SPEAR UltraDetect™ pTau 217: A High-accuracy, Scalable Plasma Biomarker for PET Confirmed Patients

Presented at AAIC 2025

Background:
Alzheimer’s disease misdiagnosis in specialized clinics and primary care often delays confirmatory testing and treatment windows for anti-amyloid therapies. Plasma pTau-217 assays offer a minimally invasive, scalable alternative for detecting amyloid pathology, yet their cost-effectiveness in reducing confirmatory testing remains uncertain. Many current assays fail to surpass 90% sensitivity and specificity with a single cutoff, relying instead on a tiered double-cutoff approach that inflates accuracy by discounting the intermediate zone (>20%). Stricter thresholds further expand this gray zone, leaving a substantial number of patients with delayed treatment decisions. To improve diagnostic accuracy, normalization strategies incorporating non-phosphorylated tau or amyloid-beta ratios were explored to mitigate false positives from commodities like CKD beyond pTau-217 alone.

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