A quick and simple blood test could help detect deadly ALS up to five years before the condition appears, a study suggests.
Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disorder that gradually destroys the nerve cells controlling movement. In just two to five years, the disease robs patients of their ability to walk, talk, swallow and, ultimately, breathe.
The initial signs of ALS – slight twitching, dropping items, slurred speech – are subtle and easy to dismiss, meaning it can take months or years before patients finally get a diagnosis and treatment. There is no cure for the condition, but treatments can help to slow its progression in sufferers.
Now, researchers in Florida say they may have found a new way to detect ALS faster.
In an analysis of 20 years of blood samples from people with pre-symptomatic ALS, the team identified nearly 100 proteins that changed before symptoms of the condition appeared.
From this, they were able to develop a 19-protein blood panel, which they said could be used to detect ALS in people genetically at risk years before symptoms develop.
The study comes as the US faces an explosion of ALS diagnoses. Around 33,000 Americans were living with ALS, also known as Lou Gehrig’s disease, in 2022, according to the national ALS Registry.
That number is expected to climb to more than 36,000 by the end of the decade.
Chris Johnson on the field during a Tennessee Titans game in 2013. The star was diagnosed with ALS in 2025 at the age of 39 years
About nine in ten cases are sporadic ALS, meaning someone develops the disease without a clear family history. One in 10 cases are linked to people with a family history of the disease.
‘By studying blood samples from people at elevated genetic risk for ALS, we identified protein signatures that predict whether someone is going to phenoconvert in the relatively near future,’ Dr Michael Benatar, senior study author and executive director of the ALS Center at the University of Miami, said.
‘This could be an incredibly valuable tool for us to select appropriate people for inclusion in future ALS prevention trials and ultimately to develop effective treatments.’
It’s unclear when the test may be available to the public. ALS is usually diagnosed through neurological tests such as nerve conduction studies, MRI scans and analyzing cerebrospinal fluid.
In the new study, published in Nature Medicine, researchers analyzed data from the Pre-symptomatic Familial ALS (Pre-fALS) study, which follows people with a high genetic risk of ALS for nearly 20 years.
The researchers examined plasma samples from 137 people in the Pre-fALS study, including 33 who later developed clinical signs of ALS or frontotemporal dementia.
They then analyzed levels of more than 5,000 proteins in the blood, identifying 92 whose levels differed before participants went on to develop symptomatic ALS.
The team then used machine learning to narrow that list down to 19 proteins, including neurofilament light chain, and develop a blood test to measure their levels.
With the information from those 19 proteins, the researchers were able to estimate when people would begin showing signs of ALS with an average error of 18 months.
The predictions ranged from six months to five years before symptom onset.
Benatar said the early blood panel is an important step toward developing better tests to narrow down the exact timing of ALS symptom onset, which may inform clinical trials and treatments.
Currently there is no cure for ALS, and treatments focus on slowing the symptoms.
Eric Dane, best known for his role as Dr Mark Sloan on Grey’s Anatomy, attends a premiere in June 2025. He was diagnosed with ALS in 2024 at age 51. He died in February this year, aged 53, from respiratory failure, which can be triggered by the condition
‘Without these markers, it would be difficult to run a trial because we’d have no idea who would actually develop ALS or FTD and when,’ Benatar said.
‘Because we can now predict when phenoconversion is likely, we have a much better sense of who to enroll, and we have a measurable way to know if a therapy is working.’
The researchers are now working on testing cerebrospinal fluid from pre-fALS participants to find other important protein markers.
‘We do this work in partnership with, and in service to, the carrier community,’ Benatar said. ‘They’re regular people, with busy family and professional lives. Some come from far away.
‘But every year, they take a few days off to see us because they are profoundly committed to the idea that, someday, we can more effectively treat and possibly even prevent this disease.’