Exploring the potential of fully automated LUMIPULSE G plasma assays for detecting Alzheimer's disease pathology.

BACKGROUND: LUMIPULSE G-automated immunoassays represent a widely used method for the quantification of Alzheimer's disease (AD) biomarkers in the cerebrospinal fluid (CSF). Less invasive blood-based markers confer a promising tool for AD diagnosis at prodromal stages (mild cognitive impairment (MCI)). Highly sensitive assays for the quantification of amyloid-beta (Aß) and phosphorylated Tau-181 (p-Tau181) in the blood are showing promising results. In this study, we evaluated the clinical performance of the recently available fully automated LUMIPULSE plasma marker assays for detecting brain AD pathology and for predicting progression from MCI to AD dementia stage. METHODS: A retrospective exploratory cohort of 138 individuals (22 neurological controls [NC], 72 MCI, and 44 AD dementia patients) was included. Data regarding baseline CSF concentrations of Aß42, Aß40, t-Tau, and p-Tau181 was available and used to establish the presence of AD brain pathology. Baseline Aß42, Aß40, and p-Tau181 concentrations were determined in stored plasma samples using high-throughput fully automated LUMIPULSE assays. Progression from MCI to AD dementia was evaluated during follow-up (mean 6.4 ± 2.5 years). Moreover, a prospective validation cohort of 72 individuals with memory complaints underwent AD biomarker quantification, closely mirroring typical clinical practice. This cohort aimed to confirm the study's main findings. RESULTS: In the exploratory cohort, correlations between CSF and plasma were moderate for p-Tau181 (ρ = 0.61, p < 0.001) and weak for Aß42/Aß40 ratio (ρ = 0.39, p < 0.001). Plasma p-Tau181 and p-Tau181/Aß42 concentrations were significantly increased while Aß42/Aß40 was significantly decreased (p < 0.001) in patients with AD dementia and prodromal AD, as well as in individuals with CSF abnormal amyloid concentrations (A +). Plasma p-Tau181 showed a robust performance in differentiating patients clinically diagnosed as AD (AUC = 0.89; 95% CI 0.83-0.94); A + vs. A - (AUC = 0.84, 95% CI 0.77-0.91) and also in predicting conversion to AD dementia in MCI patients (AUC = 0.89, 95% CI 0.81-0.96). When tested in the validation cohort, plasma p-Tau181 displayed 83.3% of the overall percentage of agreement according to amyloid status. CONCLUSIONS: Our results show that the measurement of p-Tau181 in plasma has great potential as a non-invasive prognostic screening tool for implementation in a clinical setting.

Association of Structural Forms of 17q21.31 with the Risk of Progressive Supranuclear Palsy and MAPT Sub-haplotypes.

Importance: The chromosome 17q21.31 region, containing a 900 Kb inversion that defines H1 and H2 haplotypes, represents the strongest genetic risk locus in progressive supranuclear palsy (PSP). In addition to H1 and H2, various structural forms of 17q21.31, characterized by the copy number of α, ß, and γ duplications, have been identified. However, the specific effect of each structural form on the risk of PSP has never been evaluated in a large cohort study. Objective: To assess the association of different structural forms of 17q.21.31, defined by the copy numbers of α, ß, and γ duplications, with the risk of PSP and MAPT sub-haplotypes. Design setting and participants: Utilizing whole genome sequencing data of 1,684 (1,386 autopsy confirmed) individuals with PSP and 2,392 control subjects, a case-control study was conducted to investigate the association of copy numbers of α, ß, and γ duplications and structural forms of 17q21.31 with the risk of PSP. All study subjects were selected from the Alzheimer's Disease Sequencing Project (ADSP) Umbrella NG00067.v7. Data were analyzed between March 2022 and November 2023. Main outcomes and measures: The main outcomes were the risk (odds ratios [ORs]) for PSP with 95% CIs. Risks for PSP were evaluated by logistic regression models. Results: The copy numbers of α and ß were associated with the risk of PSP only due to their correlation with H1 and H2, while the copy number of γ was independently associated with the increased risk of PSP. Each additional duplication of γ was associated with 1.10 (95% CI, 1.04-1.17; P = 0.0018) fold of increased risk of PSP when conditioning H1 and H2. For the H1 haplotype, addition γ duplications displayed a higher odds ratio for PSP: the odds ratio increases from 1.21 (95%CI 1.10-1.33, P = 5.47 × 10-5) for H1ß1γ1 to 1.29 (95%CI 1.16-1.43, P = 1.35 × 10-6) for H1ß1γ2, 1.45 (95%CI 1.27-1.65, P = 3.94 × 10-8) for H1ß1γ3, and 1.57 (95%CI 1.10-2.26, P = 1.35 × 10-2) for H1ß1γ4. Moreover, H1ß1γ3 is in linkage disequilibrium with H1c (R2 = 0.31), a widely recognized MAPT sub-haplotype associated with increased risk of PSP. The proportion of MAPT sub-haplotypes associated with increased risk of PSP (i.e., H1c, H1d, H1g, H1o, and H1h) increased from 34% in H1ß1γ1 to 77% in H1ß1γ4. Conclusions and relevance: This study revealed that the copy number of γ was associated with the risk of PSP independently from H1 and H2. The H1 haplotype with more γ duplications showed a higher odds ratio for PSP and were associated with MAPT sub-haplotypes with increased risk of PSP. These findings expand our understanding of how the complex structure at 17q21.31 affect the risk of PSP.

