There is still no single test that reliably diagnoses ALS. After the first symptoms appear, patients wait nearly a year for an answer, because muscle weakness, cramps and difficulty walking fit dozens of other conditions. A blood test that shortened that wait would not be a lab curiosity; it would be a different illness story.
Researchers at Emory University School of Medicine have now put forward a candidate. They analysed hundreds of proteins in blood plasma from 632 people with ALS and 160 healthy individuals, and identified ten proteins that, taken together, separated the two groups with roughly 98 percent balanced accuracy. The work was published this week in Nature Communications.
How it was measured matters. The team used an assay called NULISA — Nucleic Acid Linked Immuno-Sandwich Assay — which can detect extremely small quantities of protein in blood. That is important for ALS, because the best markers available so far, such as neurofilament light chain (NfL), sit in blood at far lower concentrations than ordinary proteins. The ten-protein combination performed substantially better than NfL alone, which can also be elevated in other neurological conditions.
The underlying idea is deliberately broad. "ALS is a complex disease, and relying on a single biomarker doesn't capture the full picture," said Eleanor Thomas, a neurologist at Emory and co-principal investigator. The ten proteins cover different aspects of the disease, including nerve-cell injury and inflammation. That is where the plausibility lies: a panel can represent patterns a single value cannot.
The limits matter, and the researchers name them. The comparison was ALS against healthy controls — not against the conditions that are actually confused with it in clinic: other motor neuron diseases, myopathies, neuropathies. Until that comparison exists, it is not established that the panel can tell ALS apart from its mimics in practice. Further studies would have to show that before anyone treats it as a screening tool. The cohort is also unusually favourable for this kind of panel — 632 patients from a single centre at one US academic medical centre; population-based cohorts look different.
What the work does settle is a direction. The route to an ALS blood test has run through a single marker, usually NfL, and hit a wall there: sensitive, but not specific. A combined ten-protein panel moves the question from "is this one value elevated?" to "does this pattern fit?" That is harder methodologically and more promising practically.
For patients, nothing changes today. There is no approved test, and this is not a regulatory study. But the direction in which the diagnostic wait could shorten now has numbers behind it: 98 percent against healthy controls, clearly better than the previous favourite, measured with a technique that already exists in laboratories. Funding came from Hop On A Cure, the Muscular Dystrophy Association, the American Brain Foundation, the ALS Association and the American Academy of Neurology, among others.
