Modeling analyte levels across the transition from presymptomatic to symptomatic ALS (n = 5, 3–7 observations per participant for each analyte), there was an increase in CSF CHIT1 levels of 0.403 log10 [CHIT1] per year (P = 0.005; Fig. 3C), and CHIT1 activity 0.260 log10 [CHIT1 activity] per year (P = 0.007; Fig. 3G). This evidence concerns the gene CHIT1 and amyotrophic lateral sclerosis.