A Decade of Cerebrospinal Fluid Biomarkers for Alzheimer’s Disease in Belgium

Why to test for dementia: perspectives of patients, significant others and general practitioners

BACKGROUND

This study aims to provide greater insight into the current decision-making process on diagnostic testing for dementia by exploring the expectations, needs and experiences of patients with memory complaints, significant others and general practitioners (GPs).

METHODS

We performed semi-structured interviews with patients (>60 years) who consulted their GP on memory complaints, significant others and GPs. Participants were recruited until data saturation was reached in thematic analysis of interview transcripts.

RESULTS

We performed 51 interviews (patients n = 20, significant others n = 15, GPs n = 16). Thematic analysis revealed four themes: (i) 'drivers to (not) testing', i.e. need to act on symptoms, beliefs on the necessity and expected outcomes of diagnostic testing; (ii) 'patient preferences and context are critical in the actual decision', i.e. in the actual decision-making process interpretation of symptoms, GPs' desire to meet patient preferences, social context and healthcare system dynamics guided the decision; (iii) 'need for individualised communication in the decision-making process', i.e. for patients feeling heard was a prerequisite for decision-making and GPs tailored communication strategies to individual patients and (iv) 'GP practice and barriers to shared decision-making (SDM)', i.e. although GPs value SDM in the decision on diagnostic testing for dementia, patients express limited awareness of the decision and options at stake.

CONCLUSIONS

Decision-making on diagnostic testing for dementia is a multifactorial and preference-guided process for all involved stakeholders, but decisions are often not explicitly jointly made. Development of patient decision aids could facilitate better involvement and more informed choices by patients.

Proteomic comparison between non-purified cerebrospinal fluid and cerebrospinal fluid-derived extracellular vesicles from patients with Alzheimer's, Parkinson's and Lewy body dementia

Dementia is a leading cause of death worldwide, with increasing prevalence as global life expectancy increases. The most common neurodegenerative disorders are Alzheimer's disease (AD), dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD). With this study, we took an in-depth look at the proteome of the (non-purified) cerebrospinal fluid (CSF) and the CSF-derived extracellular vesicles (EVs) of AD, PD, PD-MCI (Parkinson's disease with mild cognitive impairment), PDD and DLB patients analysed by label-free mass spectrometry. This has led to the discovery of differentially expressed proteins that may be helpful for differential diagnosis. We observed a greater number of differentially expressed proteins in CSF-derived EV samples (N = 276) compared to non-purified CSF (N = 169), with minimal overlap between both datasets. This finding suggests that CSF-derived EV samples may be more suitable for the discovery phase of a biomarker study, due to the removal of more abundant proteins, resulting in a narrower dynamic range. As disease-specific markers, we selected a total of 39 biomarker candidates identified in non-purified CSF, and 37 biomarker candidates across the different diseases under investigation in the CSF-derived EV data. After further exploration and validation of these proteins, they can be used to further differentiate between the included dementias and may offer new avenues for research into more disease-specific pharmacological therapeutics.

CSF biomarker analysis of ABCA7 mutation carriers suggests altered APP processing and reduced inflammatory response

BACKGROUND

The Alzheimer's disease (AD) risk gene ABCA7 has suggested functions in lipid metabolism and the immune system. Rare premature termination codon (PTC) mutations and an expansion of a variable number of tandem repeats (VNTR) polymorphism in the gene, both likely cause a lower ABCA7 expression and hereby increased risk for AD. However, the exact mechanism of action remains unclear. By studying CSF biomarkers reflecting different types of AD-related pathological processes, we aim to get a better insight in those processes and establish a biomarker profile of mutation carriers.

METHODS

The study population consisted of 229 AD patients for whom CSF was available and ABCA7 sequencing and VNTR genotyping had been performed. This included 28 PTC mutation and 16 pathogenic expansion carriers. CSF levels of Aβ1-42, Aβ1-40, P-tau181, T-tau, sAPPα, sAPPβ, YKL-40, and hFABP were determined using ELISA and Meso Scale Discovery assays. We compared differences in levels of these biomarkers and the Aβ ratio between AD patients with or without an ABCA7 PTC mutation or expansion using linear regression on INT-transformed data with APOE-status, age and sex as covariates.

RESULTS

Carriers of ABCA7 expansion mutations had significantly lower Aβ1-42 levels (P = 0.022) compared with non-carrier patients. The effect of the presence of ABCA7 mutations on CSF levels was especially pronounced in APOE ε4-negative carriers. In addition, VNTR expansion carriers had reduced Aβ1-40 (P = 0.023), sAPPα (P = 0.047), sAPPβ (P = 0.016), and YKL-40 (P = 0.0036) levels.

CONCLUSIONS

Our results are suggestive for an effect on APP processing by repeat expansions given the changes in the amyloid-related CSF biomarkers that were found in carriers. The decrease in YKL-40 levels in expansion carriers moreover suggests that these patients potentially have a reduced inflammatory response to AD damage. Moreover, our findings suggest the existence of a mechanism, independent of lowered expression, affecting neuropathology in expansion carriers.

Utility of the Comprehensive Trail Making Test in the Assessment of Mild Cognitive Impairment in Older Patients

INTRODUCTION

The purpose of this study is to determine the usefulness of the CTMT (Comprehensive Trail Making Test) in diagnosing mild cognitive impairment in older patients. The test is used to assess executive functions, of which impairment is already observed in the early stages of the neurodegenerative process.

MATERIALS AND METHODS

The study includes 98 patients of a geriatric ward assigned to 2 groups of 49 patients each: patients diagnosed with a mild cognitive impairment and patients without a cognitive impairment, constituting the control group (group K). A set of screening tests was used in the initial study: the MMSE (Mini-Mental State Examination), MoCA (Montreal Cognitive Assessment), and CDT (Clock Drawing Test), GDS (Geriatric Depression Scale). The second study included the performance of the CTMT; the performance indicator was the time of performance.

RESULTS

Statistically significant differences are obtained between patients with mild cognitive impairments and those in cognitive normality in the performance of the CTMT test (p < 0.01). Patients with MCIs took longer to complete all trails of the test. To identify cognitive impairment, cutoff points were proposed for the CTMT total score and the other test trails. The CTMT overall score and CTMT 5 scored the highest AUCs (CTMT overall score = 0.77, CTMT Trail 5 = 0.80).

CONCLUSIONS

The Comprehensive Trail Making Test may be useful in diagnosing mild cognitive impairment as a complementary screening tool.

Association between Low Vitamin D Status, Serotonin, and Clinico-Biobehavioral Parameters in Alzheimer's Disease

INTRODUCTION

Studies suggest a role of vitamin D in the progression and symptomatology of Alzheimer's disease (AD), with few in vitro studies pointing to effects on serotonergic and amyloidogenic turnover. However, limited data exist in AD patients on the potential association with cognition and behavioral and psychological signs and symptoms of dementia (BPSD). In this retrospective cross-sectional study, we, therefore, explored potential correlations of serum 25-hydroxyvitamin D3 (25(OH)D3) concentrations, indicative of vitamin D status, with serum serotonin (5-hydroxytryptamine, 5-HT) levels, cognitive/BPSD scorings, and cerebrospinal fluid (CSF) biomarker levels.

METHODS

Frozen serum samples of 25 well-characterized AD subjects as part of a previous BPSD cohort were analyzed, of which 15 had a neuropathologically confirmed diagnosis. Serum 25(OH)D3 levels were analyzed by means of LC-MS/MS, whereas 5-HT concentrations were quantified by competitive ELISA.

