Abstract
BACKGROUND: Our objectives were to determine the diagnostic accuracy of plasma p‐tau217 and its discriminative power for the Alzheimer's disease‐related pathology, and to determine the cut‐off that optimize the concordance with Aβ42/Aβ40 positive vs negative status. METHOD: 127 patients with AD (n = 30), MCI (n = 81), and non‐AD dementias (n = 16) were included. Aβ42, Aβ40, total tau, and phosphorylated tau181 (p‐tau181) were quantified in CSF and Aβ42, Aβ40, p‐tau181, and p‐tau217 were measured in plasma using the Lumipulse platform (Fujireibio). RESULT: We found a significant correlation between plasma levels of p‐tau217 and CSF levels of p‐tau181 (r = 0.539), Aβ42 (r = −0.443), and Aβ42/Aβ40 (r = −0.594). Regarding diagnostic accuracy, the discriminatory power of p‐tau217 in separating AD from non‐AD dementia patients (AUC 0.856, 95% CI 0.715‐0.996) was comparable with CSF Aβ42/Aβ40 (AUC 0.879, 95% CI 0.592‐0.887) and significantly different from plasma p‐tau181 (AUC 0.662, 95% CI 0.500‐0.823). In addition, the plasma levels of p‐tau217 were associated with the brain AD‐related pathology quantified in CSF. Finally, plasma p‐tau217 (AUC 0.919, 95% CI 0.857‐0.981) showed a high consistency with amyloid pathology (CSF Aβ42/40) at ≥ 0.234 pg/mL cut‐off. The two cut‐offs approach (> 0.314 pg/mL positive and < 0.161 pg/mL negative for p‐tau217) revealed that nearly 84.7% of the patients can be diagnosed as negative or positive for p‐tau217 with a sensitivity and specificity of 94.7% and 93.9%, respectively. CONCLUSION: p‐tau217 blood biomarker has a high diagnostic accuracy and, therefore, it can be a useful tool for screening of those patients that will need a lumbar puncture for AD diagnosis.