This study assesses the performance of serum neurofilament light chain (sNfL) in amyotrophic lateral sclerosis (ALS) in a wide range of disease courses, in terms of ALS progression, disease duration, and tracheostomy invasive ventilation (TIV). The aim of the research project is to investigate the correlation between NfL serum concentration and the natural course of the disease, the ALS progression rate, and specific phenotypes of ALS. Furthermore, the performance of NfL as a therapeutic biomarker will be studied. A systematic analysis of the NfL serum concentration in a cohort of 3,000 ALS patients using the Single Molecule Analysis method (SIMOA) will be performed. This analysis is carried out as a multi-center study.