NEFL and Alzheimer disease: A comprehensive systematic review and meta-analysis showed the following AD biomarkers to be promising: (i) in CSF Aβ42, T-tau, P-tau, and tau/Aβ42; (ii) in peripheral blood T-tau, Aβ42/Aβ40, and NfL; (iii) in the whole brain, left and right hippocampal volume, entorhinal cortex volume, medial temporal lobe atrophy, 18F-FDG PET, 11C-PiB PET, and (iv) APOE ε4 [126].