GFAP and tauopathy: Plasma p‐tau217 (P < 0.001), p‐tau181 (P = 0.001), Aβ42/40 ratio (P < 0.001), and GFAP (P = 0.024) levels were significantly different when comparing participants with only AD pathology and participants with only primary tauopathies (Appendix Fig S16).