Does CSF p-tau181 help to discriminate Alzheimer's disease from other dementias and mild cognitive impairment? A meta-analysis of the literature

The Relationship of Cerebrospinal Fluid Biomarkers and Cognitive Performance in Frontotemporal Dementia

Objective

Currently available literature on the relationships between cerebrospinal fluid (CSF) biomarkers and cognitive performance in frontotemporal dementia (FTD) is very limited and inconclusive. In this study, we investigated the association of cognition, as measured with Montreal Cognitive Assessment (MoCA), with CSF levels of total tau (t-tau), phosphorylated tau at threonine 181 (p-tau181), and amyloid β 1-42 (Aβ1-42) in a group of patients with FTD and Alzheimer's disease (AD).

Methods

We conducted a retrospective cohort study with participants selected from the electronic records of patients seen at Yale New Haven Hospital's Memory Clinic, CT, USA. We included 61 patients, 28 with FTD (mean age=64.1) and 33 with AD (mean age=66.8).

Results

T-tau levels negatively and significantly correlated with total MoCA scores as well as the different MoCA index scores in both the FTD (r=-0.469, p<0.05) and AD (r=-0.545, p<0.01) groups. There were no significant associations with MoCA scores and p-tau181 levels in patients with FTD (r=-0.224, p>0.05), unlike patients with AD, who exhibited significant correlations (r=-0.549, p<0.01). Also, Aβ1-42 levels were not significantly correlated with MoCA scores in either of the FTD and AD groups.

Conclusion

CSF concentrations of t-tau are inversely correlated to cognitive performance in patients with FTD and both t-tau and p-tau181 in AD. These findings provide valuable insights into the relationship between clinical cognitive performance and tau-related pathology in FTD.

The Associations of Phosphorylated Tau 181 and Tau 231 Levels in Plasma and Cerebrospinal Fluid with Cognitive Function in Alzheimer's Disease: A Systematic Review and Meta-Analysis

Background

Cerebrospinal fluid (CSF) or blood biomarkers like phosphorylated tau proteins (p-tau) are used to detect Alzheimer's disease (AD) early. Increasing studies on cognitive function and blood or CSF p-tau levels are controversial.

Objective

Our study examined the potential of p-tau as a biomarker of cognitive status in normal control (NC), mild cognitive impairment (MCI), and AD patients.

Methods

We searched PubMed, Cochrane, Embase, and Web of Science for relevant material through 12 January 2023. 5,017 participants from 20 studies-1,033 AD, 2,077 MCI, and 1,907 NC-were evaluated. Quantitative analysis provided continuous outcomes as SMDs with 95% CIs. Begg tested publication bias.

Results

MCI patients had lower CSF p-tau181 levels than AD patients (SMD =-0.60, 95% CI (-0.85, -0.36)) but higher than healthy controls (SMD = 0.67). AD/MCI patients had greater plasma p-tau181 levels than healthy people (SMD =-0.73, 95% CI (-1.04, -0.43)). MCI patients had significantly lower p-tau231 levels than AD patients in plasma and CSF (SMD =-0.90, 95% CI (-0.82, -0.45)). MCI patients showed greater CSF and plasma p-tau231 than healthy controls (SMD = 1.34, 95% CI (0.89, 1.79) and 0.43, (0.23, 0.64)). Plasma p-tau181/231 levels also distinguished the three categories. MCI patients had higher levels than healthy people, while AD patients had higher levels than MCI patients.

Conclusions

CSF p-tau181 and p-tau231 biomarkers distinguished AD, MCI, and healthy populations. Plasma-based p-tau181 and p-tau231 biomarkers for AD and MCI need further study.

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

IMPORTANCE

Accurately diagnosing neurodegenerative dementia is often challenging due to overlapping clinical features. Disease specific biomarkers could enhance diagnostic accuracy. However, CSF analysis procedures and advanced imaging modalities are either invasive or high-priced, and routinely unavailable. Easily accessible disease biomarkers would be of utmost value for accurate differential diagnosis of dementia subtypes.

OBJECTIVE

To assess the diagnostic accuracy of blood-based biomarkers for the differential diagnosis of AD from Frontotemporal Lobar Degeneration (FTLD), or AD from Dementia with Lewy Bodies (DLB).

