MAPT and Alzheimer disease: However, while imaging techniques can be indicative of BBB breakdown related to AD, their use as a solitary diagnostic tool of AD is not definitive and must also be confirmed with additional biomarkers such as Aβ, tau, CSF albumin, and PDGF-B (Montagne et al., 2016a, 2020; Sweeney et al., 2018, 2020; Varatharaj et al., 2019).