Blood Biomarkers for the Diagnosis of Neurodegenerative Dementia: A Systematic Review

Examining the relationship between plasma pTau181 and cognitive decline, structural brain integrity, and biological ageing in midlife

INTRODUCTION

Although plasma pTau181 has been shown to accurately discriminate patients with Alzheimer's disease from healthy older adults, its utility as a preclinical biomarker in middle-aged community-based cohorts is unclear.

METHODS

Participants were members of the Dunedin Multidisciplinary Health and Development Study, a longitudinal study of 1037 people born in New Zealand in 1972-1973. Plasma pTau181, MRI-based brain structure, and DunedinPACE (an epigenetic biomarker of biological ageing) were measured at age 45; cognition was measured in childhood and age 45.

RESULTS

We observed a wide range of pTau181 concentrations in our same-aged sample (n=856; M=13.6pg/mL, SD=9.1pg/mL). Males had significantly higher pTau181 concentrations than females. No statistically significant associations were observed with cognitive decline, lower structural brain integrity, or accelerated biological ageing.

DISCUSSION

In this midlife cohort, wide variation in pTau181 concentrations was present by age 45, but was not associated with patterns of AD-risk in cognition, brain structure, or biological ageing.

Alzheimer's disease blood-based biomarker testing: A stakeholder-informed assessment of coverage considerations

BackgroundRecently published clinical studies suggest that blood-based biomarker tests (BBMTs) for Alzheimer's disease (AD) provide value, but in the U.S., neither public nor private payers currently cover these tests.ObjectiveTo describe considerations for payer coverage of AD BBMTs that would need to be addressed to facilitate timely diagnosis and equitable patient access if clinical utility is demonstrated.MethodsWe performed a targeted literature review to characterize predictable coverage barriers for BBMTs and inform the development of an interview guide. We conducted semi-structured interviews with clinicians, researchers, test developers, and a patient advocate and former payer (N = 12) to assess the barriers and refine the proposed key considerations for obtaining payer coverage.ResultsStakeholders noted that payers will require evidence of clinical validity and utility of BBMTs as part of their coverage determinations contingent on the specific indication for testing, with insufficient evidence for screening applications currently. Stakeholders also agreed that there are evidence gaps for use of BBMTs in patients from ethnic and racial minority communities that must be addressed. Given the shortage of memory specialists, stakeholders noted that limiting testing coverage authorization to specialists could be harmful to patients, particularly the underserved. Interviewees also agreed that patients with mild cognitive impairment or early-stage AD could benefit from earlier diagnosis to avoid progressing to moderate disease and limiting eligibility for new disease-modifying therapies.ConclusionsIf BBMTs meet criteria for clinical utility, anticipating and planning for coverage and reimbursement before widespread implementation will be critical to ensuring broad, equitable access to BBMTs.

Diagnostic journey and management of patients with mild cognitive impairment and Alzheimer's disease dementia: A multinational, real-world survey

BackgroundAn Alzheimer's disease (AD) diagnosis made in the earliest symptomatic stages substantially benefits patients and their care partners. However, little is known regarding the clinical, healthcare system-level, and patient-specific barriers that hinder timely diagnosis and treatment.ObjectiveTo explore real-world practices surrounding the diagnostic journey and management of mild cognitive impairment (MCI)/AD dementia patients.MethodsData were drawn from Adelphi Real World Dementia Disease Specific Programme™, a cross-sectional survey of physicians treating MCI/AD dementia patients in France, Germany, Italy, Spain, the United Kingdom, the United States, and Japan between 2022 and 2024.ResultsOverall, 779 physicians reported data on 5551 patients. Physicians indicated current disease severity for 5421 patients; 37.2% had MCI (87.3% with suspected prodromal AD and 12.7% undetermined etiology), 17.2% AD with mild dementia, 31.1% AD with moderate dementia, and 14.5% AD with severe dementia. When not immediately diagnosed, the median time from first consultation to initial diagnosis was 8.9 and 12.6 weeks when patients first consulted and were diagnosed by either a primary care practitioner (PCP) or a specialist, respectively, compared with 21.6 weeks when a PCP referred to a specialist for diagnosis. Diagnostic delays were predominantly due to specialist wait times. Few patients had diagnostic AD biomarker tests (cerebrospinal fluid testing 9.5%, amyloid positron emission tomography 3.7%, AD-blood tests 5.3%).ConclusionsTimely MCI and AD diagnosis is impeded by referral delays and limited use of biomarker testing. Addressing these critical care gaps requires enhanced physician training, reduced wait times and increased biomarker utilization for early management.

