APP and Alzheimer disease: For example, CSF measurements of amyloid beta peptide (Aβ)1‐42, microtubule associated protein tau, and phosphorylated forms of tau (p‐tau) are used to aid in the diagnosis of Alzheimer's disease (AD) (Blennow et al., 2015, 1995; Hansson et al., 2019; Maddalena et al., 2003). Diagnosis of Creutzfeldt‐Jakob disease utilises the presence of a normal intracellular protein (14‐3‐3 gamma) that spills into the CSF during rapid neurodegeneration (Hsich et al., 1996; Muayqil et al., 2012) or the aggregated form of prion proteins (Atarashi et al., 2011; McGuire et al., 2012).