Interchangeability of CSF and PET to identify Alzheimer's disease pathology.

INTRODUCTION: Establishing interchangeability between cerebrospinal fluid (CSF) and positron emission tomography (PET) for patient identification may improve access to Alzheimer's disease (AD) therapies. METHODS: Alzheimer's Disease Neuroimaging Initiative participants with mild cognitive impairment or AD dementia and available CSF, florbetapir PET, and/or flortaucipir PET were included. The interchangeability of CSF (per label threshold/method) and PET was evaluated for patient identification. RESULTS: Fujirebio Lumipulse amyloid beta (Aβ) 42/Aβ40 (N = 288) and Roche Elecsys phosphorylated tau 181 (P-tau181)/Aβ42 (N = 251) Conformité Européene (CE)-marked CSF assays were in high agreement with and non-inferior to florbetapir PET for identifying patients with AD pathology. High agreement was observed between Roche Elecsys CSF P-tau181/Aβ42 (N = 127) and an early (temporal) flortaucipir PET stratification. DISCUSSION: CSF assays were interchangeable with amyloid PET to identify patients with AD pathology and were in high agreement with elevated early temporal flortaucipir PET. CSF biomarkers may be used as a robust alternative to PET, potentially increasing access to AD diagnosis and disease-modifying treatments.