METHODS

Systematic review. Three databases (PubMed, Scopus, and Web of Science) were searched. Studies assessing blood-based biomarkers levels in AD versus FTLD, or AD versus DLB, and its diagnostic accuracy, were selected. When the same biomarker was assessed in three or more studies, a meta-analysis was performed. QUADAS-2 criteria were used for quality assessment.

RESULTS

Twenty studies were included in this analysis. Collectively, 905 AD patients were compared to 1262 FTLD patients, and 209 AD patients were compared to 246 DLB patients. Regarding biomarkers for AD versus FTLD, excellent discriminative accuracy (AUC >0.9) was found for p-tau181, p-tau217, synaptophysin, synaptopodin, GAP43 and calmodulin. Other biomarkers also demonstrated good accuracy (AUC = 0.8-0.9). For AD versus DLB distinction, only miR-21-5p and miR-451a achieved excellent accuracy (AUC >0.9).

CONCLUSION

Encouraging results were found for several biomarkers, alone or in combination. Prospective longitudinal designs and consensual protocols, comprising larger cohorts and homogeneous testing modalities across centres, are essential to validate the clinical value of blood biomarkers for the precise etiological diagnosis of dementia.

CSF α-Synuclein and Tau as Biomarkers for Dementia With Lewy Bodies: A Systematic Review and Meta-analysis

OBJECTIVE

This study investigated whether α-synuclein and tau in cerebrospinal fluid (CSF) can be used as biomarkers to diagnose dementia with Lewy bodies (DLB).

MATERIALS AND METHODS

We retrieved 3303 studies with "Dementia with Lewy bodies," "α-synuclein," and "tau" as keywords. We formulated screening criteria, and 2 researchers completed the screening, quality evaluation, and data extraction tasks. Finally, 35 studies related to tau, and 14 studies related to α-synuclein were included. Review Manager 5.4 and Stata16 were used for meta-analysis. Subgroup, sensitivity, and meta-regression analyses were performed to identify sources of heterogeneity and strengthen the results.

RESULTS

Compared with the control group, DLB patients showed significantly higher CSF levels of tau [weighted mean difference=81.36 (59.82, 102.91); Z =7.40; P <0.00001], and lower CSF levels of α-synuclein [weighted mean difference=-95.25 (-162.02, -28.48); Z =2.80; P =0.005]. Mini-Mental State Examination (MMSE) score, male ratio, and disease duration were not sources of heterogeneity on subgroup and meta-regression analyses. Sensitivity analysis revealed no significant differences.

CONCLUSIONS

Higher levels of tau and lower levels of α-synuclein were found in the CSF of patients with DLB compared with the control group. Therefore, CSF tau and α-synuclein levels may be diagnostic biomarkers for DLB.

Cerebrospinal Fluid Biomarkers in Autopsy-Confirmed Alzheimer Disease and Frontotemporal Lobar Degeneration

BACKGROUND AND OBJECTIVES

To determine how fully automated Elecsys CSF immunoassays for β-amyloid (Aβ) and tau biomarkers and an ultrasensitive Simoa assay for neurofilament light chain (NFL) correlate with neuropathologic changes of Alzheimer disease (AD) and frontotemporal lobar degeneration (FTLD).

METHODS

We studied 101 patients with antemortem CSF and neuropathology data. CSF samples were collected a mean of 2.9 years before death (range 0.2-7.5 years). CSF was analyzed for Aβ40, Aβ42, total tau (T-tau), tau phosphorylated at amino acid residue 181 (P-tau), P-tau/Aβ42 and Aβ42/Aβ40 ratios, and NFL. Neuropathology measures included Thal phases, Braak stages, Consortium to Establish a Registry for Alzheimer's Disease (CERAD) scores, AD neuropathologic change (ADNC), and primary and contributory pathologic diagnoses. Associations between CSF biomarkers and neuropathologic features were tested in regression models adjusted for age, sex, and time from sampling to death.

RESULTS

CSF biomarkers were associated with neuropathologic measures of Aβ (Thal, CERAD score), tau (Braak stage), and overall ADNC. The CSF P-tau/Aβ42 and Aβ42/Aβ40 ratios had high sensitivity, specificity, and overall diagnostic performance for intermediate-high ADNC (area under the curve range 0.95-0.96). Distinct biomarker patterns were seen in different FTLD subtypes, with increased NFL and reduced P-tau/T-tau in FTLD-TAR DNA-binding protein 43 and reduced T-tau in progressive supranuclear palsy compared to other FTLD variants.