Performance of a fully-automated Lumipulse plasma phospho-tau181 assay for Alzheimer's disease.

BACKGROUND: The recent promise of disease-modifying therapies for Alzheimer's disease (AD) has reinforced the need for accurate biomarkers for early disease detection, diagnosis and treatment monitoring. Advances in the development of novel blood-based biomarkers for AD have revealed that plasma levels of tau phosphorylated at various residues are specific and sensitive to AD dementia. However, the currently available tests have shortcomings in access, throughput, and scalability that limit widespread implementation. METHODS: We evaluated the diagnostic and prognostic performance of a high-throughput and fully-automated Lumipulse plasma p-tau181 assay for the detection of AD. Plasma from older clinically unimpaired individuals (CU, n = 463) and patients with mild cognitive impairment (MCI, n = 107) or AD dementia (n = 78) were obtained from the longitudinal Stanford University Alzheimer's Disease Research Center (ADRC) and the Stanford Aging and Memory Study (SAMS) cohorts. We evaluated the discriminative accuracy of plasma p-tau181 for clinical AD diagnosis, association with amyloid ß peptides and p-tau181 concentrations in CSF, association with amyloid positron emission tomography (PET), and ability to predict longitudinal cognitive and functional change. RESULTS: The assay showed robust performance in differentiating AD from control participants (AUC 0.959, CI: 0.912 to 0.990), and was strongly associated with CSF p-tau181, CSF Aß42/Aß40 ratio, and amyloid-PET global SUVRs. Associations between plasma p-tau181 with CSF biomarkers were significant when examined separately in Aß+ and Aß- groups. Plasma p-tau181 significantly increased over time in CU and AD diagnostic groups. After controlling for clinical diagnosis, age, sex, and education, baseline plasma p-tau181 predicted change in MoCA overall and change in CDR Sum of Boxes in the AD group over follow-up of up to 5 years. CONCLUSIONS: This fully-automated and available blood-based biomarker assay therefore may be useful for early detection, diagnosis, prognosis, and treatment monitoring of AD.

Validation of the LUMIPULSE automated immunoassay for the measurement of core AD biomarkers in cerebrospinal fluid.

