The increased sensitivity of the last-generation assays, and the prospective nature of the study allowed to establish that the concentration of serum NfL during prodromal stages in converters was well-above that of age-matched controls, which was in contrast to a previous study in which NF levels in carriers of ALS-causing mutations were not elevated till symptom onset [94]. The gene discussed is NEFL; the disease is amyotrophic lateral sclerosis.