Cerebrospinal fluid neurogranin concentration in neurodegeneration: relation to clinical phenotypes and neuropathology

Neurogranin (Ng) is a post-synaptic protein that previously has been shown to be a biomarker for synaptic function when measured in cerebrospinal fluid (CSF). The CSF concentration of Ng is increased in Alzheimer’s disease dementia (ADD), and even in the pre-dementia stage. In this prospective study, we used an enzyme-linked immunosorbent assay that quantifies Ng in CSF to test the performance of Ng as a marker of synaptic function. In 915 patients, CSF Ng was evaluated across several different neurodegenerative diseases. Of these 915 patients, 116 had a neuropathologically confirmed definitive diagnosis and the relation between CSF Ng and topographical distribution of different pathologies in the brain was evaluated. CSF Ng was specifically increased in ADD compared to eight other neurodegenerative diseases, including Parkinson’s disease (p < 0.0001), frontotemporal dementia (p < 0.0001), and amyotrophic lateral sclerosis (p = 0.0002). Similar results were obtained in neuropathologically confirmed cases. Using a biomarker index to evaluate whether CSF Ng contributed diagnostic information to the core AD CSF biomarkers (amyloid β (Aβ), t-tau, and p-tau), we show that Ng significantly increased the discrimination between AD and several other disorders. Higher CSF Ng levels were positively associated with greater Aβ neuritic plaque (Consortium to Establish a Registry for Alzheimer’s Disease (CERAD) neuritic plaque score, p = 0.0002) and tau tangle pathology (Braak neurofibrillary tangles staging, p = 0.0007) scores. In the hippocampus and amygdala, two brain regions heavily affected in ADD with high expression of Ng, CSF Ng was associated with plaque (p = 0.0006 and p < 0.0001), but not with tangle, α-synuclein, or TAR DNA-binding protein 43 loads. These data support that CSF Ng is increased specifically in ADD, that high CSF Ng concentrations likely reflect synaptic dysfunction and that CSF Ng is associated with β-amyloid plaque pathology.

Plasma neurofilament light as a potential biomarker of neurodegeneration in Alzheimer's disease

BACKGROUND

A growing body of evidence suggests that the plasma concentration of the neurofilament light chain (NfL) might be considered a plasma biomarker for the screening of neurodegeneration in Alzheimer's disease (AD).

METHODS

With a single molecule array method (Simoa, Quanterix), plasma NfL concentrations were measured in 99 subjects with AD at the stage of mild cognitive impairment (MCI-AD; n = 25) or at the stage of early dementia (ADD; n = 33), and in nondemented controls (n = 41); in all patients, the clinical diagnoses were in accordance with the results of the four core cerebrospinal fluid (CSF) biomarkers (amyloid β (Aβ)1-42, Aβ42/40, Tau, and pTau181), interpreted according to the Erlangen Score algorithm. The influence of preanalytical storage procedures on the NfL in plasma was tested on samples exposed to six different conditions.

RESULTS

NfL concentrations significantly increased in the samples exposed to more than one freezing/thawing cycle, and in those stored for 5 days at room temperature or at 4 °C. Compared with the control group of nondemented subjects (22.0 ± 12.4 pg/mL), the unadjusted plasma NfL concentration was highly significantly higher in the MCI-AD group (38.1 ± 15.9 pg/mL, p < 0.005) and even further elevated in the ADD group (49.1 ± 28.4 pg/mL; p < 0.001). A significant association between NfL and age (ρ = 0.65, p < 0.001) was observed; after correcting for age, the difference in NfL concentrations between AD and controls remained significant (p = 0.044). At the cutoff value of 25.7 pg/mL, unconditional sensitivity, specificity, and accuracy were 0.84, 0.78, and 0.82, respectively. Unadjusted correlation between plasma NfL and Mini Mental State Examination (MMSE) across all patients was moderate but significant (r = -0.49, p < 0.001). We observed an overall significant correlation between plasma NfL and the CSF biomarkers, but this correlation was not observed within the diagnostic groups.

CONCLUSIONS

This study confirms increased concentrations of plasma NfL in patients with Alzheimer's disease compared with nondemented controls.

Neurogranin as Cerebrospinal Fluid Biomarker for Alzheimer Disease: An Assay Comparison Study

BACKGROUND

Neurogranin in cerebrospinal fluid (CSF) correlates with cognitive decline and is a potential novel biomarker for Alzheimer disease (AD) dementia. We investigated the analytical and diagnostic performance of 3 commonly used neurogranin assays in the same cohort of patients to improve the interpretability of CSF neurogranin test results.

