A 19-protein blood panel estimated ALS symptom timing with a 1.6-year average error

In people at high genetic risk for ALS, a 19-protein blood panel estimated the timing of clinical symptoms with a mean absolute error of 1.62 years.

This is not an early diagnostic test for everyone: it is a research result intended to improve the timing and selection of genetic carriers for prevention trials.

What the researchers found

Using the Pre-fALS cohort followed from before symptoms through clinical onset for about 18 years, researchers identified 92 proteins that changed before phenoconversion and narrowed them to a core panel of 19.

The panel distinguished the probability of clinical ALS within 0.5, 1, 2, 3 and 5 years. Crossvalidated areas under the curve ranged from 0.80 to 0.89.

The study size and what 1.6 years means

The analysis used 516 serial plasma samples from 33 phenoconverters, 35 people with clinical ALS, 10 presymptomatic genetic carriers and 59 controls.

A mean absolute error of 1.62 years does not guarantee an individual onset date within that window. It is the average absolute difference between predicted and observed conversion times in the discovery cohort.

Why prevention trials need this

ALS symptoms appear after motor-neuron injury has begun. Even among carriers of high-risk variants, uncertainty about who will develop symptoms and when makes presymptomatic trials large and slow.

Finding people likely to convert soon could test preventive candidates at a more informative time. This study did not show that any treatment prevents or delays ALS.

The external data had a larger error

UK Biobank data partially reproduced several presymptomatic protein changes and the advantage of a multi-protein panel over neurofilament light alone.

But the replication was cross-sectional and assumed conversion two years before a relevant hospitalization. Its 15-protein panel had a mean absolute error of 2.75 years, larger than in the discovery study.

Why this is not yet a diagnostic test

The discovery cohort was small and centered on carriers of familial ALS-associated variants, so the result cannot be transferred directly to sporadic ALS or population screening. Standardized assays and independent prospective validation are still needed.

As of July 29, 2026, the panel is not an approved diagnostic or screening test. Genetic testing and ALS risk counseling carry uncertainty and family implications and should use specialist clinical and genetic-counseling pathways.

Official primary sources

Nature Medicine: original longitudinal plasma proteomics study

NIH: study design, results and relevance to prevention trials

University of Miami: researcher context, scope and clinical limits