RESULTS

Among AD patients, vitamin D deficiency was highly prevalent, defined as levels below 50 nmol/L. Regression analyses, adjusted for age, gender, and psychotropic medications, revealed that serum 25(OH)D3 and 5-HT levels were positively associated (p = 0.012). Furthermore, serum 25(OH)D3 concentrations correlated inversely with CSF amyloid-beta (Aβ1-42) levels (p = 0.006), and serum 5-HT levels correlated positively with aggressiveness (p = 0.001), frontal behavior (p = 0.001), depression (p = 0.004), and partly with cognitive performance (p < 0.005). Lastly, AD patients on cholinesterase inhibitors had higher serum 25(OH)D3 (p = 0.030) and lower serum 5-HT (p = 0.012) levels.

CONCLUSIONS

The molecular associations between low vitamin D status, serum 5-HT, and CSF Aβ1-42 levels are highly remarkable, warranting further mechanistic and intervention studies to disclose potential involvement in the clinico-biobehavioral pathophysiology of AD.

How far is the goal of applying β-amyloid in cerebrospinal fluid for clinical diagnosis of Alzheimer's disease with standardization of measurements?

Cerebrospinal fluid (CSF) β-amyloid (Aβ) is important for early diagnosis of Alzheimer's disease (AD). However, the cohort distributions and cut-off values have large variation across different analytical assays, kits, and laboratories. In this review, we summarize the cut-off values and diagnostic performance for CSF Aβ1-42 and Aβ1-42/Aβ1-40, and explore the important effect factors. Based on the Alzheimer's Association external quality control program (AAQC program), the peer group coefficient of variation of manual ELISA assays for CSF Aβ1-42 was unsatisfied (>20%). Fully automated platforms with better performance have recently been developed, but still not widely applied. In 2020, the certified reference material (CRM) for CSF Aβ1-42 was launched; however, the AAQC 2021-round results did not show effective improvements. Thus, further development and popularization of CRM for CSF Aβ1-42 and Aβ1-40 are urgently required. Standardizing the diagnostic procedures of AD and related status and the pre-analytical protocols of CSF samples, improving detection performance of analytical assays, and popularizing the application of fully automated platforms are also important for the establishment of uniform cut-off values. Moreover, each laboratory should verify the applicability of uniform cut-off values, and evaluate whether it is necessary to establish its own population- and assay-specific cut-off values.

Investigating Tissue-Specific Abnormalities in Alzheimer's Disease with Multi-Shell Diffusion MRI

BACKGROUND

Most studies using diffusion-weighted MRI (DW-MRI) in Alzheimer's disease (AD) have focused their analyses on white matter (WM) microstructural changes using the diffusion (kurtosis) tensor model. Although recent works have addressed some limitations of the tensor model, such as the representation of crossing fibers and partial volume effects with cerebrospinal fluid (CSF), the focus remains in modeling and analyzing the WM.

OBJECTIVE

In this work, we present a brain analysis approach for DW-MRI that disentangles multiple tissue compartments as well as micro- and macroscopic effects to investigate differences between groups of subjects in the AD continuum and controls.

METHODS

By means of the multi-tissue constrained spherical deconvolution of multi-shell DW-MRI, underlying brain tissue is modeled with a WM fiber orientation distribution function along with the contributions of gray matter (GM) and CSF to the diffusion signal. From this multi-tissue model, a set of measures capturing tissue diffusivity properties and morphology are extracted. Group differences were interrogated following fixel-, voxel-, and tensor-based morphometry approaches while including strong FWE control across multiple comparisons.

RESULTS

Abnormalities related to AD stages were detected in WM tracts including the splenium, cingulum, longitudinal fasciculi, and corticospinal tract. Changes in tissue composition were identified, particularly in the medial temporal lobe and superior longitudinal fasciculus.

CONCLUSION

This analysis framework constitutes a comprehensive approach allowing simultaneous macro and microscopic assessment of WM, GM, and CSF, from a single DW-MRI dataset.

Improved Alzheimer's Disease versus Frontotemporal Lobar Degeneration Differential Diagnosis Combining EEG and Neurochemical Biomarkers: A Pilot Study

BACKGROUND

Distinguishing between Alzheimer's disease (AD) and frontotemporal lobar degeneration (FTLD) results in poor diagnostic accuracy.

OBJECTIVE

To investigate the utility of electroencephalography (EEG)-based biomarkers in comparison and in addition to established cerebrospinal fluid (CSF) biomarkers in the AD versus FTLD differential diagnosis.

METHODS

The study cohort comprised 37 AD and 30 FTLD patients, of which 17 AD and 9 FTLD patients had definite diagnoses. All participants had CSF neurochemical (NCM) biomarker analyses (Aβ1-42, T-tau, P-tau181, and Nf-L) and underwent 19-channel resting-state EEG. From the EEG spectra, dominant frequency peaks were extracted in four regions resulting in four dominant frequencies. This produced eight features (4 NCM + 4 EEG).

RESULTS

When NCM and EEG markers were combined, the diagnostic accuracy increased significantly. In the whole group, the accuracy went up from 79% (NCM) to almost 82%, while in the definite group only, it went up from around 85% to almost 95%. Two differences in the occurrence of the dominant EEG frequency were discovered: people lacking a clear dominant peak almost all had definite AD, while people with two peaks more often had FTLD.

CONCLUSION

Combining EEG with NCM biomarkers resulted in differential diagnostic accuracies of 82% in clinically diagnosed AD and FTD patients and of 95% in patients having a definite diagnosis, which was significantly better than with EEG or NCM biomarkers alone. This suggests that NCM and EEG markers are complementary, revealing different aspects of the disease and therefore confirms again their relevance in developing additional diagnosis tools.

Genome-wide meta-analysis for Alzheimer's disease cerebrospinal fluid biomarkers

Amyloid-beta 42 (Aβ42) and phosphorylated tau (pTau) levels in cerebrospinal fluid (CSF) reflect core features of the pathogenesis of Alzheimer's disease (AD) more directly than clinical diagnosis. Initiated by the European Alzheimer & Dementia Biobank (EADB), the largest collaborative effort on genetics underlying CSF biomarkers was established, including 31 cohorts with a total of 13,116 individuals (discovery n = 8074; replication n = 5042 individuals). Besides the APOE locus, novel associations with two other well-established AD risk loci were observed; CR1 was shown a locus for Aβ42 and BIN1 for pTau. GMNC and C16orf95 were further identified as loci for pTau, of which the latter is novel. Clustering methods exploring the influence of all known AD risk loci on the CSF protein levels, revealed 4 biological categories suggesting multiple Aβ42 and pTau related biological pathways involved in the etiology of AD. In functional follow-up analyses, GMNC and C16orf95 both associated with lateral ventricular volume, implying an overlap in genetic etiology for tau levels and brain ventricular volume.

Establishment of combined diagnostic models of Alzheimer's disease in a Chinese cohort: the Chongqing Ageing & Dementia Study (CADS)

Cerebrospinal fluid (CSF) biomarkers are essential for the accurate diagnosis of Alzheimer's disease (AD), yet their measurement levels vary widely across centers and regions, leaving no uniform cutoff values to date. Diagnostic cutoff values of CSF biomarkers for AD are lacking for the Chinese population. As a member of the Alzheimer's Association Quality Control program for CSF biomarkers, we aimed to establish diagnostic models based on CSF biomarkers and risk factors for AD in a Chinese cohort. A total of 64 AD dementia patients and 105 age- and sex-matched cognitively normal (CN) controls from the Chongqing Ageing & Dementia Study cohort were included. CSF Aβ42, P-tau181, and T-tau levels were measured by ELISA. Combined biomarker models and integrative models with demographic characteristics were established by logistic regression. The cutoff values to distinguish AD from CN were 933 pg/mL for Aβ42, 48.7 pg/mL for P-tau181 and 313 pg/mL for T-tau. The AN model, including Aβ42 and T-tau, had a higher diagnostic accuracy of 89.9%. Integrating age and APOE ε4 status to AN model (the ANA'E model) increased the diagnostic accuracy to 90.5% and improved the model performance. This study established cutoff values of CSF biomarkers and optimal combined models for AD diagnosis in a Chinese cohort.

