NEFL and amyotrophic lateral sclerosis: After adjusting for the factors of age and sex, the results still showed a significant difference in NFL serum concentrations between the ALS patients and the HCs {median [interquartile range (IQR)]: 63.3 (46.9–98.1) pg/mL vs. 5.3 (4.5–7.1) pg/mL, P < 0.001} (Figure 1).