Algeciras‐Schimnich, Alicia

Abstract INTRODUCTION Plasma p‐tau217 and p‐tau217/Aβ42 reliably identify non‐Hispanic White individuals with symptomatic and pre‐clinical AD. However, performance across ethnoracially diverse groups remains unknown. METHODS Cognitively normal Black, Hispanic, and non‐Hispanic White participants completed cognitive evaluations, brain magnetic resonance imaging (MRI), amyloid and tau positron emission tomography (PET), and measures of kidney function. Plasma p‐tau217 and Aβ42 were measured using Fujirebio Lumipulse assays. Pre‐clinical AD detection was evaluated using symptomatic and cohort‐derived optimized cutoffs. RESULTS Among 191 participants (57 Black, 46 Hispanic White, 88 non‐Hispanic White), age‐adjusted plasma p‐tau217 and p‐tau217/Aβ42 performed similarly in detecting amyloid‐positive individuals (≥ 25 Centiloids), regardless of race/ethnicity. Both measures independently correlated with amyloid deposition, whereas estimated glomerular filtration rate (eGFR) correlated solely with p‐tau217. Pre‐clinical AD optimized cutoffs (p‐tau217 ≥ 0.132 pg/ml; p‐tau217/Aβ42 ≥ 0.0059) outperformed cutoffs established in symptomatic individuals (sensitivity: 83% vs. 57%; 77% vs. 63%; negative predictive value [NPV] > 93%). DISCUSSION Plasma biomarkers performed similarly across ethnoracially diverse cohorts. Optimized cutoffs may improve early detection and trial enrollment.

Abstract Background Alzheimer’s disease (AD) is clinicopathologically heterogeneous. A proportion of patients living with AD present clinically at a younger onset of cognitive symptoms before 65 years old and/or non-amnestic clinical syndromes. Neuropathologically, corticolimbic distribution of neurofibrillary tangle pathology occurs on a continuum with some cases having greater cortical tau pathology relative to limbic regions and others with relatively restricted accumulation in limbic structures. These patterns of corticolimbic tangle distribution are associated with clinical presentation and age at onset. This study sought to examine protein expression differences across the spectrum of clinicopathologic heterogeneity using the NULISA targeted proteomics platform. Methods A series of thirteen neuropathologically diagnosed AD cases from Mayo Clinic prospectively followed research studies were selected to reflect heterogeneity of clinical syndromes and corticolimbic distribution of tangle pathology. Frozen postmortem brain tissue samples were isolated from inferior parietal cortex and homogenized in RIPA buffer for analysis using Alamar Biosciences’ NULISA CNS disease 120 panel. Applying a conservative detection threshold of 75% level of detection for the novel application of NULISA in human brain, we evaluated levels of 69 of 129 protein targets across samples. We examined associations between age at onset cognitive symptoms and corticolimbic distribution of tangles (CLix) separately with individual protein targets using linear regression analysis. Results AD cases with a younger age at onset had higher measured levels of ubiquitin, while older age was associated with higher levels of total tau, CRH, and NPTX2. Investigations of corticolimbic heterogeneity revealed AD cases with lower CLix score (i.e., cortical predominant distribution of tau) had higher measured p-tau181, p-tau231, ubiquitin, and p62. AD cases with higher CLix (i.e., relative cortical sparing) had higher levels of total tau, CRH, NPTX2, MDH1, and HBA1. Brain-derived total tau consistently showed a stronger association in both models. Conclusion This work demonstrates the utility of postmortem proteomics for investigating biomarkers associated with AD clinicopathologic heterogeneity. We observed proteomic differences in synapse integrity, tau post-translational modification, and ubiquitination associated with age at symptomatic onset and corticolimbic distribution of tangle pathology.

This cross-sectional study evaluates the performance of the US Food and Drug Administration–cleared phosphorylated tau 217 (p-tau217) to β-amyloid 42 ratio cut points used to detect amyloid pathology associated with Alzheimer disease.