Should Doctors Offer Biomarker Testing to Those Afraid to Develop Alzheimer's Dementia? : Applying the Method of Reflective Equilibrium for a Clinical Dilemma

An increasing number of people seek medical attention for mild cognitive symptoms at older age, worried that they might develop Alzheimer's disease. Some clinical practice guidelines suggest offering biomarker testing in such cases, using a brain scan or a lumbar puncture, to improve diagnostic certainty about Alzheimer's disease and enable an earlier diagnosis. Critics, on the other hand, point out that there is no effective Alzheimer treatment available and argue that biomarker tests lack clinical validity. The debate on the ethical desirability of biomarker testing is currently polarized; advocates and opponents tend to focus on their own line of arguments. In this paper, we show how the method of reflective equilibrium (RE) can be used to systematically weigh the relevant arguments on both sides of the debate to decide whether to offer Alzheimer biomarker testing. In the tradition of RE, we reflect upon these arguments in light of their coherence with other argumentative elements, including relevant facts (e.g. on the clinical validity of the test), ethical principles, and theories on societal ideals or relevant concepts, such as autonomy. Our stance in the debate therefore rests upon previously set out in-depth arguments and reflects a wide societal perspective.

Associating Alzheimer’s disease pathology with its cerebrospinal fluid biomarkers

Alzheimer’s disease cerebrospinal fluid (CSF) biomarkers 42 amino acid long amyloid-β peptide (Aβ1-42), total tau protein (T-tau), and tau protein phosphorylated at threonine 181 (P-tau181) are considered surrogate biomarkers of Alzheimer’s disease pathology, and significantly improve diagnostic accuracy. Their ability to reflect neuropathological changes later in the disease course is not well characterized. This study aimed to assess the potential of CSF biomarkers measured in mid- to late-stage Alzheimer’s disease to reflect post mortem neuropathological changes. Individuals were selected from 2 autopsy cohorts of Alzheimer’s disease patients in Antwerp and Amsterdam. Neuropathological diagnosis was performed according to the updated consensus National Institute on Aging-Alzheimer’s Association guidelines by Montine et al, which includes quantification of amyloid beta plaque, neurofibrillary tangle, and neuritic plaque load. CSF samples were analyzed for Aβ1-42, T-tau, and P-tau181 by ELISA. 114 cases of pure definite Alzheimer’s disease were included in the study (mean age 74 years, disease duration 6 years at CSF sampling, 50% females). Median interval between CSF sampling and death was one year. We found no association between Aβ1-42 and Alzheimer’s disease neuropathological change profile. In contrast, an association of P-tau181 and T-tau with Alzheimer’s disease neuropathological change profile was observed. P-tau181 was associated with all three individual Montine scores, and the associations became stronger and more significant as the interval between lumbar puncture and death increased. T-tau was also associated with all three Montine scores, but in individuals with longer intervals from lumbar puncture to death only. Stratification of the cohort according to APOE ε4 carrier status revealed that the associations applied mostly to APOE ε4 non-carriers. Our data suggest that similarly to what has been reported for Aβ1-42, plateau levels of P-tau181 and T-tau are reached during the disease course, albeit at later disease stages, reducing the potential of tau biomarkers to monitor Alzheimer’s disease pathology as the disease progresses. As a consequence, CSF biomarkers, which are performant for clinical diagnosis of early Alzheimer’s disease, may not be well suited for staging or monitoring Alzheimer’s disease pathology as it progresses through later stages.

Sex-Specific Metabolic Pathways Were Associated with Alzheimer's Disease (AD) Endophenotypes in the European Medical Information Framework for AD Multimodal Biomarker Discovery Cohort

BACKGROUND

physiological differences between males and females could contribute to the development of Alzheimer's Disease (AD). Here, we examined metabolic pathways that may lead to precision medicine initiatives.

METHODS

We explored whether sex modifies the association of 540 plasma metabolites with AD endophenotypes including diagnosis, cerebrospinal fluid (CSF) biomarkers, brain imaging, and cognition using regression analyses for 695 participants (377 females), followed by sex-specific pathway overrepresentation analyses, APOE ε4 stratification and assessment of metabolites' discriminatory performance in AD.

RESULTS

In females with AD, vanillylmandelate (tyrosine pathway) was increased and tryptophan betaine (tryptophan pathway) was decreased. The inclusion of these two metabolites (area under curve (AUC) = 0.83, standard error (SE) = 0.029) to a baseline model (covariates + CSF biomarkers, AUC = 0.92, SE = 0.019) resulted in a significantly higher AUC of 0.96 (SE = 0.012). Kynurenate was decreased in males with AD (AUC = 0.679, SE = 0.046).

CONCLUSIONS

metabolic sex-specific differences were reported, covering neurotransmission and inflammation pathways with AD endophenotypes. Two metabolites, in pathways related to dopamine and serotonin, were associated to females, paving the way to personalised treatment.

Neurogranin as biomarker in CSF is non-specific to Alzheimer's disease dementia

We aimed to evaluate the specificity of neurogranin (Ng) for Alzheimer's disease (AD) in a dementia cohort. Cerebrospinal fluid (CSF) Ng was measured (ELISA) in two independent cohorts: (1) clinical (n = 116; age 72±11 years): AD, non-AD (+high T-tau), and controls; and (2) autopsy-confirmed (n = 97; age 71±11 years): AD and non-AD, and 50 controls (age 60±6 years). In 16 autopsy-confirmed AD and 8 control subjects, Ng was measured in tissue (BA6+BA22). Ng was compared across diagnostic groups or neuropathological staging using multilinear regression models. Median[IQR] Ng concentrations were elevated in AD (414[315-499]pg/mL) and non-AD (464[319-699]pg/mL) compared to controls (260[193-306]pg/mL), but highest in AD-high-T-tau (874[716, 1148] pg/mL) and Creutzfeldt-Jakob disease (CJD; 828[703-1373]pg/mL) in cohort 1 (p < 0.01), but not in cohort 2: AD: 358[249-470]pg/mL; non-AD:245[137-416]pg/mL; controls: 259[193-370]pg/mL. Ng and tau biomarkers strongly correlated (r = 0.4-0.9, p < 0.05), except in CJD. CSF Ng concentrations were not associated with neuropathological AD hallmarks, nor with tissue Ng concentrations. CSF Ng is a general biomarker for synaptic degeneration, strongly correlating with CSF tau, but without added value for AD differential diagnosis.

Investigation of the Molecular Role of Brain-Derived Neurotrophic Factor in Alzheimer's Disease

Brain-derived neurotrophic factor (BDNF), or abrineurin, is a member of the neurotrophin family of growth factors that acts on both the central and peripheral nervous systems. BDNF is also well known for its cardinal role in normal neural maturation. It binds to at least two receptors at the cell surface known as tyrosine kinase B (TrkB) and p75^NTR. Additional neurotrophins that are anatomically linked with BDNF include neurotrophin-3 (NT-3), neurotrophin-4 (NT-4), and nerve growth factor (NGF). It is evident that BDNF levels in patients with Alzheimer's disease (AD) are altered. AD is a progressive disorder and a form of dementia, where the mental function of an elderly person is disrupted. It is associated with a progressive decline in cognitive function, which mainly targets the thinking, memory, and behavior of the person. The degeneration of neurons occurs in the cerebral cortex region of brain. The two major sources responsible for neuronal degeneration are protein fragment amyloid-beta (Aβ), which builds up in the spaces between the nerve cells, known as plaques, disrupting the neuron signaling pathway and leading to dementia, and neurofibrillary tangles (NFTs), which are the twisted fibers of proteins that build up inside the cells. AD is highly prevalent, with recent data indicating nearly 5.8 million Americans aged 65 and older with AD in 2020, and with 80% of patients 75 and older. AD is recognized as the sixth leading cause of death in the USA, and its prevalence is predicted to increase exponentially in the coming years. As AD worsens over time, it becomes increasingly important to understand the exact pathophysiology, biomarkers, and treatment. In this article, we focus primarily on the controversial aspect of BDNF in AD, including its influence on various other proteins and enzymes and the current treatments associated with BDNF, along with future perspectives.

