signature" that was not present in the blood of healthy participants in the comparison group.

This signature was very accurate in correctly identifying which samples were from people with the condition and which were from the comparison group.

According to the researchers, the test's sensitivity was 92%—this is the probability a positive result will show when someone has the condition. It had a specificity of 98%, meaning the probability it can rule out negative cases.

This combined to an overall diagnostic accuracy of 96%.

This research is promising, but it's still very early days. It was a proof-of-concept study, meaning small-scale research to initially test whether an idea might work.

In this case, researchers explored the idea that structural changes in chromosomes could be used as biomarkers of ME/CFS. Their results suggest they can.

However, there were several limitations. The study involved a relatively small number of people: 47 participants with severe ME/CFS and 61 in the healthy "control" group.

The ME/CFS group had more females, and its participants were so severely affected they were housebound. So they presumably had lower activity levels than the control group.

We know a person'ssexandactivity levelscan influence these chromosomal changes, so this may have affected the results.

To develop a diagnostic test that can be used widely, several crucial steps remain.

How much a person's sex and exercise levels influence these biomarkers needs to be determined. The biomarkers will also need to be validated in larger, more diverse groups, which include people with less and more severe symptoms than in this study and those from different backgrounds.

To confirm if these biomarkers are truly specific to ME/CFS, they need to be compared with other conditions that share similar symptoms, such as multiple sclerosis and fibromyalgia.

Finally, it's also important that a test, if developed, should be affordable and accessible.

ME/CFS remains a severely underdiagnosed condition, and the lack of a reliable test continues to delay care and worsen outcomes. Identifying biomarkers, as this study aimed to do, is a promising first step.

This article is republished fromThe Conversationunder a Creative Commons license. Read theoriginal article.

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