MAPT and Alzheimer disease: CSF Aβ40 normalization significantly strengthened the associations of several core CSF AD biomarkers, including CSF MTBR-tau243, p-tau isoforms and synaptic biomarkers, with tau-PET (ΔR2 = 0.064-0.24) and Aβ-PET (ΔR2 = 0.016-0.28).