Some biomarkers of Alzheimer disease (AD) may reveal earlier stages of disease, a new study suggests.
Tau pathology in cerebrospinal fluid (CSF) and positron emission tomography (PET) was assessed from a cohort of 322 participants in the Alzheimer’s Disease Neuroimaging Initiative. Patients were either cognitively unimpaired (CU) (n=213), had mild cognitive impairment (MCI) (n=98), or had AD dementia (n=11).
Clinically relevant thresholds for CSF phosphorylated tau (P-tau) (≥26.64 pg/mL) and flortaucipir-PET meta-regions of interest (ROI) (standard uptake value ratio -1.37) indicated participants’ tau status as CSF-/PET- (n=210), CSF+/PET- (n=63), CSF-/PET+ (n=15), and CSF+/PET+ (n=34).
Comparisons were made between tau-positive and tau-negative groups, demographic and clinical variables, amyloid β-PET burden, and flortaucipir-PET binding across Braak stage-related ROIs. Rates of tau accumulation in CSF and cognitive decline were also compared.
One-third of participants had abnormal CSF tau or were tau positive on both CSF assay and PET.
Tau-positive individuals showed increased amyloid β-PET burden. Tau-positive individuals had a history of accelerated CSF tau accrual, but only persons with tau-PET abnormality showed a similar significant decline in cognition.
The authors concluded that elevation of CSF P-tau appears to precede flortaucipir-PET detection and may occur before measurable cognitive decline.