DISCUSSION

CSF biomarkers, including P-tau, T-tau, Aβ42, Aβ40, and NFL, support in vivo identification of AD neuropathology and correlate with FTLD neuropathology.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that distinct CSF biomarker patterns, including for P-tau, T-tau, Aβ42, Aβ40, and NFL, are associated with AD and FTLD neuropathology.

New insights and therapeutic opportunities for progranulin-deficient frontotemporal dementia

Frontotemporal dementia (FTD) is the second most common form of dementia. It affects the frontal and temporal lobes of the brain and has a highly heterogeneous clinical representation with patients presenting with a wide range of behavioral, language, and executive dysfunctions. Etiology of FTD is complex and consists of both familial and sporadic cases. Heterozygous mutations in the GRN gene, resulting in GRN haploinsufficiency, cause progranulin (PGRN)-deficient FTD characterized with cytoplasmic mislocalization of TAR DNA-binding protein 43 kDa (TDP-43) aggregates. GRN codes for PGRN, a secreted protein that is also localized in the endolysosomes and plays a critical role in regulating lysosomal homeostasis. How PGRN deficiency modulates immunity and causes TDP-43 pathology and FTD-related neurodegeneration remains an active area of intense investigation. In the current review, we discuss some of the significant progress made in the past two years that links PGRN deficiency with microglial-associated neuroinflammation, TDP-43 pathology, and lysosomal dysfunction. We also review the opportunities and challenges toward developing therapies and biomarkers to treat PGRN-deficient FTD.

Neurofilament Proteins as Biomarkers to Monitor Neurological Diseases and the Efficacy of Therapies

Biomarkers of neurodegeneration and neuronal injury have the potential to improve diagnostic accuracy, disease monitoring, prognosis, and measure treatment efficacy. Neurofilament proteins (NfPs) are well suited as biomarkers in these contexts because they are major neuron-specific components that maintain structural integrity and are sensitive to neurodegeneration and neuronal injury across a wide range of neurologic diseases. Low levels of NfPs are constantly released from neurons into the extracellular space and ultimately reach the cerebrospinal fluid (CSF) and blood under physiological conditions throughout normal brain development, maturation, and aging. NfP levels in CSF and blood rise above normal in response to neuronal injury and neurodegeneration independently of cause. NfPs in CSF measured by lumbar puncture are about 40-fold more concentrated than in blood in healthy individuals. New ultra-sensitive methods now allow minimally invasive measurement of these low levels of NfPs in serum or plasma to track disease onset and progression in neurological disorders or nervous system injury and assess responses to therapeutic interventions. Any of the five Nf subunits - neurofilament light chain (NfL), neurofilament medium chain (NfM), neurofilament heavy chain (NfH), alpha-internexin (INA) and peripherin (PRPH) may be altered in a given neuropathological condition. In familial and sporadic Alzheimer's disease (AD), plasma NfL levels may rise as early as 22 years before clinical onset in familial AD and 10 years before sporadic AD. The major determinants of elevated levels of NfPs and degradation fragments in CSF and blood are the magnitude of damaged or degenerating axons of fiber tracks, the affected axon caliber sizes and the rate of release of NfP and fragments at different stages of a given neurological disease or condition directly or indirectly affecting central nervous system (CNS) and/or peripheral nervous system (PNS). NfPs are rapidly emerging as transformative blood biomarkers in neurology providing novel insights into a wide range of neurological diseases and advancing clinical trials. Here we summarize the current understanding of intracellular NfP physiology, pathophysiology and extracellular kinetics of NfPs in biofluids and review the value and limitations of NfPs and degradation fragments as biomarkers of neurodegeneration and neuronal injury.

Biomarkers of vascular cognitive impairment

There is currently no approved list of vascular cognitive impairment biomarkers. The main problem for the practitioner in identifying cognitive impairment in patients is the differential diagnosis of Alzheimer's disease, vascular cognitive impairment, and other diseases, which are much less common. Vascular cognitive impairment includes post-stroke dementia, cognitive dysfunction in cardio-and cerebrovascular diseases. Without etiology identification, it is impossible to prescribe adequate treatment. Another challenge is identifying cognitive impairment before dementia develops. This literature review is devoted to the search and critical analysis of candidates for biomarkers of vascular cognitive impairment and the establishment of markers of moderate cognitive dysfunction. The papers were searched for in the Web of Science and PubMed databases. A list of cerebrospinal fluid, plasma, serum and genetic biomarkers was made, allowing for differential diagnosis between vascular impairment and Alzheimer's disease. The markers of moderate cognitive dysfunction, which make it possible to identify cognitive impairment at the pre-dementia stage, were also identified.

