MAPT and Alzheimer disease: There has been increasing use of positron emission tomography (PET) to detect fibrillar Aβ and tau pathologies in living subjects, along with biochemical measurements of Aβ42, Aβ40, tau, and ptau in the cerebrospinal fluid (CSF), for research and clinical studies of AD (Galasko et al., 1998; Shaw et al., 2009; Trojanowski et al., 2010; Molinuevo et al., 2014; Beckett et al., 2015; Kang et al., 2015; Kleinschmidt et al., 2015; Weiner et al., 2015; Leuzy et al., 2016).