Differentiation of Geriatric Major Depression From Alzheimer’s Disease With CSF Tau Protein Phosphorylated at Threonine 231

OBJECTIVE: Differentiation of geriatric major depression from Alzheimer’s disease is hampered by overlapping symptoms. Increased CSF concentrations of tau protein phosphorylated at threonine 231 (p-tau₂₃₁) have been suggested as a biomarker for Alzheimer’s disease. The authors asked whether p-tau₂₃₁ levels improve the differential diagnosis between geriatric major depression and Alzheimer’s disease. METHOD: Included were 34 depression subjects, 64 with probable Alzheimer’s disease, 17 with possible Alzheimer’s disease, and 21 healthy comparison subjects. P-tau₂₃₁ concentrations were measured with an enzyme-linked immunosorbent assay. RESULTS: P-tau₂₃₁ levels were significantly higher in Alzheimer’s disease than in geriatric major depression patients and healthy comparison subjects. For differentiation of probable Alzheimer’s disease from major depression, p-tau₂₃₁ correctly allocated 87% of subjects. When possible mild Alzheimer’s disease was compared to major depression, p-tau₂₃₁ correctly allocated 78% of subjects. CONCLUSIONS: CSF p-tau₂₃₁ should be evaluated as a potential biological marker for differentiation of geriatric depression from Alzheimer’s disease.