Serum Daytime Melatonin Levels Reflect Cerebrospinal Fluid Melatonin Levels in Alzheimer's Disease but Are Not Correlated with Cognitive Decline

Background:

Nocturnal cerebrospinal fluid (CSF) and blood melatonin levels are altered in Alzheimer’s disease (AD). However, literature remains inconclusive on daytime blood melatonin levels. A positive correlation between melatonin levels and Mini-Mental State Examination (MMSE) scores in AD subjects has been evidenced following cross-sectional analyses. Whereas a correlation between serum and spinal CSF melatonin has been shown in healthy volunteers, an equal investigation in AD patients still has to be undertaken.

Objective:

1) To evaluate whether serum melatonin levels correlate with spinal CSF melatonin levels in AD. 2) To compare daytime CSF and serum melatonin levels between patients with AD dementia, mild cognitive impairment due to AD, and healthy controls, and to evaluate whether melatonin can affect cognitive decline in AD.

Methods:

Subjects with AD and healthy controls included in two existing cohorts, of whom a CSF and serum sample was available at the neurobiobank and had at least 6 months of neuropsychological follow-up, were included in the present study. Melatonin concentrations were measured with liquid chromatography-mass spectrometry.

Results:

Daytime serum melatonin levels correlated with spinal CSF melatonin levels in AD (r = 0.751, p < 0.001). No significant differences regarding daytime melatonin levels were found between patients and controls. No correlations were observed between daytime melatonin levels and MMSE score changes.

Conclusion:

Daytime serum melatonin accurately reflects CSF melatonin levels in AD, raising the possibility to assess melatonin alterations by solely performing blood sampling if also confirmed for night-time values. However, daytime melatonin levels are not associated with changes of cognitive impairment.

Melatonin levels in the Alzheimer's disease continuum: a systematic review

Background

The search for new Alzheimer’s disease (AD) cerebrospinal fluid (CSF) and blood biomarkers with potential pathophysiological and clinical relevance continues, as new biomarkers might lead to improved early and differential diagnosis, monitoring of disease progression and might even identify new druggable targets. Melatonin might be an interesting biomarker as an inverse correlation between CSF melatonin levels, and severity of the neuropathology as measured by Braak stages has been described. Melatonin can be measured in different body fluids, such as CSF, blood, saliva and urine.

Objectives

The aim of this systematic review was to review all available studies regarding melatonin levels in different body fluids in the AD continuum and give an extensive overview of reported outcomes.

Methods

We included papers comparing melatonin levels between healthy controls and human patients belonging to the AD continuum. A systematic search of PubMed and Web of Science led to inclusion of 20 full-length English papers following exclusion of duplicates.

Results

This systematic literature search showed that disruptions in melatonin levels occur with age, but also in AD when compared to age-matched controls. Night-time melatonin levels were found to be lower in CSF and blood of AD patients as compared to controls. Literature was not conclusive regarding alterations in blood daytime melatonin levels or regarding saliva melatonin in AD patients. Decreased total and night-time melatonin production has been described in urine of AD patients.

Conclusion

Our systematic review shows evidence for disruptions in (night-time) melatonin levels in AD as compared to age-matched controls. Although more studies are needed to understand the contribution of disruption of the melatonergic system to the pathophysiology of AD, the potential anti-AD effects that have been attributed to melatonin, renders research on this topic relevant for the discovery of potential future treatment effects of melatonin for AD. The use of melatonin as potential blood biomarker for disease progression should also be further investigated.

Application of Cerebrospinal Fluid AT(N) Framework on the Diagnosis of AD and Related Cognitive Disorders in Chinese Han Population

Background

Studies concerning the impact of the AT(N) framework on diagnostic capability in the dementia population are lacking. We aimed to explore the diagnostic application of CSF AT(N) framework in clinical routines of Alzheimer's disease (AD) as well as differential diagnosis of other cognitive diseases in the Chinese Han population.

Patients and Methods

A total of 137 patients with cognitive disorders received CSF tests of Aβ₄₂, t-tau and p-tau₁₈₁. Their CSF biomarker results were categorized and interpreted by the AT(N) framework. Neurologists provided a diagnosis both pre- and post-CSF biomarker disclosure with corresponding diagnostic confidence.

Results

The total initial diagnosis included 79 patients with AD and 58 patients with non-AD (NAD). The results of CSF biomarkers led to a diagnostic change of 28% in the cohort. Approximately 81.5% (n=53) of 65 patients whose CSF biomarker showed an underlying AD pathology were finally diagnosed as AD, with an increase of 17.5% in diagnostic confidence. Thirty-seven CSF results indicating NAD pathologic changes contributed to an exclusion of AD in 56.8% (n=21) of the patients along with a modest increase of 9.8% in average confidence. Thirty-five patients with normal CSF biomarkers maintained the diagnosis of NAD in 68.6% (n=24) of the group, leading to a slight elevation of 7.6% in confidence.

Conclusion

We found that the presence of amyloid pathology (A+) is contributable to diagnosing AD and improving confidence. On occasion of negative amyloid pathology (A-), with or without tau pathology, gaining uncertainty of the primary AD diagnosis would diminish the corresponding confidence. To the best of our knowledge, this is the first study performed in the Chinese Han population with cognitive disorders that explores the clinical capability of CSF AT(N) framework in a quantitative way.

CCCDTD5: Clinical role of neuroimaging and liquid biomarkers in patients with cognitive impairment

Since 1989, four Canadian Consensus Conferences on the Diagnosis and Treatment of Dementia (CCCDTDs) have provided evidence-based dementia diagnostic and treatment guidelines for Canadian clinicians and researchers. We present the results from the Neuroimaging and Fluid Biomarkers Group of the 5th CCCDTD (CCCDTD5), which addressed topics chosen by the steering committee to reflect advances in the field and build on our previous guidelines. Recommendations on Imaging and Fluid Biomarker Use from this Conference cover a series of different fields. Prior structural imaging recommendations for both computerized tomography (CT) and magnetic resonance imaging (MRI) remain largely unchanged, but MRI is now more central to the evaluation than before, with suggested sequences described here. The use of visual rating scales for both atrophy and white matter anomalies is now included in our recommendations. Molecular imaging with [18F]-fluorodeoxyglucose ([18F]-FDG) Positron Emisson Tomography (PET) or [99mTc]-hexamethylpropyleneamine oxime/ethylene cysteinate dimer ([99mTc]-HMPAO/ECD) Single Photon Emission Tomography (SPECT), should now decidedly favor PET. The value of [18F]-FDG PET in the assessment of neurodegenerative conditions has been established with greater certainty since the previous conference, and it has now been recognized as a useful biomarker to establish the presence of neurodegeneration by a number of professional organizations around the world. Furthermore, the role of amyloid PET has been clarified and our recommendations follow those from other groups in multiple countries. SPECT with [123I]-ioflupane (DaTscanTM) is now included as a useful study in differentiating Alzheimer's disease (AD) from Lewy body disease. Finally, liquid biomarkers are in a rapid phase of development and, could lead to a revolution in the assessment AD and other neurodegenerative conditions at a reasonable cost. We hope these guidelines will be useful for clinicians, researchers, policy makers, and the lay public, to inform a current and evidence-based approach to the use of neuroimaging and liquid biomarkers in clinical dementia evaluation and management.

