NEFL and Niemann-Pick disease, type C1: The 9 asymptomatic individuals with NPC1 had a mean NfL level of 18.8 ± 29.3 pg/mL (median [IRQ] 8.5 [4.8-16.9] pg/mL) and was different from the control group (n = 24, P = .002, t test) and the symptomatic NPC1 group (n = 109, P = .0086, t test).