Altered spatiotemporal brain dynamics of interoception in behavioural-variant frontotemporal dementia

BACKGROUND

Dysfunctional allostatic-interoception, altered processing of bodily signals in response to environmental demands, occurs in behavioural-variant frontotemporal dementia (bvFTD) patients. Previous research has not investigated the dynamic nature of interoception using methods like intrinsic neural timescales. We hypothesised that longer intrinsic neural timescales of interoception would occur in bvFTD patients, evidencing dysfunctional allostatic-interoception.

METHODS

One-hundred and twelve participants (31 bvFTD patients, 35 Alzheimer's disease patients, AD and 46 healthy controls) completed a well-validated task measuring cardiac-interoception and exteroception. Simultaneous EEG and ECG were recorded. Intrinsic neural timescales were measured via the autocorrelation window (ACW) of broadband EEG signals from each heartbeat and a time-lagged version of itself. Spatiotemporal clustering analyses identified clusters with significant between-group differences in each condition. Voxel-based morphometry was used to target the allostatic-interoceptive network. Neuropsychological tests of cognition and social cognition were assessed.

FINDINGS

In bvFTD patients, longer interoceptive-ACWs than controls were observed in the bilateral fronto-temporal and parietal regions. In AD patients, longer interoceptive-ACWs than controls were observed in central and occipitoparietal brain regions. No differences were observed during exteroception. In bvFTD patients only, longer interoceptive-ACW was linked to worse sociocognitive performance. Structural neural correlates of interoceptive-ACW in bvFTD involved the anterior cingulate, insula, orbitofrontal cortex, hippocampus, and angular gyrus.

INTERPRETATION

Our findings suggest a core allostatic-interoceptive deficit occurs in people with bvFTD. Further, altered interoceptive intrinsic neural timescales may provide a neurobiological mechanism underpinning the complex behaviours observed in bvFTD patients. Our findings support synergistic models of brain disease and can inform clinical practice.

FUNDING

All funding sources are reported in the Acknowledgements.

Application of the Trend of miRNA Expression Levels in APP/PS1 Mice Plasma for the Early Diagnosis of Alzheimer's Disease

Alzheimer's disease (AD) is the most common form of dementia and seriously affects people's quality of life. In recent years, many circulating microRNAs (miRNAs) have been reported as potential diagnostic biomarkers for AD. However, there are no reliable miRNAs for early diagnosis of AD because miRNAs are dynamically changing during the disease process. The present study was to seek reliable biomarkers for early diagnosis of AD by detecting changes in miRNAs in plasma from young APPswe/PS1Δ9 double-transgenic mice (APP/PS1 mice) using a quantitative real-time PCR (qRT-PCR) method. Some behavioral experiments and pathological tests were used to characterize the progress of AD in APP/PS1 transgenic mice. The results showed that the expression levels of several plasma miRNAs targeting BACE1 and APP showed consistent trends in the early stages of APP/PS1 mice. The expression levels of miR-34a-5p, miR-29c-3p, miR-107-3p, and miR-101a-3p in the plasma of APP/PS1 female mice decreased with cognitive decline, demonstrating their potential as biomarkers for early diagnosis of female AD patients. The expression levels of these miRNAs fluctuated significantly in APP/PS1 male mice, and the reason for this difference may be related to the biological sex differences in AD. This fluctuation may serve as an indicative risk signal for the early stage of AD in male patients.

Integrated bioinformatics and experimental analysis of CHAF1B as a novel biomarker and immunotherapy target in LUAD

The prognosis and treatment efficacy of lung adenocarcinoma (LUAD), a disease with a high incidence, remains unsatisfactory. Identifying new biomarkers and therapeutic targets for LUAD is essential. Chromosomal assembly factor 1B (CHAF1B), a p60 component of the CAF-1 complex, is closely linked to tumor incidence and cell proliferation. However, CHAF1B's biological role and molecular mechanism in LUAD remain unclear. Here, CHAF1B expression in LUAD was examined using the GEPIA2 and UALCAN databases. Using The Cancer Genome Atlas (TCGA) LUAD database, we analyzed the diagnostic and prognostic significance of CHAF1B and its association with immune infiltration and immunological checkpoints. Gene ontology (GO) enrichment and single-cell function analyses were employed to investigate CHAF1B's possible biological roles. Drug sensitivity analysis predicted CHAF1B's effect on chemotherapeutic drug sensitivity. We also predicted lncRNAs-miRNA-CHAF1B axis to explore the molecular mechanism of CHAF1B in LUAD. Preliminary in vitro studies using qRT-PCR, CCK8, Transwell, glucose, and lactate metabolism confirmed CHAF1B's expression and role in LUAD. Its expression is associated with drug sensitivity, immunological checkpoints, and immune cell infiltration. We predicted that three miRNAs (miR-29c-3p, miR-145-5p, miR-1247-5p) and three lncRNAs (AL139287.1, NEAT1, SHG1) may be target miRNAs and target lncRNAs that regulate CHAF1B. In vitro tests showed that CHAF1B suppression decreased LUAD's migration, invasion, proliferation, and glycolysis. Overall, CHAF1B may be an innovative biomarker and therapeutic target for LUAD.