OBJECTIVES: The core cerebrospinal fluid (CSF) biomarkers; total tau (tTau), phospho-tau (pTau), amyloid ß 1-42 (Aß 1-42), and the Aß 1-42/Aß 1-40 ratio have transformed Alzheimer's disease (AD) research and are today increasingly used in clinical routine laboratories as diagnostic tools. Fully automated immunoassay instruments with ready-to-use assay kits and calibrators has simplified their analysis and improved reproducibility of measurements. We evaluated the analytical performance of the fully automated immunoassay instrument LUMIPULSE G (Fujirebio) for measurement of the four core AD CSF biomarkers and determined cutpoints for AD diagnosis. METHODS: Comparison of the LUMIPULSE G assays was performed with the established INNOTEST ELISAs (Fujirebio) for hTau Ag, pTau 181, ß-amyloid 1-42, and with V-PLEX Plus Aß Peptide Panel 1 (6E10) (Meso Scale Discovery) for Aß 1-42/Aß 1-40, as well as with a LC-MS reference method for Aß 1-42. Intra- and inter-laboratory reproducibility was evaluated for all assays. Clinical cutpoints for Aß 1-42, tTau, and pTau was determined by analysis of three cohorts of clinically diagnosed patients, comprising 651 CSF samples. For the Aß 1-42/Aß 1-40 ratio, the cutpoint was determined by mixture model analysis of 2,782 CSF samples. RESULTS: The LUMIPULSE G assays showed strong correlation to all other immunoassays (r>0.93 for all assays). The repeatability (intra-laboratory) CVs ranged between 2.0 and 5.6%, with the highest variation observed for ß-amyloid 1-40. The reproducibility (inter-laboratory) CVs ranged between 2.1 and 6.5%, with the highest variation observed for ß-amyloid 1-42. The clinical cutpoints for AD were determined to be 409 ng/L for total tau, 50.2 ng/L for pTau 181, 526 ng/L for ß-amyloid 1-42, and 0.072 for the Aß 1-42/Aß 1-40 ratio. CONCLUSIONS: Our results suggest that the LUMIPULSE G assays for the CSF AD biomarkers are fit for purpose in clinical laboratory practice. Further, they corroborate earlier presented reference limits for the biomarkers.

Comparing CSF amyloid-beta biomarker ratios for two automated immunoassays, Elecsys and Lumipulse, with amyloid PET status.

INTRODUCTION: We evaluated for two novel automated biomarker assays how cerebrospinal fluid (CSF) amyloid beta (Aß)1- 42-ratios improved the concordance with amyloid positron emission tomography (PET) positivity compared to Aß1- 42 alone. METHODS: We selected 288 individuals from the Amsterdam Dementia Cohort across the Alzheimer's disease clinical spectrum when they had both CSF and amyloid PET visual read available, regardless of diagnosis. CSF Aß1- 42, phosphorylated tau (p-tau), and total tau (t-tau) were measured with Elecsys and Lumipulse assays, and Aß1-40 with Lumipulse. CSF cut-points were defined using receiver operating characteristic (ROC) for amyloid PET positivity. RESULTS: For both Elecsys and Lumipulse the p-tau/Aß1- 42, Aß1- 42/Aß1- 40, and t-tau/Aß1- 42 ratios showed similarly good concordance with amyloid PET (Elecsys: 93,90,90%; Lumipulse: 94,92,90%) and were higher than Aß1- 42 alone (Elecsys 85%; Lumipulse 84%). DISCUSSION: Biomarker ratios p-tau/Aß1- 42, Aß1- 42/Aß1- 40, t-tau/Aß1- 42 on two automated platforms show similar optimal concordance with amyloid PET in a memory clinic cohort.

Clinical validation of the Lumipulse G cerebrospinal fluid assays for routine diagnosis of Alzheimer's disease.

BACKGROUND: Ongoing efforts within the Alzheimer's disease (AD) field have focused on improving the intra- and inter-laboratory variability for cerebrospinal fluid (CSF) biomarkers. Fully automated assays offer the possibility to eliminate sample manipulation steps and are expected to contribute to this improvement. Recently, fully automated chemiluminescence enzyme immunoassays for the quantification of all four AD biomarkers in CSF became available. The aims of this study were to (i) evaluate the analytical performance of the Lumipulse G ß-Amyloid 1-42 (restandardized to Certified Reference Materials), ß-Amyloid 1-40, total Tau, and pTau 181 assays on the fully automated LUMIPULSE G600II; (ii) compare CSF biomarker results of the Lumipulse G assays with the established manual ELISA assays (INNOTEST®) from the same company (Fujirebio); and (iii) establish cut-off values and the clinical performance of the Lumipulse G assays for AD diagnosis. METHODS: Intra- and inter-assay variation was assessed in CSF samples with low, medium, and high concentrations of each parameter. Method comparison and clinical evaluation were performed on 40 neurological controls (NC) and 80 patients with a diagnosis of probable AD supported by a follow-up ≥ 3 years and/or positive amyloid PET imaging. A small validation cohort of 10 NC and 20 AD patients was also included to validate the cut-off values obtained on the training cohort. RESULTS: The maximal observed intra-assay and inter-assay coefficients of variation (CVs) were 3.25% and 5.50%, respectively. Method comparisons revealed correlation coefficients ranging from 0.89 (for Aß40) to 0.98 (for t-Tau), with those for Aß42 (0.93) and p-Tau (0.94) in-between. ROC curve analysis showed area under the curve values consistently above 0.85 for individual biomarkers other than Aß40, and with the Aß42/40, Aß42/t-Tau, and Aß42/p-Tau ratios outperforming Aß42. Validation of the cut-off values in the independent cohort showed a sensitivity ranging from 75 to 95% and a specificity of 100%. The overall percentage of agreement between Lumipulse and INNOTEST was very high (> 87.5%). CONCLUSIONS: The Lumipulse G assays show a very good analytical performance that makes them well-suited for CSF clinical routine measurements. The good clinical concordance between the Lumipulse G and INNOTEST assays facilitates the implementation of the new method in routine practice.

