Performance of Elecsys pTau217 plasma immunoassay to detect brain amyloid pathology

INTRODUCTION: We evaluated clinical performance of the fully-automated, high-throughput, prototype Elecsys Phospho-Tau (217P) plasma immunoassay (Roche Diagnostics) for detecting amyloid pathology. METHODS: Plasma pTau217 levels were determined in samples from cognitively impaired and unimpaired individuals from five cohorts (N=7252) using the pTau217 plasma immunoassay. Clinical performance was evaluated against amyloid positron emission tomography. RESULTS: For cognitively impaired, mean plasma pTau217 levels for amyloid-positive (A+) were higher (n=394; 0.835 pg/mL) than amyloid-negative (A−) individuals (n=144; 0.361 pg/mL); similarly, for cognitively unimpaired, A+ (n=224; 0.516 pg/mL) and A− individuals (n=1386; 0.220 pg/mL). Area under curve was 0.878 (95% confidence interval [CI] 0.840, 0.915) (impaired) and 0.907 (95% CI 0.885, 0.929) (unimpaired). Cutoff < 0.189 pg/mL reliably ruled-out individuals without amyloid pathology. High negative predictive values [92.51% (impaired); 98.60% (unimpaired)] were observed with sensitivity/specificity of 98.98%/29.17% and 95.54%/50.72%, respectively. DISCUSSION: The pTau217 plasma immunoassay accurately detects amyloid pathology, irrespective of cognitive status.