NFASC and amyotrophic lateral sclerosis: Thus, precise determination of NFH concentrations by immuno‐based methods can be influenced by several factors: the ability of the aggregate to mask the NFH epitope; the aggregate's decreased solubility; the difference in stability of NFH monomers in solution versus NFH in aggregates; and the ability of the antibody to bind to soluble NFH.23 Lu et al23 confirmed that NF aggregates are characteristic of amyotrophic lateral sclerosis and other neurodegenerative diseases and that they represent a significant pre‐analytical problem for immunoassay analysis.