Agreement of amyloid PET and CSF biomarkers for Alzheimer's disease on Lumipulse.

OBJECTIVE: To determine the cutoffs that optimized the agreement between 18 F-Florbetapir positron emission tomography (PET) and Aß1-42, Aß1-40, tTau, pTau and their ratios measured in cerebrospinal fluid (CSF) on the LUMIPULSE G600II instrument, we quantified the levels of these four biomarkers in 94 CSF samples from participants of the Sant Pau Initiative on Neurodegeneration (SPIN cohort) using the Lumipulse G System with available 18 F-Florbetapir imaging. METHODS: Participants had mild cognitive impairment (n = 35), AD dementia (n = 12), other dementias or neurodegenerative diseases (n = 41), or were cognitively normal controls (n = 6). Levels of Aß1-42 were standardized to certified reference material. Amyloid scans were assessed visually and through automated quantification. We determined the cutoffs of CSF biomarkers that optimized their agreement with 18 F-Florbetapir PET and evaluated concordance between markers of the amyloid category. RESULTS: Aß1-42, tTau and pTau (but not Aß1-40) and the ratios with Aß1-42 had good diagnostic agreement with 18 F-Florbetapir PET. As a marker of amyloid pathology, the Aß1-42/Aß1-40 ratio had higher agreement and better correlation with amyloid PET than Aß1-42 alone. INTERPRETATION: CSF biomarkers measured with the Lumipulse G System show good agreement with amyloid imaging in a clinical setting with heterogeneous presentations of neurological disorders. Combination of Aß1-42 with Aß1-40 increases the agreement between markers of amyloid pathology.

Impact of CSF storage volume on the analysis of Alzheimer's disease biomarkers on an automated platform.

OBJECTIVES: To assess the potential influence of the ratio between the storage tube surface area and the volume of cerebrospinal fluid (CSF) (surface/volume) on the quantifications of four Alzheimer's disease (AD) biomarkers on the Lumipulse G600II automated platform. METHODS: CSF samples of 10 consecutive patients were stored in 2 ml polypropylene tubes containing four different CSF volumes: 1.5 ml, 1 ml, 0.5 ml and 0.25 ml. Concentration of CSF Aß1-42, Aß1-40, t-Tau and p-Tau were measured in all aliquots using the LUMIPULSE G600II automated platform from Fujirebio. RESULTS: Levels of CSF Aß1-42 and Aß1-40 were lower in samples stored with lower volumes (higher surface/volume ratios). This decrease was partly compensated by using the ratio Aß1-42/Aß1-40. Quantification of t-Tau and p-Tau were not influenced by this pre-analytical condition. CONCLUSION: The surface/volume ratio can potentially influence the results of amyloid AD biomarkers. It appears essential to take into account the surface/volume ratio of the storage tubes when quantifying CSF biomarkers in clinical routine.

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 Aß1 - 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.

Importance and impact of preanalytical variables on Alzheimer disease biomarker concentrations in cerebrospinal fluid.

