Plasma Phospho-Tau Identifies Alzheimer's Co-Pathology in Patients with Lewy Body Disease

Background: Alzheimer's disease co-pathology is common in dementia with Lewy bodies and Parkinson's disease with dementia (Lewy body disease) and can reliably be detected with positron emission tomography (PET) or cerebrospinal fluid (CSF) biomarkers. Recently developed blood biomarkers are more accessible and less expensive alternatives. Objective: To investigate if plasma phospho-tau217 and phospho-tau181 can detect Alzheimer's pathology in Lewy body disease with dementia. Methods: In this cross-sectional study we investigated plasma phospho-tau217 and phospho-tau181 in 35 patients with Lewy body disease with dementia. Patients underwent tau-PET imaging (¹⁸F-RO948). Results: Plasma phospho-tau217 correlated with plasma phospho-tau181, CSF phospho-tau217 (r_s = 0.68, P < 0.001), and negatively with CSF β-amyloid_42/40 (r_s = −0.52, P = 0.001). Plasma phospho-tau217 and phospho-tau181 correlated with tau-PET signal in the temporal cortex (r_s > 0.56, P < 0.001) and predicted abnormal tau-PET status and β-amyloid status (area under the curve > 0.78 and > 0.81, respectively). Conclusion: Plasma phospho-tau might be a useful marker for Alzheimer's co-pathology in Lewy body disease with dementia.