MAPT and Alzheimer disease: Previously, clinical groups were mostly defined based on clinical diagnosis, and the only differences in CSF PDGFRβ in groups defined by biomarkers were between A+/T+/N+ and A−/T−/N− (i.e., a difference was only seen when amyloid, tau, and neurodegeneration CSF biomarkers were pathologic, but not when only core AD biomarkers were abnormal) or within cohorts defined by A/T/N that only included preclinical AD.3,5,9,10,22 Most importantly, this is one of the few and the largest study using PET imaging and not only CSF biomarkers.