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Plasma biomarkers are emerging as a way to detect Alzheimer disease (AD). Researchers in this study analyzed whether plasma biomarkers for amyloid, tau, and axonal injury predicted brain amyloidosis among community-dwelling Black and non-Hispanic white (NHW) older adults matched by age, apolipoproteinE-ℇ4 (apoE-ℇ4) carrier status, and cognitive status. Plasma biomarkers included amyloid-β (Aβ42, Aβ40, and Aβ42/40), phosphorylated-tau 181 (p-tau181), phosphorylated-tau 231 (p-tau231), and neurofilament light chain (NfL). Cerebrospinal fluid (CSF) biomarkers included Aβ42, Aβ40, and Aβ42/40; p-tau181; and total tau (t-tau). A subset of participants had amyloid positron emission tomography (PET) data. The presence of brain amyloidosis was determined by set cutoff points for CSF Aβ42/40 and amyloid PET.
The Black and NHW groups each had 76 participants from the St. Louis, MO, area (median age, 68 years; 42% with at least one apoE-ℇ4 allele; 9% cognitively impaired). The Black group had lower levels of brain amyloidosis based on CSF and amyloid PET data. Plasma Aβ42/40 had the highest correlation with brain amyloidosis based on CSF and amyloid PET data in adjusted models, and plasma Aβ42/40 was significantly better than plasma tau and NfL in predicting CSF Aβ42/40 positivity. Black race was associated with a lower probability of brain amyloidosis with CSF Aβ42/40 or amyloid PET positivity in models based on plasma tau or NfL (odds ratio range, 0.27–0.31) but not in models based on plasma Aβ42/40 levels.
Schindler SE et al. Effect of race on prediction of brain amyloidosis by plasma Aβ42/Aβ40, phosphorylated tau, and neurofilament light. Neurology 2022 Apr 22; [e-pub]. (https://doi.org/10.1212/WNL.0000000000200358)
Comment
These findings show that race may affect the ability of plasma biomarkers to predict brain amyloidosis. Plasma Aβ42/40 best predicted brain amyloidosis for both Black and NHW people, but plasma tau did not have the same effect in Black people. A strength of the study is that it included a large sample size of community-dwelling older Black adults, although it was only in one Midwestern metropolitan area. Whether and how other races, including Asians, affect the ability of plasma biomarkers to predict brain amyloidosis also requires further study.