Neuropsychiatric Symptoms in Mild Cognitive Impairment and Dementia Due to AD: Relation With Disease Stage and Cognitive Deficits

Background: The interaction between neuropsychiatric symptoms, mild cognitive impairment (MCI), and dementia is complex and remains to be elucidated. An additive or multiplicative effect of neuropsychiatric symptoms such as apathy or depression on cognitive decline has been suggested. Unraveling these interactions may allow the development of better prevention and treatment strategies. In the absence of available treatments for neurodegeneration, a timely and adequate identification of neuropsychiatric symptom changes in cognitive decline is highly relevant and can help identify treatment targets. Methods: An existing memory clinic-based research database of 476 individuals with MCI and 978 individuals with dementia due to Alzheimer's disease (AD) was reanalyzed. Neuropsychiatric symptoms were assessed in a prospective fashion using a battery of neuropsychiatric assessment scales: Middelheim Frontality Score, Behavioral Pathology in Alzheimer's Disease Rating Scale (Behave-AD), Cohen-Mansfield Agitation Inventory, Cornell Scale for Depression in Dementia (CSDD), and Geriatric Depression Scale (30 items). We subtyped subjects suffering from dementia as mild, moderate, or severe according to their Mini-Mental State Examination (MMSE) score and compared neuropsychiatric scores across these groups. A group of 126 subjects suffering from AD with a significant cerebrovascular component was examined separately as well. We compared the prevalence, nature, and severity of neuropsychiatric symptoms between subgroups of patients with MCI and dementia due to AD in a cross-sectional analysis. Results: Affective and sleep-related symptoms are common in MCI and remain constant in prevalence and severity across dementia groups. Depressive symptoms as assessed by the CSDD further increase in severe dementia. Most other neuropsychiatric symptoms (such as agitation and activity disturbances) progress in parallel with severity of cognitive decline. There are no significant differences in neuropsychiatric symptoms when comparing "pure" AD to AD with a significant vascular component. Conclusion: Neuropsychiatric symptoms such as frontal lobe symptoms, psychosis, agitation, aggression, and activity disturbances increase as dementia progresses. Affective symptoms such as anxiety and depressive symptoms, however, are more frequent in MCI than mild dementia but otherwise remain stable throughout the cognitive spectrum, except for an increase in CSDD score in severe dementia. There is no difference in neuropsychiatric symptoms when comparing mixed dementia (defined here as AD + significant cerebrovascular disease) to pure AD.

Views on Early Diagnosis of Alzheimer's Disease Among Dutch Physicians: A Qualitative Interview Study

BACKGROUND

Hope for future treatments to prevent or slow down dementia motivates researchers to strive for ever-earlier diagnoses of Alzheimer's disease (AD) based on biomarkers, even before symptoms occur. But is a biomarker-based early diagnosis desirable in clinical practice?

OBJECTIVE

This study explores the ethical considerations that shape current clinical practice regarding early AD diagnostics and the use of biomarkers.

METHODS

In this qualitative study, Dutch physicians were interviewed. Topics included physicians' views concerning early AD diagnosis in persons with no or mild cognitive impairment, physicians' considerations regarding current and expected future practices of early AD diagnosis, the use of biomarkers, and the use of the concepts preclinical and prodromal AD. We analyzed the transcripts using directed content analysis.

RESULTS

15 general practitioners, neurologists, and geriatricians in the Netherlands were interviewed. Most of them interpreted an early AD diagnosis with an early diagnosis of dementia. We identified six clusters of considerations sometimes in favor but most often against pursuing an early AD diagnosis in people with no or mild cognitive impairment that influence physicians' diagnostic decision-making: preferences and characteristics of persons, test characteristics, impact on care, type of setting, disease concepts, and issues on a societal level.

CONCLUSION

The discussion concerning an early AD diagnosis based on biomarkers which is widely held in the scientific field, has not entered clinical practice structurally. A biomarker-based early diagnosis does not fit within Dutch physicians' views on what good care for people with no, subjective, or mild cognitive impairment should entail.

Validation of the Erlangen Score Algorithm for Differential Dementia Diagnosis in Autopsy-Confirmed Subjects

Background:

Despite decades of research on the optimization of the diagnosis of Alzheimer’s disease (AD), its biomarker-based diagnosis is being hampered by the lack of comparability of raw biomarker data. In order to overcome this limitation, the Erlangen Score (ES), among other approaches, was set up as a diagnostic-relevant interpretation algorithm.

Objective:

To validate the ES algorithm in a cohort of neuropathologically confirmed cases with AD (n = 106) and non-AD dementia (n = 57).

Methods:

Cerebrospinal fluid (CSF) biomarker concentrations of Aβ_1-42, T-tau, and P-tau₁₈₁ were measured with commercially available single analyte ELISA kits. Based on these biomarkers, ES was calculated as previously reported.

Results:

This algorithm proved to categorize AD in different degrees of likelihood, ranging from neurochemically “normal”, “improbably having AD”, “possibly having AD”, to “probably having AD”, with a diagnostic accuracy of 74% using the neuropathology as a reference.

Conclusion:

The ability of the ES to overcome the high variability of raw CSF biomarker data may provide a useful diagnostic tool for comparing neurochemical diagnoses between different labs or methods used.

Validation of Plasma Proteomic Biomarkers Relating to Brain Amyloid Burden in the EMIF-Alzheimer's Disease Multimodal Biomarker Discovery Cohort

We have previously investigated, discovered, and replicated plasma protein biomarkers for use to triage potential trials participants for PET or cerebrospinal fluid measures of Alzheimer's disease (AD) pathology. This study sought to undertake validation of these candidate plasma biomarkers in a large, multi-center sample collection. Targeted plasma analyses of 34 proteins with prior evidence for prediction of in vivo pathology were conducted in up to 1,000 samples from cognitively healthy elderly individuals, people with mild cognitive impairment, and in patients with AD-type dementia, selected from the EMIF-AD catalogue. Proteins were measured using Luminex xMAP, ELISA, and Meso Scale Discovery assays. Seven proteins replicated in their ability to predict in vivo amyloid pathology. These proteins form a biomarker panel that, along with age, could significantly discriminate between individuals with high and low amyloid pathology with an area under the curve of 0.74. The performance of this biomarker panel remained consistent when tested in apolipoprotein E ɛ4 non-carrier individuals only. This blood-based panel is biologically relevant, measurable using practical immunocapture arrays, and could significantly reduce the cost incurred to clinical trials through screen failure.

Ethical Arguments Concerning the Use of Alzheimer's Disease Biomarkers in Individuals with No or Mild Cognitive Impairment: A Systematic Review and Framework for Discussion

BACKGROUND

The shift to defining Alzheimer's disease (AD) as a biological continuum, which is characterized by the presence of biomarkers instead of clinical symptoms, has sparked a widespread debate. Insight into the given arguments and their underlying moral values is crucial to ensure well-considered and appropriate AD biomarker testing in the future.

OBJECTIVE

To critically review the arguments in favor of or against AD biomarker testing in people with no or mild cognitive impairment and to explicate their underlying moral values.

METHODS

Seven databases were systematically searched for publications mentioning arguments of interest. Arguments are identified using qualitative data-analysis and evaluated within an ethical framework.

RESULTS

Our search yielded 3,657 articles of which 34 met the inclusion criteria. We discuss the clusters of arguments separate from their evaluation and the assessment of the debate as a whole. The right to know, which derives from the moral value of respect for autonomy, is a central argument in favor of biomarker testing. On the other hand, fear of the disease and lack of a disease-modifying treatment may result in a negative balance of good over inflicted harms, which argues against its use.