Development of disease-modifying drugs for frontotemporal dementia spectrum disorders

Frontotemporal dementia (FTD) encompasses a spectrum of clinical syndromes characterized by progressive executive, behavioural and language dysfunction. The various FTD spectrum disorders are associated with brain accumulation of different proteins: tau, the transactive response DNA binding protein of 43 kDa (TDP43), or fused in sarcoma (FUS) protein, Ewing sarcoma protein and TATA-binding protein-associated factor 15 (TAF15) (collectively known as FET proteins). Approximately 60% of patients with FTD have autosomal dominant mutations in C9orf72, GRN or MAPT genes. Currently available treatments are symptomatic and provide limited benefit. However, the increased understanding of FTD pathogenesis is driving the development of potential disease-modifying therapies. Most of these drugs target pathological tau - this category includes tau phosphorylation inhibitors, tau aggregation inhibitors, active and passive anti-tau immunotherapies, and MAPT-targeted antisense oligonucleotides. Some of these therapeutic approaches are being tested in phase II clinical trials. Pharmacological approaches that target the effects of GRN and C9orf72 mutations are also in development. Key results of large clinical trials will be available in a few years. However, clinical trials in FTD pose several challenges, and the development of specific brain imaging and molecular biomarkers could facilitate the recruitment of clinically homogenous groups to improve the chances of positive clinical trial results.

Cerebrospinal fluid α-synuclein contributes to the differential diagnosis of Alzheimer's disease

INTRODUCTION

The ability of Alzheimer's disease (AD) cerebrospinal fluid (CSF) biomarkers (amyloid β peptide 1-42, total tau, and phosphorylated tau) to discriminate AD from related disorders is limited. Biomarkers for other concomitant pathologies (e.g., CSF α-synuclein [α-syn] for Lewy body pathology) may be needed to further improve the differential diagnosis.

METHODS

CSF total α-syn, phosphorylated α-syn at Ser129, and AD CSF biomarkers were evaluated with Luminex immunoassays in 367 participants, followed by validation in 74 different neuropathologically confirmed cases.

RESULTS

CSF total α-syn, when combined with amyloid β peptide 1-42 and either total tau or phosphorylated tau, improved the differential diagnosis of AD versus frontotemporal dementia, Lewy body disorders, or other neurological disorders. The diagnostic accuracy of the combined models attained clinical relevance (area under curve ∼0.9) and was largely validated in neuropathologically confirmed cases.

DISCUSSION

Combining CSF biomarkers representing AD and Lewy body pathologies may have clinical value in the differential diagnosis of AD.

Cerebrospinal Fluid Biomarkers for the Differential Diagnosis between Alzheimer's Disease and Frontotemporal Lobar Degeneration: Systematic Review, HSROC Analysis, and Confounding Factors

BACKGROUND

Differential diagnosis in dementia is at present one of the main challenges both in clinical practice and research. Cerebrospinal fluid (CSF) biomarkers are included in the current diagnostic criteria of Alzheimer's disease (AD) but their clinical utility is still unclear.

OBJECTIVE

We performed a systematic review of studies analyzing the diagnostic performance of CSF Aβ42, total tau (t-tau), and phosphorylated tau (p-tau) in the discrimination between AD and frontotemporal lobar degeneration (FTLD) dementias.

METHODS

The following electronic databases were consulted until May 2016: Medline and PreMedline, EMBASE, PsycInfo, CINAHL, Cochrane Library, and CRD. For the first-time in the field, a Hierarchical Summary Receiver Operating Characteristic (HRSOC) model was applied, which avoids methodological problems of meta-analyses based on summary points of sensitivity and specificity values. We also investigated relevant confounders of CSF biomarkers' diagnostic performance such as age, disease duration, and global cognitive impairment.