METHODS

The neurogranin Erenna® assay from Washington University, St. Louis, MO (WashU); ELISA from ADx Neurosciences; and ELISA from Gothenburg University, Mölndal, Sweden (UGot), were compared using silver staining and Western blot after gel electrophoresis. Clinical performance of the 3 assays was compared in samples from individuals diagnosed with subjective cognitive decline (n = 22), and in patients with AD (n = 22), frontotemporal dementia (n = 22), dementia with Lewy bodies (n = 22), or vascular dementia (n = 20), adjusted for sex and age.

RESULTS

The assays detected different epitopes of neurogranin: the WashU assay detected the N-terminal part of neurogranin (S10-D23) and a C-terminal part (G49-G60), the ADx assay detected C-terminal neurogranin truncated at P75, and the UGot assay detected the C-terminal neurogranin with intact ending (D78). Spearman ρ was 0.95 between ADx and WashU, 0.87 between UGot and WashU, and 0.81 between UGot and ADx. ANCOVA (analysis of covariance) showed group differences for ranked neurogranin concentrations in each assay (all P &lt; 0.05), with specific increases in AD.

CONCLUSIONS

Although the 3 assays target different epitopes on neurogranin and have different calibrators, the high correlations and the similar group differences suggest that the different forms of neurogranin in CSF carry similar diagnostic information, at least in the context of neurodegenerative diseases.

Cerebrospinal fluid and blood biomarkers for neurodegenerative dementias: An update of the Consensus of the Task Force on Biological Markers in Psychiatry of the World Federation of Societies of Biological Psychiatry

In the 12 years since the publication of the first Consensus Paper of the WFSBP on biomarkers of neurodegenerative dementias, enormous advancement has taken place in the field, and the Task Force takes now the opportunity to extend and update the original paper. New concepts of Alzheimer's disease (AD) and the conceptual interactions between AD and dementia due to AD were developed, resulting in two sets for diagnostic/research criteria. Procedures for pre-analytical sample handling, biobanking, analyses and post-analytical interpretation of the results were intensively studied and optimised. A global quality control project was introduced to evaluate and monitor the inter-centre variability in measurements with the goal of harmonisation of results. Contexts of use and how to approach candidate biomarkers in biological specimens other than cerebrospinal fluid (CSF), e.g. blood, were precisely defined. Important development was achieved in neuroimaging techniques, including studies comparing amyloid-β positron emission tomography results to fluid-based modalities. Similarly, development in research laboratory technologies, such as ultra-sensitive methods, raises our hopes to further improve analytical and diagnostic accuracy of classic and novel candidate biomarkers. Synergistically, advancement in clinical trials of anti-dementia therapies energises and motivates the efforts to find and optimise the most reliable early diagnostic modalities. Finally, the first studies were published addressing the potential of cost-effectiveness of the biomarkers-based diagnosis of neurodegenerative disorders.

Cerebrospinal fluid markers of extracellular matrix remodelling, synaptic plasticity and neuroinflammation before and after cranial radiotherapy

BACKGROUND

Advances in the treatment of brain tumours have increased the number of long-term survivors, but at the cost of side effects following cranial radiotherapy ranging from neurocognitive deficits to outright tissue necrosis. At present, there are no tools reflecting the molecular mechanisms underlying such side effects, and thus no means to evaluate interventional effects after cranial radiotherapy. Therefore, fluid biomarkers are of great clinical interest.

OBJECTIVE

Cerebrospinal fluid (CSF) levels of proteins involved in inflammatory signalling, synaptic plasticity and extracellular matrix (ECM) integrity were investigated following radiotherapy to the brain.

METHODS

Patients with small-cell lung cancer (SCLC) eligible for prophylactic cranial irradiation (PCI) were asked to participate in the study. PCI was prescribed either as 2 Gy/fraction to a total dose of 30 Gy (limited disease) or 4 Gy/fraction to 20 Gy (extensive disease). CSF was collected by lumbar puncture at baseline, 3 months and 1 year following PCI. Protein concentrations were measured using immunobased assays or mass spectrometry.

