Brain derived phosphorylated tau-217 (BD pTau-217) is one of the emerging blood-based biomarkers for Alzheimer’s disease. Similar to pTau-217, BD pTau-217 shows strong correlation with tau pathology and amyloid-associated changes in the brain. Preliminary studies have shown that BD pTau-217 may be better than pTau-217 at differentiating disease states.