All AD biomarkers were correlated to each other (p value < 0.001 for all, Figure 2); the strongest correlations were observed between NfL and GFAP (Spearman's rho = 0.654), p‐tau181 and t‐tau (Spearman's rho = 0.609), and p‐tau181 and NfL (Spearman's rho = 0.531). Here, GFAP is linked to Alzheimer disease.