GFAP and amyotrophic lateral sclerosis: Using regression analysis, we found that GFAP levels were significantly influenced by age at both onset (β = 0.026, 95% CI 0.02 to 0.032, p < 0.0001) and sampling (β = 0.026, 95% CI 0.020 to 0.032, p < 0.001), Revised Amyotrophic Lateral Sclerosis Functional rating (ALSFRS-R) scale (β = −0.031, 95% CI −0.046 to −0.017, p < 0.001), disease progression rate (DPR) (β = 0.119, 95% CI 0.023 to 0.217, p = 0.016), forced vital capacity (FVC) values (β = −0.004, 95% CI −0.008 to −0.001, p = 0.02), and creatinine levels (β = 0.699, 95% CI 0.310 to 1.088, p = 0.0005).