Abstract INTRODUCTION We examined when Alzheimer's disease biomarkers become informative by identifying age‐related breakpoints with slope‐changing trajectories. METHODS In 2082 Mayo Clinic Study of Aging participants, we modeled plasma amyloid beta (Aβ)42/40, phosphorylated tau (p‐tau)181, glial fibrillary acidic protein (GFAP), neurofilament light chain (NfL), amyloid/tau positron emission tomography (PET), hippocampal volume (HVa), and global cognition. Generalized additive models described age trends; Davies' test and piecewise linear regression estimated breakpoints. A C2N subsample ( n = 462) provided mass‐spectrometry plasma markers (p‐tau181, p‐tau217, their ratios, Aβ42/40). RESULTS In the full cohort, Aβ42/40, HVa, and cognition declined with age; p‐tau181, NfL, GFAP, and amyloid/tau PET increased. We observed single breakpoints (years, 95% CI): GFAP 68.1 (63.5–71.8), NfL 70.7 (65.9–75.6), p‐tau181 67.2 (60.3–70.3), amyloid PET 62.3 (56.2–69.3), HVa 68.1 (63.1–71.9), cognition 59.8 (55.4–66.0); tau PET showed none. In the mass‐spectrometry subset, p‐tau217 and p‐tau181 broke at 72.6; their ratios and Aβ42/40 showed no breakpoints. DISCUSSION Breakpoints cluster near late midlife, suggesting windows for screening and monitoring.

Abstract Advances in biomarker technology, digital cognitive assessments, and amyloid‐targeting therapies have redefined the opportunities for accurate and early diagnosis and care of Alzheimer's disease (AD). These advances also create new possibilities for intervention before the onset of cognitive impairment. This paradigm shift has increased the focus on Stages 1 and 2 of AD, in which individuals are cognitively unimpaired but exhibit biological evidence of disease. While early identification of AD offers an opportunity to intervene early to delay progression and preserve quality of life, it also presents complex challenges related to communicating diagnostic results to patients and their families, contextualizing the cost effectiveness of early diagnosis and treatment, and implementation of and equitable access to treatments. Recent, successfully enrolled, preclinical AD trials highlight the complex strategies required to identify asymptomatic, biomarker‐positive individuals on a large scale, and demonstrate critical knowledge gaps in inclusion, follow‐up, and long‐term outcome measurement. The Spring 2025 Alzheimer's Association Research Roundtable (AARR) meeting brought together academics, clinicians, industry, and regulatory leaders to exchange perspectives on current challenges, key learnings, and potential strategies for identifying and treating individuals in very early stages of AD, effectively and safely. This paper presents key takeaways from the Spring 2025 AARR meeting. Highlights New criteria for Alzheimer's disease (AD) enable early identification of AD pathology. Blood tests and digital cognitive assessment tools may facilitate early and personalized care. Plasma biomarkers may be scalable in clinical settings but need confirmation or follow‐up assessments in those individuals with equivocal results. Early therapy shows best results in people with lower initial amyloid and tau burden.

Abstract INTRODUCTION Determining apolipoprotein E ( APOE ) ε4 allele status, a key genetic risk factor for Alzheimer's disease (AD), requires molecular genotyping infrastructure not widely accessible beyond specialized centers. METHODS A fully automated high‐throughput apoE E4 proteotyping immunoassay was evaluated for clinical performance (460 participants across three cohorts) and analytical validity. Concordance with polymerase chain reaction (PCR)‐based genotyping and measures of analytical validity were reported. RESULTS The apoE E4 immunoassay demonstrated 99.6% (95% confidence interval [CI]: 98.4% to 99.9%) concordance with PCR‐based APOE ε4 genotype results across the pooled clinical cohort; 100.0% (95% CI: 97.1% to 100.0%) in those with AD ( N = 127) and 99.4% (95% CI: 97.8% to 99.8%) in those without AD (333). The assay met analytical validity criteria for E4 isoform specificity, interference, precision, and stability. DISCUSSION The apoE E4 immunoassay demonstrated high concordance with PCR‐based genotyping and robust analytical validity, offering an accessible alternative for APOE ε4 zygosity assessment. Highlights A novel high‐throughput plasma‐based proteotyping immunoassay for APOE ε4 zygosity classification was developed and evaluated for clinical performance and analytical validity. The apoE E4 immunoassay demonstrated high concordance (99.6%) with PCR‐based APOE ε4 genotyping across a diverse international cohort, and a robust analytical profile. An apoE E4 immunoassay may offer a more cost‐effective and accessible alternative to DNA genotyping approaches currently used for AD risk evaluation and anti‐amyloid treatment decisions.

