Current ALS diagnosis relies on neurological evaluations and the presence of symptoms; at present, there is no definitive diagnostic test. Results of the new study, published Aug. 19 in Nature Medicine, lay the foundation for a much-needed diagnostic test for ALS. The findings suggest the biological markers of ALS can be detected up to a decade before clinical symptoms appear. Among these pre-symptomatic individuals, researchers observed previously unknown (before this study) changes in blood proteins before the patients later developed symptoms. These findings suggest the biological markers of ALS can be detected up to a decade before clinical symptoms appear.