Blood-Based Biomarkers in Frontotemporal Dementia: A Narrative Review

This narrative review explores the current landscape of blood biomarkers in Frontotemporal dementia (FTD). Neurofilament light chain (NfL) may be useful in the differentiation of behavioral variant FTD from primary psychiatric disorders (PPDs) or dementia with Lewy bodies (DLB). In prodromal FTD and presymptomatic mutation carriers (GRN, MAPT, C9orf72), elevated NfL may herald pheno-conversion to full-blown dementia. Baseline NfL correlates with steeper neuroanatomical changes and cognitive, behavioral and functional decline, making NfL promising in monitoring disease progression. Phosphorylated neurofilament heavy chain (pNfH) levels have a potential limited role in the demarcation of the conversion stage to full-blown FTD. Combined NfL and pNfH measurements may allow a wider stage stratification. Total tau levels lack applicability in the framework of FTD. p-tau, on the other hand, is of potential value in the discrimination of FTD from Alzheimer's dementia. Progranulin concentrations could serve the identification of GRN mutation carriers. Glial fibrillary acidic protein (GFAP) may assist in the differentiation of PPDs from behavioral variant FTD and the detection of GRN mutation carriers (additional research is warranted). Finally, TAR DNA-binding protein-43 (TDP-43) appears to be a promising diagnostic biomarker for FTD. Its potential in distinguishing TDP-43 pathology from other FTD-related pathologies requires further research.

Plasma and CSF neurofilament light chain distinguish neurodegenerative from primary psychiatric conditions in a clinical setting

INTRODUCTION

People with neurodegenerative disorders (ND) frequently face diagnostic delay and misdiagnosis. We investigated blood and cerebrospinal fluid (CSF) neurofilament light chain (NfL) to distinguish ND from primary psychiatric disorders (PPD), a common challenge in clinical settings.

METHODS

Plasma and CSF NfL levels were measured and compared between groups, adjusting for age, sex, and weight.

RESULTS

A total of 337 participants were included: 136 ND, 77 PPD, and 124 Controls. Plasma NfL was 2.5-fold elevated in ND compared to PPD and had strong diagnostic performance (area under the curve, [AUC]: 0.86, 81%/85% specificity/sensitivity) that was comparable to CSF NfL (2-fold elevated, AUC: 0.89, 95%/71% specificity/sensitivity). Diagnostic performance was especially strong in younger people (40- < 60 years). Additional findings were cutoffs optimized for sensitivity and specificity, and issues important for future clinical translation.

CONCLUSIONS

This study adds important evidence for a simple blood-based biomarker to assist as a screening test for neurodegeneration and distinction from PPD, in clinical settings.

HIGHLIGHTS

NfL levels were significantly higher in ND versus PPD. Plasma NfL showed strong diagnostic performance, comparable to CSF NfL, to distinguish ND from PPD. Diagnostic performance was higher in younger people, where diagnostic challenges are greater. Further research is needed on analytical and reference range factors, for clinical translation. These findings support a simple screening blood test for neurodegeneration.

A New Strategy for Ultrasensitive Detection Based on Target microRNA-Triggered Rolling Circle Amplification in the Early Diagnosis of Alzheimer's Disease

There is an urgent need to accurately quantify microRNA (miRNA)-based Alzheimer's disease (AD) biomarkers, which have emerged as promising diagnostic biomarkers. In this study, we present a rapid and universal approach to establishing a target miRNA-triggered rolling circle amplification (RCA) detection strategy, which achieves ultrasensitive detection of several targets, including miR-let7a-5p, miR-34a-5p, miR-206-3p, miR-9-5p, miR-132-3p, miR-146a-5p, and miR-21-5p. Herein, the padlock probe contains three repeated signal strand binding regions and a target miRNA-specific region. The target miRNA-specific region captures miRNA, and then the padlock probe is circularized with the addition of T4 DNA ligase. Subsequently, an RCA reaction is triggered, and RCA products containing multiple signal strand binding regions are generated to trap abundant fluorescein-labeled signal strands. The addition of exonuclease III (Exo III) causes signal strand digestion and leads to RCA product recycling and liberation of fluorescein. Ultimately, graphene oxide (GO) does not absorb the liberated fluorescein because of poor mutual interaction. This method exhibited high specificity, sensitivity, repeatability, and stability toward let-7a, with a detection limit of 19.35 fM and a linear range of 50 fM to 5 nM. Moreover, it showed excellent applicability for recovering miRNAs in normal human serum. Our strategy was applied to detect miRNAs in the plasma of APP/PS1 mice, demonstrating its potential in the diagnosis of miRNA-associated disease and biochemical research.

