Neuropathologic correlates of distinct plasma biomarker profiles in community-living older adults

There has been a rapid growth in research on peripheral fluid biomarkers for Alzheimer’s Disease and Alzheimer’s Disease related dementias (AD/ADRD) because they are non-invasive, relatively inexpensive, and easily accessible. The most commonly used plasma biomarkers include β-amyloid (Aβ), phosphorylated tau (p-tau), neurofilament light chain (NfL), and glial fibrillary acidic protein (GFAP). The extent to which distinct profiles of multiple plasma biomarkers correlate with common neuropathologies is unclear. Using clinicopathologic data from 405 community-dwelling older adults, we applied latent profile analysis on 4 plasma biomarkers, i.e., Aβ42/40 ratio, p-tau217, NfL and GFAP, and examined the correlates of the latent profiles with 4 degeneration measures of AD, Lewy bodies, limbic-predominant age-related TDP-43 encephalopathy (LATE), hippocampal sclerosis, and 5 vascular measures including chronic macroscopic infarcts, microinfarcts, cerebral amyloid angiopathy, atherosclerosis and arteriosclerosis. On average, participants died at the age of 89 and blood samples for plasma biomarkers were measured 3.9 years before death. Over 75% were female and 24% were non-Latino Black. We observed 3 distinct biomarker profiles. Profile #1, characterized by low p-tau217, low GFAP, low NfL and high Aβ42/40, represents most participants (55.6%) with better than average biomarker levels. Both Profile #2 and Profile #3 showed worse than average biomarker levels. Profile #2, representing 34.8% of the participants, was high in p-tau217 and GFAP. By contrast, Profile #3, representing 9.6% of the participants, was high in NfL and GFAP. Examination of neuropathologic correlates of these plasma biomarker profiles revealed that Profile #2 exemplifies older adults with a high burden of neurodegeneration; almost all participants (92.9%) in Profile #2 had a diagnosis of pathologic AD, and the group also had the highest percentage of participants with Lewy bodies (41.1%). In comparison, Profile #3 exemplifies older adults with more severe vascular conditions; participants in this group had the highest percentage of macroscopic infarcts (31.6%) and moderate or severe atherosclerosis (42.1%). Together, these findings suggest that common plasma biomarkers may exhibit profiles reflective of distinct pathophysiologic processes.