BACKGROUND: Analyses of cerebrospinal fluid (CSF) biomarkers (ß-amyloid protein, total tau protein, and hyperphosphorylated tau protein) are part of the diagnostic criteria of Alzheimer disease. Different preanalytical sample procedures contribute to variability of CSF biomarker concentrations, hampering between-laboratory comparisons. The aim of this study was to explore the influence of fractionated sampling, centrifugation, freezing temperature, freezing delay, and freeze-thaw cycles on CSF biomarker analyses. METHODS: We studied fractionated sampling in sequential aliquots of lumbar CSF. Centrifuged and noncentrifuged samples from the same fraction were compared. CSF samples were subjected to different protocols (liquid nitrogen, -80 °C, and -20 °C; 24 h at 2-8 °C; and 24 and 48 h at room temperature). To study the influence of freeze-thaw cycles, samples were thawed up to 4 times and refrozen at -80 °C. CSF was collected in polypropylene tubes. We measured CSF biomarker concentrations with commercially available single-analyte Innotest assays. RESULTS: CSF biomarker concentrations from non-blood-contaminated samples are not influenced by centrifugation or fractionated sampling. Freezing temperature and delayed storage can affect biomarker concentrations; freezing of CSF samples at -80 °C as soon as possible after collection is recommended. Consecutive freezing and thawing of CSF samples up to 3 times had little effect. CONCLUSIONS: Temperature of freezing, delay until freezing, and freeze-thaw cycles significantly influence CSF biomarker concentrations, stressing the need for standard operating procedures for preanalytical sample handling. The differences observed in this study are, however, relatively small, and the impact on the clinical value of these CSF biomarkers needs to be determined.

Overdiagnosing Vascular Dementia using Structural Brain Imaging for Dementia Work-Up.

Hypothesizing that non-significant cerebrovascular lesions on structural brain imaging lead to overdiagnosis of a vascular etiology of dementia as compared to autopsy-confirmed diagnosis, we set up a study including 71 patients with autopsy-confirmed diagnoses. Forty-two patients in the population (59%) appeared to have definite Alzheimer's disease (AD), whereas 29 (41%) had a non-AD dementia form. The panel clinically diagnosed possible or probable vascular dementia (VaD) in 27 (38%) patients, whereas only five (19%) patients (p = 0.017) had an autopsy-confirmed diagnosis of VaD. Patients with vascular lesions on structural brain imaging were often misdiagnosed as possible or probable VaD as compared to autopsy-confirmed diagnosis.

Agitation-associated behavioral symptoms in mild cognitive impairment and Alzheimer's dementia.

OBJECTIVES: The aim of this study is to determine the prevalence of agitation in mild cognitive impairment (MCI, Petersen's criteria) and patients with Alzheimer's dementia (AD), and to characterize the associated behavioral symptoms. METHOD: A cross-sectional analysis of baseline data from a prospective, longitudinal study on behavioral symptoms was performed, including 268 MCI and 393 AD patients. Behavioral assessment was performed through Middelheim Frontality Score (MFS), Behavioral Pathology in Alzheimer's Disease Rating Scale (Behave-AD) and Cornell Scale for Depression in Dementia (CSDD). Agitated behavior was considered to be clinically relevant when one or more items of the Cohen-Mansfield Agitation Inventory (CMAI) occurred at least once a week. RESULTS: The prevalence of agitation in AD (76%) was higher than in MCI (60%; p < 0.001). Patients with agitation showed more severe frontal lobe, behavioral and depressive symptoms (MFS, Behave-AD and CSDD total scores). In agitated AD patients, all behavioral symptoms and types of agitation were more severe compared to non-agitated AD patients, but in agitated MCI patients only for diurnal rhythm disturbances. This resulted in more severe Behave-AD global scores in patients with agitation as compared to patients without agitation. Comparing MCI and AD patients, MCI patients with agitation showed more severe behavioral and depressive symptoms than AD patients without agitation. The structure of agitation in AD consisted of more aggressive and physically non-aggressive behavior than in MCI. CONCLUSION: Frontal lobe, behavioral and depressive symptoms are more severe in MCI and AD patients with clinically relevant agitation as compared to patients without agitation. However, this association is less pronounced in MCI.

Increased CSF α-synuclein levels in Alzheimer's disease: correlation with tau levels.

