There is no blood test for ALS. Diagnosis today is a slow process of elimination: a neurologist’s examination, electrical tests of muscles and nerves, and months spent ruling out everything else it could be. For a disease that typically kills within two to five years of diagnosis, those lost months are brutally expensive.
A study from Emory University, published in Nature Communications, points to a way to compress that timeline. Researchers measured more than 300 neurological and inflammatory proteins in blood samples from hundreds of people, using an ultra-sensitive platform called NULISA, and found that just ten proteins, taken together, could distinguish people with amyotrophic lateral sclerosis — ALS, also known as Lou Gehrig’s disease — from healthy controls with 98.3% balanced accuracy in an independent validation cohort. The same signature separated ALS from healthy controls with an area under the curve of 0.992, a statistical measure where 1.0 is perfect.
The ten include proteins doctors already associate with nerve damage, such as neurofilament and phosphorylated tau, alongside others that had never before been linked to ALS in blood. “We saw the proteins we expected, like neurofilament and phosphorylated tau, but we also found differences in proteins that hadn’t been linked to ALS in blood before,” said Dr Eleanor Varian Thomas, assistant professor at Emory University School of Medicine. “The combination of established and new biomarkers into a single protein signature identified ALS far more accurately than neurofilament alone.”
The study drew on more than 750 ALS cases, and the researchers say several of the newly identified proteins may also reveal something about ALS biology itself — how motor neurons, the cells that control voluntary movement, break down. That matters because a diagnostic marker that also teaches scientists about the disease is worth more than a marker that merely correlates with it.
Now the sentence that matters most for anyone reading this with hope: this is a research finding, not a clinical test. The researchers themselves stress that the signature “remains a research finding, not a clinically validated screening or diagnostic test”. It has not yet been tested in the larger, more diverse patient groups that regulators and doctors would require, and it has not been shown to work as a screening tool for people without symptoms. A blood-based biomarker panel could one day help clinicians refer patients to specialists sooner, and help clinical trials enrol people earlier, when experimental treatments have the best chance of working. That day is closer after this study — but it has not arrived yet.
What happens next: validation in bigger cohorts, testing against the many conditions that mimic ALS, and the long, unglamorous work of turning a laboratory signature into something a hospital lab can run reliably. If that work succeeds, the first sign of ALS might one day be found in a routine blood draw, months before a neurologist could confirm it any other way.