How close are we to a breakthrough? The hunt for blood biomarkers in Parkinson's disease diagnosis

Parkinson's disease (PD), being the second largest neurodegenerative disease, poses challenges in early detection, resulting in a lack of timely treatment options to effectively manage the disease. By the time clinical diagnosis becomes possible, more than 60% of dopamine neurons in the substantia nigra (SN) of patients have already degenerated. Therefore, early diagnosis or identification of warning signs is crucial for the prompt and timely beginning of the treatment. However, conducting invasive or complex diagnostic procedures on asymptomatic patients can be challenging, making routine blood tests a more feasible approach in such cases. Numerous studies have been conducted over an extended period to search for effective diagnostic biomarkers in blood samples. However, thus far, no highly effective biomarkers have been confirmed. Besides classical proteins like α-synuclein (α-syn), phosphorylated α-syn and oligomeric α-syn, other molecules involved in disease progression should also be given equal attention. In this review, we will not only discuss proposed biomarkers that are currently under investigation but also delve into the mechanisms underlying the disease, focusing on processes such as α-syn misfolding, intercellular transmission and the crossing of the blood-brain barrier (BBB). Our aim is to provide an updated overview of molecules based on these processes that may potentially serve as blood biomarkers.

Improved Accuracy of the Addenbrooke's Cognitive Examination-Revised in the Diagnosis of Mild Cognitive Impairment, Mild Dementia Due to Alzheimer's Disease and Behavioral Variant Frontotemporal Dementia Using Mokken Scale Analysis

Background

The Addenbrooke's Cognitive Examination-Revised (ACE-R) is an accessible cognitive tool that supports the early detection of mild cognitive impairment (MCI), Alzheimer's disease (AD), and behavioral variant frontotemporal dementia (bvFTD).

Objective

To investigate the diagnostic efficacy of the ACE-R in MCI, AD, and bvFTD through the identification of novel coefficients for differentiation between these diseases.

Methods

We assessed 387 individuals: 102 mild AD, 37 mild bvFTD, 87 with amnestic MCI patients, and 161 cognitively unimpaired controls. The Mokken scaling technique facilitated the extraction out of the 26 ACE-R items that exhibited a common latent trait, thereby generating the Mokken scales for the AD group and the MCI group. Subsequently, we performed logistic regression, integrating each Mokken scales with sociodemographic factors, to differentiate between AD and bvFTD, as well as between AD or MCI and control groups. Ultimately, the Receiver Operating Characteristic curve analysis was employed to assess the efficacy of the coefficient's discrimination.

Results

The AD-specific Mokken scale (AD-MokACE-R) versus bvFTD exhibited an Area Under the Curve (AUC) of 0.922 (88% sensitivity and specificity). The AD-MokACE-R versus controls achieved an AUC of 0.968 (93% sensitivity, 94% specificity). The MCI-specific scale (MCI-MokACE-R) versus controls demonstrated an AUC of 0.859 (78% sensitivity, 79% specificity).

Conclusions

The ACE-R's capacity is enhanced through statistical methods and demographic integration, allowing for accurate differentiation between AD and bvFTD, as well as between MCI and controls. This new method not only reinforces its clinical value in early diagnosis but also surpasses traditional approaches noted in prior studies.

Extracellular Vesicles in Domestic Animals: Cellular Communication in Health and Disease

Apoptotic and healthy cells of domestic animals release membrane-enclosed particles from their plasma membrane. These special structures, called extracellular vesicles, play an important role in intercellular communication. In the past, it was believed that their function was mainly to dispose unwanted cell contents and to help maintain cell homeostasis. However, we now know that they have important roles in health and disease and have diagnostic value as well as great potential for therapy in veterinary medicine. Extracellular vesicles facilitate cellular exchanges by delivering functional cargo molecules to nearby or distant tissues. They are produced by various cell types and are found in all body fluids. Their cargo reflects the state of the releasing parent cell, and despite their small size, this cargo is extraordinarily complex. Numerous different types of molecules contained in vesicles make them an extremely promising tool in the field of regenerative veterinary medicine. To further increase research interest and discover their full potential, some of the basic biological mechanisms behind their function need to be better understood. Only then will we be able to maximize the clinical relevance for targeted diagnostic and therapeutic purposes in various domestic animal species.