RESULTS

The p-tau/Aβ42 ratio showed the best diagnostic performance. No statistically significant effects of the confounders were observed. Nonetheless, the p-tau/Aβ42 ratio may be especially indicated for younger patients. P-tau may be preferable for less cognitively impaired patients (high MMSE scores) and the t-tau/Aβ42 ratio for more cognitively impaired patients (low MMSE scores).

CONCLUSION

The p-tau/Aβ42 ratio has potential for being implemented in the clinical routine for the differential diagnosis between AD and FTLD. It is of utmost importance that future studies report information on confounders such as age, disease duration, and cognitive impairment, which should also stimulate understanding of the role of these factors in disease mechanisms and pathophysiology.

Fluid and imaging biomarkers for Alzheimer's disease: Where we stand and where to head to

There is increasing evidence that a number of potentially informative biomarkers for Alzheimer disease (AD) can improve the accuracy of diagnosing this form of dementia, especially when used as a panel of diagnostic assays and interpreted in the context of neuroimaging and clinical data. Moreover, by combining the power of CSF biomarkers with neuroimaging techniques to visualize Aβ deposits (or neurodegenerative lesions), it might be possible to better identify individuals at greatest risk for developing MCI and converting to AD. The objective of this article was to review recent progress in selected imaging and chemical biomarkers for prediction, early diagnosis and progression of AD. We present our view point of a scenario that places CSF and imaging markers on the verge of general utility based on accuracy levels that already match (or even surpass) current clinical precision.

Associations between [18F]AV1451 tau PET and CSF measures of tau pathology in a clinical sample

OBJECTIVE

To assess the relationships between fluid and imaging biomarkers of tau pathology and compare their diagnostic utility in a clinically heterogeneous sample.

METHODS

Fifty-three patients (28 with clinical Alzheimer disease [AD] and 25 with non-AD clinical neurodegenerative diagnoses) underwent β-amyloid (Aβ) and tau ([¹⁸F]AV1451) PET and lumbar puncture. CSF biomarkers (Aβ₄₂, total tau [t-tau], and phosphorylated tau [p-tau]) were measured by multianalyte immunoassay (AlzBio3). Receiver operator characteristic analyses were performed to compare discrimination of Aβ-positive AD from non-AD conditions across biomarkers. Correlations between CSF biomarkers and PET standardized uptake value ratios (SUVR) were assessed using skipped Pearson correlation coefficients. Voxelwise analyses were run to assess regional CSF-PET associations.

RESULTS

[¹⁸F]AV1451-PET cortical SUVR and p-tau showed excellent discrimination between Aβ-positive AD and non-AD conditions (area under the curve 0.92-0.94; ≤0.83 for other CSF measures), and reached 83% classification agreement. In the full sample, cortical [¹⁸F]AV1451 was associated with all CSF biomarkers, most strongly with p-tau (r = 0.75 vs 0.57 for t-tau and -0.49 for Aβ₄₂). When restricted to Aβ-positive patients with AD, [¹⁸F]AV1451 SUVR correlated modestly with p-tau and t-tau (both r = 0.46) but not Aβ₄₂ (r = 0.02). On voxelwise analysis, [¹⁸F]AV1451 correlated with CSF p-tau in temporoparietal cortices and with t-tau in medial prefrontal regions. Within AD, Mini-Mental State Examination scores were associated with [¹⁸F]AV1451-PET, but not CSF biomarkers.

CONCLUSION

[¹⁸F]AV1451-PET and CSF p-tau had comparable value for differential diagnosis. Correlations were robust in a heterogeneous clinical group but attenuated (although significant) in AD, suggesting that fluid and imaging biomarkers capture different aspects of tau pathology.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that, in a clinical sample of patients with a variety of suspected neurodegenerative diseases, both CSF p-tau and [¹⁸F]AV1451 distinguish AD from non-AD conditions.

Differential role of CSF fatty acid binding protein 3, α-synuclein, and Alzheimer's disease core biomarkers in Lewy body disorders and Alzheimer's dementia

Background

Neurodegenerative disorders such as Alzheimer’s disease (AD), Parkinson’s disease with dementia (PDD), and dementia with Lewy bodies (DLB) share clinical and molecular features. Cerebrospinal fluid (CSF) biomarkers may help the characterization of these diseases, improving the differential diagnosis. We evaluated the diagnostic performance of five CSF biomarkers across a well-characterized cohort of patients diagnosed with AD, DLB, PDD, and Parkinson’s disease (PD).