CONCLUSION

Critical evaluation and weighing of the given arguments in a specific context, within an ethical framework, demonstrates the necessity to differentiate between what we hope or expect from research and where we currently stand. While AD biomarkers may have an indispensable value for research, the current advantage for clinical practice appears limited.

Added Diagnostic Value of Cerebrospinal Fluid Biomarkers for Differential Dementia Diagnosis in an Autopsy-Confirmed Cohort

Background:

Differential dementia diagnosis remains a challenge due to overlap of clinical profiles, which often results in diagnostic doubt.

Objective:

Determine the added diagnostic value of cerebrospinal fluid (CSF) biomarkers for differential dementia diagnosis as compared to autopsy-confirmed diagnosis.

Methods:

Seventy-one dementia patients with autopsy-confirmed diagnoses were included in this study. All neuropathological diagnoses were established according to standard neuropathological criteria and consisted of Alzheimer’s disease (AD) or other dementias (NONAD). CSF levels of Aβ_1 - 42, T-tau, and P-tau₁₈₁ were determined and interpreted based on the IWG-2 and NIA-AA criteria, separately. A panel of three neurologists experienced with dementia made clinical consensus dementia diagnoses. Clinical and CSF biomarker diagnoses were compared to the autopsy-confirmed diagnoses.

Results:

Forty-two patients (59%) had autopsy-confirmed AD, whereas 29 patients (41%) had autopsy-confirmed NONAD. Of the 24 patients with an ambiguous clinical dementia diagnosis, a correct diagnosis would have been established in 67% of the cases applying CSF biomarkers in the context of the IWG-2 or the NIA-AA criteria respectively.

Conclusion:

AD CSF biomarkers have an added diagnostic value in differential dementia diagnosis and can help establishing a correct dementia diagnosis in case of ambiguous clinical dementia diagnoses.

Cerebrospinal Fluid Biomarkers for Early and Differential Alzheimer's Disease Diagnosis

An accurate and early diagnosis of Alzheimer’s disease (AD) is important to select optimal patient care and is critical in current clinical trials targeting core AD neuropathological features. The past decades, much progress has been made in the development and validation of cerebrospinal fluid (CSF) biomarkers for the biochemical diagnosis of AD, including standardization and harmonization of (pre-) analytical procedures. This has resulted in three core CSF biomarkers for AD diagnostics, namely the 42 amino acid long amyloid-beta peptide (Aβ_1-42), total tau protein (T-tau), and tau phosphorylated at threonine 181 (P-tau₁₈₁). These biomarkers have been incorporated into research diagnostic criteria for AD and have an added value in the (differential) diagnosis of AD and related disorders, including mixed pathologies, atypical presentations, and in case of ambiguous clinical dementia diagnoses. The implementation of the CSF Aβ_1-42/Aβ_1-40 ratio in the core biomarker panel will improve the biomarker analytical variability, and will also improve early and differential AD diagnosis through a more accurate reflection of pathology. Numerous biomarkers are being investigated for their added value to the core AD biomarkers, aiming at the AD core pathological features like the amyloid mismetabolism, tau pathology, or synaptic or neuronal degeneration. Others aim at non-AD neurodegenerative, vascular or inflammatory hallmarks. Biomarkers are essential for an accurate identification of preclinical AD in the context of clinical trials with potentially disease-modifying drugs. Therefore, a biomarker-based early diagnosis of AD offers great opportunities for preventive treatment development in the near future.

Association of short-term cognitive decline and MCI-to-AD dementia conversion with CSF, MRI, amyloid- and 18F-FDG-PET imaging

Disease-modifying treatment trials are increasingly advanced to the prodromal or preclinical phase of Alzheimer's disease (AD), and inclusion criteria are based on biomarkers rather than clinical symptoms. Therefore, it is of great interest to determine which biomarkers should be combined to accurately predict conversion from mild cognitive impairment (MCI) to AD dementia. However, up to date, only few studies performed a complete A/T/N subject characterization using each of the CSF and imaging markers, or they only investigated long-term (≥ 2 years) prognosis. This study aimed to investigate the association between cerebrospinal fluid (CSF), magnetic resonance imaging (MRI), amyloid- and ¹⁸F-FDG positron emission tomography (PET) measures at baseline, in relation to cognitive changes and conversion to AD dementia over a short-term (12-month) period. We included 13 healthy controls, 49 MCI and 16 AD dementia patients with a clinical-based diagnosis and a complete A/T/N characterization at baseline. Global cortical amyloid-β (Aβ) burden was quantified using the ¹⁸F-AV45 standardized uptake value ratio (SUVR) with two different reference regions (cerebellar grey and subcortical white matter), whereas metabolism was assessed based on ¹⁸F-FDG SUVR. CSF measures included Aβ_1–42, Aβ_1–40, T-tau, P-tau₁₈₁, and their ratios, and MRI markers included hippocampal volumes (HV), white matter hyperintensities, and cortical grey matter volumes. Cognitive functioning was measured by MMSE and RBANS index scores. All statistical analyses were corrected for age, sex, education, and APOE ε4 genotype. As a result, faster cognitive decline was most strongly associated with hypometabolism (posterior cingulate) and smaller hippocampal volume (e.g., Δstory recall: β = +0.43 [p < 0.001] and + 0.37 [p = 0.005], resp.) at baseline. In addition, faster cognitive decline was significantly associated with higher baseline Aβ burden only if SUVR was referenced to the subcortical white matter (e.g., Δstory recall: β = −0.28 [p = 0.020]). Patients with MCI converted to AD dementia at an annual rate of 31%, which could be best predicted by combining neuropsychological testing (visuospatial construction skills) with either MRI-based HV or ¹⁸F-FDG-PET. Combining all three markers resulted in 96% specificity and 92% sensitivity. Neither amyloid-PET nor CSF biomarkers could discriminate short-term converters from non-converters.

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FDG-PET and MRI HV are the strongest predictors of cognitive decline and conversion to AD.

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Combination of visuospatial construction testing with FDG-PET or MRI HV present high predicting power of conversion.

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CSF and amyloid-PET seem less suitable markers of disease progression.

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Increased AV45-PET predicts short-term cognitive decline if SUVR is referenced to WM instead of CB.

Cerebrospinal fluid biomarkers of neurodegeneration, synaptic integrity, and astroglial activation across the clinical Alzheimer's disease spectrum

INTRODUCTION

We investigated relations between amyloid-β (Aβ) status, apolipoprotein E (APOE) ε4, and cognition, with cerebrospinal fluid markers of neurogranin (Ng), neurofilament light (NFL), YKL-40, and total tau (T-tau).

METHODS

We included 770 individuals with normal cognition, mild cognitive impairment, and Alzheimer's disease (AD)-type dementia from the EMIF-AD Multimodal Biomarker Discovery study. We tested the association of Ng, NFL, YKL-40, and T-tau with Aβ status (Aβ- vs. Aβ+), clinical diagnosis APOE ε4 carriership, baseline cognition, and change in cognition.

RESULTS

Ng and T-tau distinguished between Aβ+ from Aβ- individuals in each clinical group, whereas NFL and YKL-40 were associated with Aβ+ in nondemented individuals only. APOE ε4 carriership did not influence NFL, Ng, and YKL-40 in Aβ+ individuals. NFL was the best predictor of cognitive decline in Aβ+ individuals across the cognitive spectrum.

DISCUSSION

Axonal degeneration, synaptic dysfunction, astroglial activation, and altered tau metabolism are involved already in preclinical AD. NFL may be a useful prognostic marker.