BACKGROUND: Given the difficult clinical differential diagnosis between Alzheimer's disease (AD) and dementia with Lewy bodies (DLB), growing interest resulted in research on α-synuclein as a potential cerebrospinal fluid biomarker (CSF) for synucleinopathies. METHODS: CSF α-synuclein-140 concentrations were determined by a prototype xMAP™ bead-based assay (Innogenetics NV, Belgium). In addition, CSF amyloid ß1-42 (Aß1-42), total tau (T-tau), and phosphorylated tau (P-tau181P) levels were determined. RESULTS: CSF α-synuclein levels were higher in AD patients as compared with cognitively healthy controls (P=.019) and patients with synucleinopathies (P<.001). CSF α-synuclein levels were correlated with T-tau (P<.001) and P-tau181P (P<.001) levels in autopsy-confirmed AD patients. A diagnostic algorithm using α-synuclein and P-tau181P discriminated neuropathologically confirmed AD from DLB patients, resulting in sensitivity and specificity values of 85% and 81%, respectively. CONCLUSION: Because CSF α-synuclein levels were significantly higher in AD as compared with synucleinopathies, α-synuclein might have a value as a biomarker for differential dementia diagnosis.

Cerebrospinal fluid Aß1-40 improves differential dementia diagnosis in patients with intermediate P-tau181P levels.

It is assumed that the concentration of amyloid-ß1-40 (Aß1-40) in cerebrospinal fluid (CSF) reflects the total amount of Aß protein in the brain and thus allows a better interpretation of inter-individual differences in Aß quantity than the Aß1-42 concentration. In this study, Aß1-40 was added to the existing CSF biomarker panel of Aß1-42, total tau (T-tau), and phosphorylated tau (P-tau181P) in order to test whether the accuracy of the differential dementia diagnosis improved. The concentration of Aß1-40 (INNOTEST® ß-amyloid(1-40) prototype version, Innogenetics NV, Belgium) and the other biomarkers (INNOTEST®) was determined in CSF samples from 80 Alzheimer's disease (AD) patients, 75 non-AD dementia patients, and 30 controls. A large proportion of the study population had autopsy-confirmed neurodegeneration (AD: 73/80 = 91%; non-AD: 38/75 = 51%). The levels of Aß1-40 were decreased in AD (10856 ± 4745 pg/mL) and non-AD patients (10519 ± 4491 pg/mL) when compared to controls (14760 ± 7846 pg/mL) (p = 0.002 and p = 0.001). The Aß1-42/Aß1-40 ratio was significantly decreased in AD (0.043 ± 0.021) as compared to non-AD patients (0.064 ± 0.027; p < 0.001) and controls (0.053 ± 0.023; p < 0.001). In order to differentiate AD from non-AD patients, a decision tree was constructed. The diagnostic accuracy of the decision tree that contained Aß1-42, Aß1-40, P-tau181P, and the Aß1-42/Aß1-40 ratio was significantly better than the diagnostic accuracy (80% versus 74%) of the decision tree without Aß1-40 and the Aß1-42/Aß1-40 ratio (p < 0.001). In conclusion, no difference in Aß1-40 CSF levels was found between AD and non-AD patients, but adding CSF Aß1-40 and the CSF Aß1-42/Aß1-40 ratio to a biomarker-based decision tree, might have an added value for discriminating AD from non-AD patients in case of intermediate CSF P-tau181P values.

Amyloid pathology influences aß1-42 cerebrospinal fluid levels in dementia with lewy bodies.

A significant proportion of patients with dementia with Lewy bodies (DLB) show Alzheimer's disease (AD) pathology like senile plaques and neurofibrillary tangles. Biomarkers in cerebrospinal fluid (CSF), such as amyloid-ß1-42 (Aß1-42), total tau (T-tau), and hyperphosphorylated tau (P-tau181P), are linked to the different pathological hallmarks of AD. We set up a study to investigate the influence of AD co-pathology on CSF biomarker concentrations and profiles in autopsy-confirmed DLB. DLB patients with senile plaques showed significantly lower CSF Aß1-42 concentrations than DLB patients without senile plaques, but not compared to the AD patients. There were no significant differences in CSF T-tau or P-tau181P concentrations between DLB patients with and without neurofibrillary tangles. A correlation was found between the number of APOE ε4 alleles and Aß1-42 CSF levels in DLB patients with senile plaques. Although the CSF biomarkers Aß1-42, T-tau, and P-tau181P have an added diagnostic value for the differential dementia diagnosis, concomitant amyloid pathology in DLB limits the use of CSF Aß1-42 for the differential diagnosis of AD versus DLB.

Brain-specific tryptophan hydroxylase, TPH2, and 5-HTTLPR are associated with frontal lobe symptoms in Alzheimer's disease.