Methods

A total of 208 patients were enrolled in 3 European centers. The diagnostic groups (AD, n = 48; DLB, n = 40; PDD, n = 20; PD, n = 54) were compared with cognitively healthy neurological control subjects (patients with other neurological diseases [OND], n = 46). CSF levels of fatty acid binding protein 3, heart type (FABP3), α-synuclein (α-syn), amyloid-β peptide 1–42, total tau (t-tau), and phosphorylated tau 181 (p-tau) were assessed with immunoassays. Univariate and multivariate statistical analyses were applied to calculate the diagnostic value of the biomarkers as well as their association with clinical scores.

Results

FABP3 levels were significantly increased in patients with AD and DLB compared with those with PD and OND (p < 0.001). CSF t-tau, p-tau, and α-syn were significantly higher in patients with AD than in patients with PDD, DLB, PD, and OND. Combination of FABP3 with p-tau showed high accuracy for the differential diagnosis between AD and DLB (AUC 0.92), whereas patients with AD were separated from those with PDD using a combination of p-tau, FABP3, and α-syn (AUC 0.96). CSF FABP3 was inversely associated with Mini Mental State Examination score in the whole cohort (r = −0.42, p < 0.001).

Conclusions

The combination of CSF biomarkers linked to different aspects of neurodegeneration, such as FABP3, α-syn, and AD biomarkers, improves the biochemical characterization of AD and Lewy body disorders.

Electronic supplementary material

The online version of this article (doi:10.1186/s13195-017-0276-4) contains supplementary material, which is available to authorized users.

Phenotype of postural instability/gait difficulty in Parkinson disease: relevance to cognitive impairment and mechanism relating pathological proteins and neurotransmitters

Parkinson disease (PD) is identified as tremor-dominant (TD) and postural instability and gait difficulty (PIGD) phenotypes. The relationships between motor phenotypes and cognitive impairment and the underlying mechanisms relating pathological proteins and neurotransmitters in cerebrospinal fluid (CSF) are unknown. We evaluated the motor symptoms and cognitive function by scales, and detected the levels of pathological proteins and neurotransmitters in CSF. TD group and PIGD group had significantly higher levels of total tau, tau phosphorylated at the position of threonine 181(P-tau181t), threonine 231, serine 396, serine 199 and lower β amyloid (Aβ)_1–42 level in CSF than those in control group; PIGD group had significantly higher P-tau181t level and lower Aβ_1–42 level than those in TD group. In PD group, PIGD severity was negatively correlated with MoCA score and Aβ_1–42 level in CSF, and positively correlated with Hoehn-Yahr stage and P-tau181t level in CSF. In PIGD group, PIGD severity was negatively correlated with homovanillic acid (HVA) level in CSF, and HVA level was positively correlated with Aβ_1–42 level in CSF. PIGD was significantly correlated with cognitive impairment, which underlying mechanism might be involved in Aβ_1–42 aggregation in brain and relevant neurochemical disturbance featured by the depletion of HVA in CSF.

Diagnostic Value of Cerebrospinal Fluid Biomarkers (Phospho-Tau181, total-Tau, Aβ42, and Aβ40) in Prodromal Stage of Alzheimer's Disease and Dementia with Lewy Bodies

BACKGROUND

Dementia with Lewy bodies (DLB) symptoms are close to those of Alzheimer's disease (AD), and the differential diagnosis is difficult especially early in the disease. Unfortunately, AD biomarkers in cerebrospinal fluid (CSF), and more particularly Aβ1 - 42, appear to be altered in dementia with Lewy bodies (DLB). However, the level of these biomarkers has never been studied in the prodromal stage of the disease.

OBJECTIVE

To compare these biomarkers between DLB and AD, with a particular focus on the prodromal stage.

METHODS

A total of 166 CSF samples were collected at the memory clinic of Strasbourg. They were obtained from prodromal DLB (pro-DLB), DLB dementia, prodromal AD (pro-AD), and AD dementia patients, and elderly controls. Phospho-Tau181, total-Tau, Aβ42, and Aβ40 were measured in the CSF.

RESULTS

At the prodromal stage, contrary to AD patients, DLB patients' biomarker levels in the CSF were not altered. At the demented stage of DLB, Aβ42 levels were reduced as well as Aβ40 levels. Thus, the Aβ42/Aβ40 ratio remained unchanged between the prodromal and demented stages, contrary to what was observed in AD. Tau and Phospho-Tau181 levels were unaltered in DLB patients.

