New blood test detects ALS with 98% accuracy, offering hope for earlier diagnosis

A simple blood test could speed the diagnosis of the deadly nerve disease amyotrophic lateral sclerosis (ALS), new research suggests. If the test gets regulatory approval, it could help patients start treatment that slows the disease's progression earlier than they would with conventional diagnostics, its developers say.

The new test works by detecting eight small molecules known as microRNAs , which help regulate which genes are turned on and how active they are. These eight molecules are found within tiny packages that are released into the blood from cells of the nervous system in patients with ALS. They act like a "fingerprint" of the disease that can then be detected in the blood.

In a new study, published Thursday (Sept. 12) in the journal Brain Communications , the test was 98% accurate at distinguishing between blood samples taken from 119 people with diagnosed ALS and samples from 150 people without the disease. However, it's not yet known whether the test can accurately differentiate people with ALS from those with other neurological diseases, such as Parkinson's, so more tests will be needed.

The researchers who developed the test say that, with further evaluation, it could become a useful tool for diagnosing ALS. There is currently no cure for the disease, but earlier diagnosis could help hasten patients' access to treatments that help slow physical decline . Such treatments include drugs such as riluzole and edaravone.

Related: Some people recover from ALS — now, we might know why

ALS is a neurodegenerative disorder that affects the neurons in the brain and spinal cord that control the voluntary movement of muscles, including those required for breathing . Initially, patients may experience symptoms such as muscle twitching and cramping. Over time, the disease progresses, causing patients to struggle with everyday tasks, such as eating, speaking and, eventually, breathing.

Most patients with ALS die of respiratory failure within three to five years of their symptoms first appearing.

The disease is currently diagnosed through an extensive clinical examination conducted by a neurologist, Sandra Banack , lead study author and a scientist at Brain Chemistry Labs, a nonprofit research institute in Wyoming, told Live Science in an email. However, the symptoms of ALS often mimic those of other neurological diseases, such as multiple sclerosis and Parkinson's disease , which also cause nerve damage. This is especially true in the earlier stages of these diseases .

So, to confidently diagnose ALS, neurologists must monitor how patients' symptoms progress over time, Banack said. But because patients' short survival time after their symptoms begin is short, many patients "deteriorate significantly" before they can secure a diagnosis, she said.

Thus, a blood test that could help reveal ALS sooner could be a "game-changer, ultimately improving time to diagnosis, reducing patient and family anxiety, lowering diagnostic costs, and supporting the development of new drugs," Banack said.

On that last note, the tests could help flag specific biological pathways that could be targeted by new drugs. For instance, the eight microRNAs are known to be involved in processes such as neuroinflammation and programmed cell death, or apoptosis, which play a role in ALS.

As part of their new study, the researchers also investigated whether the blood test could accurately distinguish between patients with ALS and those with either Parkinson's disease or a very similar condition to ALS known as primary lateral sclerosis (PLS). However, their sample sizes of patients with Parkinson's and PLS were too small to make conclusions about the tests' accuracy at this stage, Banack noted.

Ideally, the blood test would be able to reliably spot cases of ALS and also identify people who definitely do not have the disease. You wouldn't want the test to erroneously flag a case of Parkinson's as ALS, for instance. Thus, the researchers intend to continue assessing the accuracy of the test with more blood samples from people with ALS and people with different diseases.

They hope to bring the test to market as soon as possible.

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"We are actively searching for the right diagnostic company partner who can rapidly make this test available to patients and clinicians," Banack said. "In the best case scenario, it could be available in about 18 months."

The team envisions that clinicians could use the test to quickly confirm or dispel any doubts they may have about a patient's ALS diagnosis after initial examinations.

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