A prospective, longitudinal study was set up to investigate possible genetic associations of behavioral and psychological signs and symptoms of dementia (BPSD) in Alzheimer's disease (AD) with two candidate genes in the serotonergic neurotransmitter pathway: serotonin transporter (SLC6A4) and brain-specific tryptophan hydroxylase (TPH2). Patients with probable AD (n = 249) were diagnosed according to NINCDS/ADRDA criteria. During follow-up, autopsy-confirmation of clinical diagnosis was obtained in 32 AD patients. Taking into account follow-up behavioral assessments by means of validated behavioral assessment scales (Middelheim Frontality Score and Behave-AD), behavioral ratings reflecting the highest scores on any behavioral item ever observed since dementia onset were calculated and applied for statistical analyses. A functional insertion/deletion polymorphism in the promoter region of SLC6A4 (5-HTTLPR) and 10 selected SNPs within TPH2 were genotyped. Single-marker allelic association analyses (TPH2, 5-HTTLPR) were performed. TPH2 allelic analyses revealed significant associations with frontal lobe symptoms, as well as with diurnal rhythm disturbances. 5-HTTLPR S allele carriers had an increased risk to display loss of insight and judgment, another frontal lobe symptom. The present prospective, longitudinal study showed that mainly frontal lobe symptoms were significantly associated with TPH2 and 5-HTTLPR polymorphisms, pointing toward a role of the serotonergic neurotransmitter system in the pathophysiology of frontal lobe symptoms in AD.

Comparison of two analytical platforms for the clinical qualification of Alzheimer's disease biomarkers in pathologically-confirmed dementia.

Combined analysis of the Alzheimer's disease (AD) biomarkers amyloid-ß(1-42) (Aß(1-42)), total tau (T-tau), and hyperphosphorylated tau (P-tau(181P)) in cerebrospinal fluid (CSF) reduces the uncertainty associated with clinical dementia diagnosis. The present study evaluated the diagnostic accuracy of the CSF biomarker concentrations obtained with a multi-analyte Luminex assay (INNO-BIA AlzBio3) in comparison to single-analyte ELISA tests (INNOTEST). Data from 66 pathologically-confirmed dementia patients (51 AD and 15 non-AD) and 95 controls were included. Cut-off values were determined for each individual biomarker determined using both methods for different diagnostic challenges (dementia-controls; AD-controls; AD-non-AD). Comparing the diagnostic accuracy of individual cut-off values between INNO-BIA and INNOTEST, no relevant differences could be identified. Logistic regression was used in addition to identify the best combination of predictor variables (biomarkers). Discrimination of dementia patients from controls using Aß(1-42) and T-tau yielded a diagnostic accuracy of 0.87 and 0.90 for INNO-BIA and INNOTEST, respectively. Discriminating AD patients from controls, the diagnostic accuracy was 0.90 and 0.93 for INNO-BIA and INNOTEST, respectively. Optimal discrimination of AD and non-AD patients was achieved by combining Aß(1-42) and P-tau(181P) (diagnostic accuracy = 0.86). In conclusion, which AD biomarkers or combination thereof are most informative is dependent on the differential diagnosis, but the clinical value of these markers in each of the differential diagnoses is independent of the method by which concentrations are determined. Since the clinical value of the ELISA (INNOTEST) and Luminex (INNO-BIA) tests is comparable, further research to select the most suitable analytical platform for routine CSF biomarker measurements is needed.

Longitudinal stability of cerebrospinal fluid biomarker levels: fulfilled requirement for pharmacodynamic markers in Alzheimer's disease.

The current treatment for Alzheimer's disease (AD) is purely symptomatic, but medications interfering with underlying pathophysiological processes are being developed. To evaluate a possible disease-modifying effect, cerebrospinal fluid (CSF) biomarkers with a direct link to the underlying pathophysiology, such as amyloid-ß(1-42) (Aß(1-42)), total tau protein (T-tau), and hyperphosphorylated tau (P-tau(181P)), may play an important role. If intra-individual fluctuations in biomarker levels are small, the difference between two samples could serve as a pharmacodynamic measure. The aim of this study was to evaluate the longitudinal stability of CSF Aß(1-42), T-tau, and P-tau(181P) levels in AD patients and control subjects. Serial CSF samples of 28 AD patients and 23 controls with a minimum time interval of 30 days were included in this study. Serial CSF samples from 10 progressive patients (7 mild cognitive impairment (MCI) patients and 3 controls progressing to MCI or AD) were also analyzed. Intra-individual CSF Aß(1-42) and P-tau(181P) levels were stable in AD and controls. Intra-individual CSF T-tau levels differed significantly in AD patients, but not in controls. Change in biomarker concentrations per time unit was also significant between groups, but not within groups. The difference in biomarker levels in samples from progressive patients was not significant. In conclusion, CSF levels of Aß(1-42), T-tau, and P-tau(181P) are relatively stable over time. Only T-tau increased in AD patients in comparison to controls, which does not preclude its use as a diagnostic marker, nor as a potential pharmacodynamic marker.

