Disclosure of plasma p-tau217 measure improves diagnostic confidence in patients with Alzheimer's disease versus syndromes associated with frontotemporal lobar degeneration

Introduction: Further research is needed to understand the performance of plasma phosphorylated tau (p-tau)217 in the diagnostic thinking at the individual patient level. We evaluated the incremental diagnostic value of plasma p-tau217, expressed in terms of diagnostic confidence of Alzheimer's disease (DCAD; range 0-100). Methods: Two hundred thirty-two patients with dementia were included and scored in terms of DCAD in a three-step consecutive assessment: (1) clinical work-up, (2) clinical work-up plus plasma p-tau217, and (3) clinical work-up, plasma p-tau217, plus conventional amyloid markers. Two blinded neurologists were asked to review DCAD at each step. Results: DCAD accuracy, expressed as area under the curve, significantly increased from 0.93 with clinical work-up alone, to 0.97 with clinical work-up plus plasma p-tau217 (P = 0.01), with no further increase with the addition of conventional amyloid markers (0.99, P = 0.13). Discussion: Plasma p-tau217 in addition to routine assessment significantly enhances diagnostic confidence that is comparable to well-established amyloidosis biomarkers. Highlights: Plasma phosphorylated tau (p-tau)217 measurements increase diagnostic confidence of Alzheimer's disease. Plasma p-tau217 increases diagnostic confidence comparable to traditional markers. Plasma p-tau217 dosage may be helpful in addition to routine assessment.