Abstract Associations of Alzheimer’s disease biomarker progression with cognitive decline are important to inform patient prognosis. Of particular interest is how newly available plasma biomarkers evolve relative to cognitive decline. The goals of this work are to measure how much earlier versus later an individual’s progression on plasma and PET Alzheimer’s disease biomarkers is associated with earlier versus later cognitive progression and to estimate the average timeline of progression of these processes in the population. In this cohort study of 2369 Mayo Clinic Study of Aging (MCSA) and 1591 Alzheimer’s Disease Neuroimaging Initiative (ADNI) participants, we fit non-linear mixed-effects models to estimate how much earlier versus later each individual progresses on plasma phosphorylated tau (p-tau)217, amyloid PET, tau PET and auditory verbal learning test (AVLT) sum of trials relative to the population mean (individual adjustment), the associations of these individual adjustments among biomarker pairs and how covariates affect the timing of biomarker progression. The association of individual adjustments implies mechanistic associations and the amount of variability in cognitive decline accounted for by each biomarker. By applying cut-off points, we also estimated the relative timing that these biomarkers become abnormal in the population. Associations of individual adjustments were moderate between all biomarkers and AVLT (R = 0.38–0.47) in the MCSA and stronger (R = 0.74–0.81) in ADNI; plasma p-tau217 accounted for 16% of the variability in timing of AVLT decline in the MCSA and 64% in ADNI. APOE ɛ4 carriership was associated with earlier biomarker progression. AVLT became abnormal after the biomarkers up to age 90, after which AVLT was estimated to become abnormal prior to tau biomarkers. The association of the timing of plasma and PET Alzheimer’s disease biomarker progression with cognitive decline was modest in the MCSA population-based sample and stronger in the Alzheimer’s disease-enriched ADNI cohort. The timing of plasma p-tau217 progression explained a similar degree of variability in AVLT progression as amyloid PET, supporting its utility as a marker of disease progression. The estimated temporal ordering of biomarkers and cognitive abnormality was as anticipated (amyloid, tau, cognition) up to the age of 90, beyond which AVLT was estimated to become abnormal prior to tau biomarkers, likely related to the effects of non-Alzheimer’s disease co-pathologies.

Abstract The Association for Diagnostics & Laboratory Medicine (ADLM) aims to improve health by providing education to laboratory scientists worldwide. Different regions of the world face unique challenges shaped by their national and regional contexts. However, the needs of clinical laboratories worldwide remain largely understudied. To address this gap, we conducted a comprehensive needs assessment survey among laboratory professionals in the Latin American region. The survey was distributed to over 2708 individuals across Latin American countries and yielded 148 responses. Most respondents were from urban areas (74%) and worked in private hospital laboratories (45%), with microbiology (25%) and chemistry (23%) identified as the most common specialties. Key findings include continuing education as the top challenge, identified by 59% of respondents, with a predominant preference for virtual learning formats (83%), though not exclusively; 50% also identified a preference for in-person learning. Other challenges, such as staff shortages, lack of equipment and funding, were selected by 30% to 36% of respondents, whereas regulatory oversight and quality management were less frequently identified as priorities. To contextualize the survey findings, we conducted interviews with laboratory professionals in the region. Common themes included resource and technology constraints, uneven implementation of quality standards, and the need for collaboration between government and professional organizations to bridge gaps in practice. This assessment highlights the need for targeted educational interventions to address the distinct challenges faced by Latin American laboratories. Addressing these gaps in continued education, fostering collaboration, and engaging stakeholders in the region offer a roadmap to strengthening laboratory services and health outcomes.