Impact of plasma pTau181 levels on clinician diagnostic confidence and management in memory and cognition clinics: A multi‐site before‐and‐after study

Abstract INTRODUCTION Recent advances allow blood tests to detect key proteins linked to Alzheimer's disease (AD). METHODS In this before‐and‐after study across three Australian memory and cognition clinics, we evaluated the impact on clinicians' diagnostic confidence and management following disclosure of routine patients' AD probability, using predefined plasma phosphorylated tau 181 (pTau181) thresholds set at 90% sensitivity and 90% specificity for amyloid‐beta (Aβ) positron emission tomography (PET) positivity. RESULTS One hundred thirteen participants (mean age: 71.2 ± 8.4; mean Mini‐Mental State Examination score: 27.7 ± 2.5) with dementia ( n = 17, 15.0%), mild cognitive impairment ( n = 48, 42.5%), and subjective cognitive decline ( n = 48, 42.5%) were enrolled. Blood test results were “probably negative,” n = 81, 71.7%; “indeterminate”, n = 24, 21.2%; and “probably positive,” n = 8, 7.1%. In 12 cases (10.6%), pTau181 changed clinician diagnosis and increased mean diagnostic confidence from low‐to‐moderate (61%) to moderate‐to‐high (80%). Aβ PET in 40 participants showed plasma pTau181 improved diagnostic accuracy by 5%. DISCUSSION This study demonstrates the benefits of plasma pTau181 in real‐world clinical practice particularly when diagnostic confidence is only low‐to‐moderate.