MRI predictors of amyloid pathology: results from the EMIF-AD Multimodal Biomarker Discovery study

BACKGROUND

With the shift of research focus towards the pre-dementia stage of Alzheimer's disease (AD), there is an urgent need for reliable, non-invasive biomarkers to predict amyloid pathology. The aim of this study was to assess whether easily obtainable measures from structural MRI, combined with demographic data, cognitive data and apolipoprotein E (APOE) ε4 genotype, can be used to predict amyloid pathology using machine-learning classification.

METHODS

We examined 810 subjects with structural MRI data and amyloid markers from the European Medical Information Framework for Alzheimer's Disease Multimodal Biomarker Discovery study, including subjects with normal cognition (CN, n = 337, age 66.5 ± 7.2, 50% female, 27% amyloid positive), mild cognitive impairment (MCI, n = 375, age 69.1 ± 7.5, 53% female, 63% amyloid positive) and AD dementia (n = 98, age 67.0 ± 7.7, 48% female, 97% amyloid positive). Structural MRI scans were visually assessed and Freesurfer was used to obtain subcortical volumes, cortical thickness and surface area measures. We first assessed univariate associations between MRI measures and amyloid pathology using mixed models. Next, we developed and tested an automated classifier using demographic, cognitive, MRI and APOE ε4 information to predict amyloid pathology. A support vector machine (SVM) with nested 10-fold cross-validation was applied to identify a set of markers best discriminating between amyloid positive and amyloid negative subjects.

RESULTS

In univariate associations, amyloid pathology was associated with lower subcortical volumes and thinner cortex in AD-signature regions in CN and MCI. The multi-variable SVM classifier provided an area under the curve (AUC) of 0.81 ± 0.07 in MCI and an AUC of 0.74 ± 0.08 in CN. In CN, selected features for the classifier included APOE ε4, age, memory scores and several MRI measures such as hippocampus, amygdala and accumbens volumes and cortical thickness in temporal and parahippocampal regions. In MCI, the classifier including demographic and APOE ε4 information did not improve after additionally adding imaging measures.

CONCLUSIONS

Amyloid pathology is associated with changes in structural MRI measures in CN and MCI. An automated classifier based on clinical, imaging and APOE ε4 data can identify the presence of amyloid pathology with a moderate level of accuracy. These results could be used in clinical trials to pre-screen subjects for anti-amyloid therapies.

The EMIF-AD Multimodal Biomarker Discovery study: design, methods and cohort characteristics

BACKGROUND

There is an urgent need for novel, noninvasive biomarkers to diagnose Alzheimer's disease (AD) in the predementia stages and to predict the rate of decline. Therefore, we set up the European Medical Information Framework for Alzheimer's Disease Multimodal Biomarker Discovery (EMIF-AD MBD) study. In this report we describe the design of the study, the methods used and the characteristics of the participants.

METHODS

Participants were selected from existing prospective multicenter and single-center European studies. Inclusion criteria were having normal cognition (NC) or a diagnosis of mild cognitive impairment (MCI) or AD-type dementia at baseline, age above 50 years, known amyloid-beta (Aβ) status, availability of cognitive test results and at least two of the following materials: plasma, DNA, magnetic resonance imaging (MRI) or cerebrospinal fluid (CSF). Targeted and untargeted metabolomic and proteomic analyses were performed in plasma, and targeted and untargeted proteomics were performed in CSF. Genome-wide SNP genotyping, next-generation sequencing and methylation profiling were conducted in DNA. Visual rating and volumetric measures were assessed on MRI. Baseline characteristics were analyzed using ANOVA or chi-square, rate of decline analyzed by linear mixed modeling.

RESULTS

We included 1221 individuals (NC n = 492, MCI n = 527, AD-type dementia n = 202) with a mean age of 67.9 (SD 8.3) years. The percentage Aβ+ was 26% in the NC, 58% in the MCI, and 87% in the AD-type dementia groups. Plasma samples were available for 1189 (97%) subjects, DNA samples for 929 (76%) subjects, MRI scans for 862 (71%) subjects and CSF samples for 767 (63%) subjects. For 759 (62%) individuals, clinical follow-up data were available. In each diagnostic group, the APOE ε4 allele was more frequent amongst Aβ+ individuals (p < 0.001). Only in MCI was there a difference in baseline Mini Mental State Examination (MMSE) score between the A groups (p < 0.001). Aβ+ had a faster rate of decline on the MMSE during follow-up in the NC (p < 0.001) and MCI (p < 0.001) groups.

CONCLUSIONS

The characteristics of this large cohort of elderly subjects at various cognitive stages confirm the central roles of Aβ and APOE ε4 in AD pathogenesis. The results of the multimodal analyses will provide new insights into underlying mechanisms and facilitate the discovery of new diagnostic and prognostic AD biomarkers. All researchers can apply for access to the EMIF-AD MBD data by submitting a research proposal via the EMIF-AD Catalog.

The Cerebrospinal Fluid Aβ1-42/Aβ1-40 Ratio Improves Concordance with Amyloid-PET for Diagnosing Alzheimer's Disease in a Clinical Setting

Background:

Evidence suggests that the concordance between amyloid-PET and cerebrospinal fluid (CSF) amyloid-β (Aβ) increases when the CSF Aβ_1–42/Aβ_1–40 ratio is used as compared to CSF Aβ_1–42 levels alone.

Objective:

In order to test this hypothesis, we set up a prospective longitudinal study comparing the concordance between different amyloid biomarkers for Alzheimer’s disease (AD) in a clinical setting.

Methods:

Seventy-eight subjects (AD dementia (n = 17), mild cognitive impairment (MCI, n = 48), and cognitively healthy controls (n = 13)) underwent a [¹⁸F]Florbetapir ([¹⁸F]AV45) PET scan, [¹⁸F]FDG PET scan, MRI scan, and an extensive neuropsychological examination. In a large subset (n = 67), a lumbar puncture was performed and AD biomarkers were analyzed (Aβ_1–42, Aβ_1–40, T-tau, P-tau₁₈₁).

Results:

We detected an increased concordance in the visual and quantitative (standardized uptake value ratio (SUVR) and total volume of distribution (V_T)) [¹⁸F]AV45 PET measures when the CSF Aβ_1–42/Aβ_1–40 was applied compared to Aβ_1–42 alone. CSF biomarkers were stronger associated to [¹⁸F]AV45 PET for SUVR values when considering the total brain white matter as reference region instead of cerebellar grey matter

Conclusions:

The concordance between CSF Aβ and [¹⁸F]AV45 PET increases when the CSF Aβ_1–42/Aβ_1–40 ratio is applied. This finding is of most importance for the biomarker-based diagnosis of AD as well as for selection of subjects for clinical trials with potential disease-modifying therapies for AD.

Ratio of β-amyloid protein (Aβ) and Tau predicts the postoperative cognitive dysfunction on patients undergoing total hip/knee replacement surgery

β-amyloid (Aβ) and Tau proteins are biomarkers of Alzheimer's disease neuropathogenesis. We hypothesized that they are also potential biomarkers for postoperative cognitive dysfunction (POCD). The present study was designed to evaluate the use of the Aβ-42/Tau ratio for the diagnosis of POCD in patients undergoing hip/knee replacement surgery. A total of 80 patients who underwent total hip/knee replacement surgery were grouped into POCD or non-POCD patients at 7 days, 1 and 3 months after surgery, according to a z-score recommended by the international study of POCD. Cerebrospinal fluid samples were collected prior to surgery and the concentration of Aβ-42 and Tau protein were detected. The ratio of Aβ-42/Tau was compared between the two groups at different time points. The patients completed the whole battery of neuropsychological tests following surgery. The POCD occurrence rates at 7 days, 1 and 3 months were 40, 25 and 15%, respectively. The Aβ-42/Tau ratios were much lower in the POCD group than those in the non-POCD group at 7 days (1.7±0.4 vs. 2.6±0.3), 1 month (1.6±0.5 vs. 2.4±0.4), and 3 months (1.6±0.4 vs. 2.5±0.4). The sensitivity and specificity for diagnosis of POCD as indicated by the ratios, at the three time points, were 91.7 vs. 81.2%, 86.7 vs. 70%, and 88 vs. 75.5%, respectively. The results show the incidence of POCD of patients aged at least 65 years who have undergone hip or knee fracture surgery gradually decrease as more patients recover. However, the Aβ-42/Tau ratio can be used in forecasting the occurrence of POCD elderly patients.