CONCLUSIONS

We have shown that at the prodromal stage the DLB patients had no pathological profile. Consequently, CSF AD biomarkers are extremely useful for differentiating AD from DLB patients particularly at this stage when the clinical diagnosis is difficult. Thus, these results open up new perspectives on the interpretation of AD biomarkers in DLB.

Use of CSF α-synuclein in the differential diagnosis between Alzheimer's disease and other neurodegenerative disorders

BACKGROUND

The etiology and pathogenesis of neurodegenerative disorders has yet to be elucidated, so their differential diagnosis is a challenge. This is especially true in differentiating Alzheimer's disease (AD), dementia with Lewy bodies (DLB), Parkinson disease (PD), and multiple system atrophy (MSA).

METHODS

A total of 11 eligible articles were identified by search of electronic databases including PubMed, Springer Link, Elsevier, and the Cochrane Library, up to June 2014. In meta-analyses, standardized mean differences (SMD), with 95% confidence intervals (CI), comparing cerebrospinal fluid (CSF) measures of α-synuclein between the above conditions were calculated using random-effects models.

RESULTS

CSF α-synuclein concentrations were significantly higher in AD compared to DLB [SMD: 0.32, 95% CI: (0.02, 0.62), z = 2.07, P = 0.038]; PD [SMD: 0.87, 95% CI: (0.15, 1.58), z = 2.38, P = 0.017]; or MSA [SMD: 1.14, 95% CI: (0.15, 2.14), z = 2.25, P = 0.025]. However, no significant difference was found between patients with AD and neurological cognitively normal controls [SMD: 0.02, 95% CI: (-0.21, 0.24), z = 0.13, P = 0.894].

CONCLUSIONS

Results of these meta-analysis suggest that quantification of CSF α-synuclein could help distinguish AD from other neurodegenerative disorders such as DLB, PD, or MSA.

Alzheimer's disease--Recent biomarker developments in relation to updated diagnostic criteria

Alzheimer's disease (AD) is the most common cause of dementia and is characterized by neuroaxonal and synaptic degeneration accompanied by intraneuronal neurofibrillary tangles and accumulation of extracellular plaques in specific brain regions. These features are reflected in the AD cerebrospinal fluid (CSF) by increased concentrations of total tau (t-tau) and phosphorylated tau (p-tau), together with decreased concentrations of β-amyloid (Aβ42), respectively. In combination, Aβ42, p-tau and t-tau are 85-95% sensitive and specific for AD in both prodromal and dementia stages of the disease and they are now included in the diagnostic research criteria for AD. However, to fully implement these biomarkers into clinical practice, harmonization of data is needed. This work is ongoing through the standardization of analytical procedures between clinical laboratories and the production of reference materials for CSF Aβ42, p-tau and t-tau. To monitor other aspects of AD neuropathology, e.g., synaptic dysfunction and/or to develop markers of progression, identifying novel candidate biomarkers is of great importance. Based on knowledge from the established biomarkers, exemplified by Aβ and its many variants, and emerging data on neurogranin fragments as biomarker candidate(s), a thorough protein characterization in order to fully understand the diagnostic value of a protein is a suggested approach for successful biomarker discovery.

Genetics and underlying pathology of dementia

As the population steadily ages, dementia, in all its forms, remains a great societal challenge. Yet, our knowledge of their etiology remains rather limited. To this end, genetic studies can give us insight into the underlying mechanisms that lead to the development of dementia, potentially facilitating treatments in the future. In this review we cover the most recent genetic risk factors associated with the onset of the four most common dementia types today, including Alzheimer's disease (AD), Vascular Dementia (VaD), Frontotemporal Lobar Degeneration (FTLD) and Lewy Body Dementia (LBD). Moreover, we discuss the overlap in major underlying pathologies of dementia derived from their genetic associations. While all four dementia types appear to involve genes associated with tau-pathology and neuroinflammation only LBD, AD and VaD appear to involve amyloid genes while LBD and FTLD share alpha synuclein genes. Together these findings suggest that some of the dementias may exist along a spectrum and demonstrates the necessity to conduct large-scale studies pinpointing the etiology of the dementias and potential gene and environment interactions that may influence their development.