GFAP and amyotrophic lateral sclerosis: Plasma GFAP showed very high accuracy (AUC 0.932 ± 0.027) in discriminating A+T+ patients (AD/ALS) from those not displaying a CSF profile consistent with a full-blown AD pathology (not-AD/ALS, namely A− and A+T− ALS patients), which was significantly higher than that of any other plasma biomarker (plasma p-tau181 AUC 0.692 ± 0.058, plasma GFAP vs. plasma p-tau181 p = 0.0008; plasma NfL AUC 0.548 ± 0.088, plasma GFAP vs. plasma NfL p < 0.0001) (Table 4, Figure 2d–f).