Informing etiological heterogeneity of mild cognitive impairment and risk for progression to dementia with plasma p-tau217.

backgroundMild cognitive impairment (MCI) is a clinical diagnosis representing early symptom changes with preserved functional independence. There are multiple potential etiologies of MCI. While often presumed to be related to Alzheimer's disease (AD), other neurodegenerative and non-neurodegenerative causes are common. Wider availability of relatively non-invasive plasma AD biomarkers, such as p-tau217, can provide invaluable insights into MCI clinico-pathology and the associated implications for symptom etiology, prognosis (e.g., risk for progression to dementia), and treatment options.

objectivesThe main goal of this study was to evaluate differences between individuals with MCI with and without plasma p-tau217 biomarker evidence of AD (MCI

designWe conducted an observational cross-sectional and longitudinal clinical research study. Study groups were compared cross-sectionally on demographics, recruitment, clinical measures, and biomarkers (chi square analyses, analyses of covariance). Contributors to functional changes were evaluated with multiple linear regression. Factors associated with the odds of progression from MCI to dementia longitudinally were evaluated with binary logistic regression.

setting1Florida Alzheimer's Disease Research Center.

participantsCross-sectional analyses included 378 older adults classified as CN MEASUREMENTS: Demographics (age, sex, years of education, self-identified race and ethnicity, primary spoken language), National Alzheimer's Coordinating Center-defined clinical phenotypes (Clinically Normal, Impaired - Not MCI, Amnestic MCI, Nonamnestic MCI, Dementia), recruitment source (clinic-based versus community-based), genetics (APOE genotype), functional evaluation (Clinical Dementia Rating scale), global cognition (Mini Mental State Exam), vascular history (Vascular Burden Score), neuropsychiatric symptoms (NPI-Q Total score), plasma biomarkers (ALZPath p-tau217, Quanterix Simoa-based GFAP and NfL), and brain imaging (grey matter volume in select AD-relevant regions of interest, global white matter hyperintensity volume).

resultsAmong those with MCI, 104 (34.4%) had plasma biomarker evidence of AD. MCI

conclusionsMCI is etiologically heterogeneous. The presence of Alzheimer's pathology defined by elevated plasma p-tau217 in individuals with MCI significantly worsens prognosis. Neuropsychiatric symptoms may contribute to cognitive complaints and risk for progressive decline irrespective of AD pathology. Plasma p-tau217 can inform our understanding of base rates of different MCI phenotypes on a larger scale. As with other AD biomarkers, frequency of elevated plasma p-tau217 and odds of progression to dementia requires careful consideration of recruitment source (clinic- vs. community-based), especially across ethno-racially diverse older adults. Ongoing integration of emerging neurodegenerative disease biomarkers with detailed clinical evaluations will continue to improve treatment specificity and prognosis.