Behavioral correlates of cerebrospinal fluid amino acid and biogenic amine neurotransmitter alterations in dementia.

BACKGROUND: Behavioral and psychological signs and symptoms of dementia (BPSD) are a heterogeneous group of behavioral and psychiatric disturbances occurring in dementia patients of any etiology. Research suggests that altered activities of dopaminergic, serotonergic, (nor)adrenergic, as well as amino acid neurotransmitter systems play a role in the etiopathogenesis of BPSD. In this study we attempted to identify cerebrospinal fluid (CSF) neurochemical correlates of BPSD to provide further insight into its underlying neurochemical pathophysiological mechanisms. METHODS: Patients with probable Alzheimer's disease (AD; n = 202), probable AD with cerebrovascular disease (n = 37), probable frontotemporal dementia (FTD; n = 32), and probable dementia with Lewy bodies (DLB; n = 26) underwent behavioral assessment and lumbar puncture. CSF levels of six amino acids and several biogenic amines and metabolites were analyzed using ultraperformance liquid chromatography with fluorescence detection and reversed-phase high-performance liquid chromatography with fluorescence detection. RESULTS: In the AD patients, CSF homovanillic acid/5-hydroxyindoleacetic acid (HVA/5HIAA) ratios correlated positively with anxieties/phobias, whereas CSF levels of taurine correlated negatively with depression and behavioral disturbances in general. In FTD patients, CSF levels of glutamate correlated negatively with verbally agitated behavior. In DLB patients, CSF levels of HVA correlated negatively with hallucinations. CONCLUSIONS: Several neurotransmitter systems can be linked to one specific behavioral syndrome depending on the dementia subtype. In addition to biogenic amines and metabolites, amino acids seem to play a major role in the neurochemical etiology of BPSD as well.

Prevalence and associated behavioral symptoms of depression in mild cognitive impairment and dementia due to Alzheimer's disease.

BACKGROUND: Mild cognitive impairment (MCI) is a clinical concept that categorizes subjects who are in an intermediate cognitive state between normal aging and dementia. The aims of this study are to determine the prevalence of significant depressive symptoms in MCI and Alzheimer's disease (AD) patients and to characterize the behavior associated with significant depressive symptoms in MCI and AD patients. METHODS: A cross-sectional analysis of baseline data from a prospective, longitudinal study on behavioral symptoms of dementia and MCI was performed. The study population consisted of 270 MCI and 402 AD patients. Behavioral assessment was performed by means of Middelheim Frontality Score, Behavioral Pathology in Alzheimer's Disease Rating Scale (Behave-AD) and Cohen-Mansfield Agitation Inventory. The presence of significant depressive symptoms was defined as a Cornell Scale for Depression in Dementia total score >7. RESULTS: The prevalence of significant depressive symptoms in AD patients (25%) was higher compared with MCI patients (16%) (p = 0.005). Patients with significant depressive symptoms showed an increased severity of frontal lobe symptoms, behavioral symptoms and agitation (Middelheim Frontality Score, Behave-AD and Cohen-Mansfield Agitation Inventory total scores; p < 0.001). Also, most of the individual frontal lobe and behavioral symptoms were more prevalent and severe, resulting in higher Behave-AD global scores. Mild cognitive impairment patients with depressive symptoms showed more severe behavioral symptoms and more severe verbally agitated behavior than AD patients without depressive symptoms (p < 0.001). CONCLUSIONS: Frontal lobe and behavioral symptoms are more prevalent and severe in MCI and AD patients with significant depressive symptoms as compared with patients without depressive symptoms.