Alzheimer's disease CSF biomarkers: clinical indications and rational use

This review focusses on the validation and standardization of Alzheimer's disease (AD) cerebrospinal fluid (CSF) biomarkers, as well as on the current clinical indications and rational use of CSF biomarkers in daily clinical practice. The validated AD CSF biomarkers, Aβ1-42, T-tau, and P-tau181, have an added value in the (differential) diagnosis of AD and related disorders, including mixed pathologies, atypical presentations, and in case of ambiguous clinical dementia diagnosis. CSF biomarkers should not be routinely used in the diagnostic work-up of dementia and cannot be used to diagnose non-AD dementias. In cognitively healthy subjects, CSF biomarkers can only be applied for research purposes, e.g., to identify pre-clinical AD in the context of clinical trials with potentially disease-modifying drugs. Therefore, biomarker-based early diagnosis of AD offers great opportunities for preventive treatment development in the near future.

No added diagnostic value of non-phosphorylated tau fraction (p-taurel) in CSF as a biomarker for differential dementia diagnosis

Background

The Alzheimer’s disease (AD) cerebrospinal fluid (CSF) biomarkers Aβ_1–42, t-tau, and p-tau₁₈₁ overlap with other diseases. New tau modifications or epitopes, such as the non-phosphorylated tau fraction (p-tau_rel), may improve differential dementia diagnosis. The goal of this study is to investigate if p-tau_rel can improve the diagnostic performance of the AD CSF biomarker panel for differential dementia diagnosis.

Methods

The study population consisted of 45 AD, 45 frontotemporal lobar degeneration (FTLD), 45 dementia with Lewy bodies (DLB), and 21 Creutzfeldt-Jakob disease (CJD) patients, and 20 cognitively healthy controls. A substantial subset of the patients was pathology-confirmed. CSF levels of Aβ_1–42, t-tau, p-tau₁₈₁, and p-tau_rel were determined with commercially available single-analyte enzyme-linked immunosorbent assay (ELISA) kits. Diagnostic performance was evaluated by receiver operating characteristic (ROC) curve analyses, and area under the curve (AUC) values were compared using DeLong tests.

Results

The diagnostic performance of single markers as well as biomarker ratios was determined for each pairwise comparison of different dementia groups and controls. The addition of p-tau_rel to the AD biomarker panel decreased its diagnostic performance when discriminating non-AD, FTLD, and DLB from AD. As a single marker, p-tau_rel increased the diagnostic performance for CJD. No significant difference was found in AUC values with the addition of p-tau_rel when differentiating between AD or non-AD dementias and controls.

Conclusions

The addition of p-tau_rel to the AD CSF biomarker panel failed to improve differentiation between AD and non-AD dementias.

Electronic supplementary material

The online version of this article (doi:10.1186/s13195-017-0275-5) contains supplementary material, which is available to authorized users.

Concordance between brain 18F-FDG PET and cerebrospinal fluid biomarkers in diagnosing Alzheimer's disease

OBJECTIVES

Cortical posterior hypometabolism on PET imaging with ¹⁸F-FDG (FDG-PET), and altered levels of Aß_1-42 peptide, total Tau (tTau) and phosphorylated Tau (pTau) proteins in cerebrospinal fluid (CSF) are established diagnostic biomarkers in Alzheimer's disease (AD). An evaluation has been made of the concordance and relationship between the results of FDG-PET and CSF biomarkers in symptomatic patients with suspected AD.

MATERIAL AND METHODS

A retrospective review was carried out on 120 patients with cognitive impairment referred to our Cognitive Neurology Unit, and who were evaluated by brain FDG-PET and a lumbar puncture for CSF biomarkers. In order to calculate their Kappa coefficient of concordance, the result of the FDG-PET and the set of the three CSF biomarkers in each patient was classified as normal, inconclusive, or AD-compatible. The relationship between the results of both methods was further assessed using logistic regression analysis, including the Aß_1-42, tTau and pTau levels as quantitative predictors, and the FDG-PET result as the dependent variable.

RESULTS

The weighted Kappa coefficient between FDG-PET and CSF biomarkers was 0.46 (95% CI: 0.35-0.57). Logistic regression analysis showed that the Aß_1-42 and tTau values together were capable of discriminating an FDG-PET result metabolically suggestive of AD from one non-suggestive of AD, with a 91% sensitivity and 93% specificity at the cut-off line Aß_1-42=44+1.3×tTau.

CONCLUSIONS

The level of concordance between FDG-PET and CSF biomarkers was moderate, indicating their complementary value in diagnosing AD. The Aß_1-42 and tTau levels in CSF help to predict the patient FDG-PET cortical metabolic status.

The frequency and influence of dementia risk factors in prodromal Alzheimer's disease

We investigated whether dementia risk factors were associated with prodromal Alzheimer's disease (AD) according to the International Working Group-2 and National Institute of Aging-Alzheimer's Association criteria, and with cognitive decline. A total of 1394 subjects with mild cognitive impairment from 14 different studies were classified according to these research criteria, based on cognitive performance and biomarkers. We compared the frequency of 10 risk factors between the subgroups, and used Cox-regression to examine the effect of risk factors on cognitive decline. Depression, obesity, and hypercholesterolemia occurred more often in individuals with low-AD-likelihood, compared with those with a high-AD-likelihood. Only alcohol use increased the risk of cognitive decline, regardless of AD pathology. These results suggest that traditional risk factors for AD are not associated with prodromal AD or with progression to dementia, among subjects with mild cognitive impairment. Future studies should validate these findings and determine whether risk factors might be of influence at an earlier stage (i.e., preclinical) of AD.

Selecting Aβ isoforms for an Alzheimer's disease cerebrospinal fluid biomarker panel

Although the core cerebrospinal fluid Alzheimer's disease (AD) biomarkers amyloid-β (Aβ_1-42) and tau show a high diagnostic accuracy, there are still limitations due to overlap in the biomarker levels with other neurodegenerative and dementia disorders. During Aβ_1-42 production and clearance in the brain, several other Aβ peptides and amyloid precursor protein fragments are formed that could potentially serve as biomarkers for this ongoing disease process. Therefore, this review will present the current status of the findings for amyloid precursor protein and Aβ peptide isoforms in AD and clinically related disorders. In conclusion, adding new Aβ isoforms to the AD biomarker panel may improve early differential diagnostic accuracy and increase the cerebrospinal fluid biomarker concordance with AD neuropathological findings in the brain.

Negative correlation between CSF zinc level and anxiety in male Chinese subjects

Zinc is crucial for brain development and psychiatric regulation. In the present study, we investigated the relationship between cerebrospinal fluid (CSF) zinc level and anxiety in a group of male Chinese subjects. Results demonstrated that zinc levels had no considerable interindividual variations, ranging from 8.37 to 16.83µm. Correlation analyses revealed that CSF Zinc levels were positively correlated with education years (r=0.225, p=0.024) and negatively correlated with SAS scores (r=-0.287, p=0.004), but not associated with age or BMI. In conclusion, this present study suggests that CSF zinc level is associated with anxiety.