Table 1.

Potential biomarkers with their features.

Amyloid-Beta	Tau Protein	Phosphorylated Tau
Aβ plaque depositions commonly define AD. The amyloidogenic pathways produce these 42-amino-acid peptides (Aβ1-42), clumping in the brain. The amount of Aβ in AD patients’ CSF is reduced by roughly 500 pg/mL compared with healthy controls (79,420 pg/mL) [121].	Tau inclusion intraneuronal microtubule-associated protein is another well-established AD biomarker. There is an exponential increase in tau protein levels in AD patients from 300 to 600 pg/mL, which grows with age from 21–50 years to >71 years (in patients aged 51–70 years). Therefore it is an excellent prognostic biomarker [122].	In AD, tau protein is phosphorylated in about 39 places. Position 181 is a distinct biomarker in AD versus controls. Tau protein phosphorylation causes function loss and neuronal malfunction. There are also phosphorylated tau-199, tau-231, tau-235, tau-396 and tau-400 [123].