RESULTS

The inflammatory markers IL-15, IL-16 and MCP-1/CCL2 were elevated in CSF 3 months following PCI compared to baseline. The plasticity marker GAP-43 was elevated 3 months following PCI, and the same trend was seen for SNAP-25, but not for SYT1. The investigated ECM proteins, brevican and neurocan, showed a decline following PCI. There was a strong correlation between the progressive decline of soluble APPα and brevican levels.

CONCLUSION

To our knowledge, this is the first time ECM-related proteins have been shown to be affected by cranial radiotherapy in patients with cancer. These findings may help us to get a better understanding of the mechanisms behind side effects following radiotherapy.

Prevalence of preclinical Alzheimer disease: Comparison of current classification systems

Objective

To determine the prevalence of preclinical Alzheimer disease (AD) according to current classification systems by examining CSF from a representative general population sample of 70-year-olds from Gothenburg, Sweden.

Method

The sample was derived from the population-based H70 Gothenburg Birth Cohort Studies in Gothenburg, Sweden. The participants (n = 322, age 70 years) underwent comprehensive neuropsychiatric, cognitive, and somatic examinations. CSF levels of β-amyloid (Aβ)₄₂, Aβ₄₀, total tau, and phosphorylated tau were measured. Preclinical AD was classified according to criteria of the A/T/N system, Dubois 2016, National Institute on Aging–Alzheimer's Association (NIA-AA) criteria, and International Working Group-2 (IWG-2) criteria. Individuals with Clinical Dementia Rating score >0 were excluded, leaving 259 cognitively unimpaired individuals.

Results

The prevalence of amyloid pathology was 22.8%, of total tau pathology was 33.2%, and of phosphorylated tau pathology was 6.9%. With the A/T/N system, the prevalence of A+/T−/N− was 13.1%, A+/T−/N+ was 7.3%, A+/T+/N+ was 2.3%, A−/T−/N+ was 18.9%, and A−/T+/N+ was 4.6%. When the Dubois criteria were applied, the prevalence of asymptomatic at risk for AD was 36.7% and of preclinical AD was 9.7%. With the NIA-AA criteria, the prevalence of stage 1 was 13.1% and stage 2 was 9.7%. With the IWG-2 criteria, the prevalence of asymptomatic at risk for AD was 9.7%. The APOE ε4 allele was associated with several of the categories. Men more often had total tau pathology, A+/T−/N+, preclinical AD according to Dubois 2016, asymptomatic at risk for AD according to the IWG-2 criteria, and NIA-AA stage 2.

Conclusion

The prevalence of pathologic AD markers was very common (46%) in a representative population sample of 70-year-olds. The clinical implications of these findings need to be scrutinized further in longitudinal studies.

Alzheimer's Disease-Associated Cerebrospinal Fluid (CSF) Biomarkers do not Correlate with CSF Volumes or CSF Production Rate

BACKGROUND

Neuropathologically, Alzheimer's disease (AD) is characterized by accumulation of a 42 amino acid peptide called amyloid-β (Aβ42) in extracellular senile plaques together with intraneuronal inclusions of hyperphosphorylated tau protein in neurofibrillary tangles and neuronal degeneration. These changes are reflected in the cerebrospinal fluid (CSF), the volumes and production rates of which vary considerably between individuals, by reduced concentration of Aβ42, increased concentration of phosphorylated tau (P-tau) protein, and increased concentration of total tau (T-tau) protein, respectively.

OBJECTIVE

To examine the outstanding question if CSF concentrations of AD associated biomarkers are influenced by variations in CSF volumes, CSF production rate, and intracranial pressure in healthy individuals.

METHODS

CSF concentrations of Aβ42, P-tau, and T-tau, as well as a number of other AD-related CSF biomarkers were analyzed together with intracranial subarachnoid, ventricular, and spinal CSF volumes, as assessed by magnetic resonance imaging volumetric measurements, and CSF production rate in 19 cognitively normal healthy subjects (mean age 70.6, SD 3.6 years).

RESULTS

Negative correlations were seen between the concentrations of three CSF biomarkers (albumin ratio, Aβ38, and Aβ40), and ventricular CSF volume, but apart from this finding, no significant correlations were observed.

CONCLUSION

These results speak against inter-individual variations in CSF volume and production rate as important confounds in the AD biomarker research field.

Central and peripheral leptin and agouti-related protein during and after pregnancy in relation to weight change

OBJECTIVE

To study changes of neuropeptides and adipokines in cerebrospinal fluid (CSF) and serum from pregnancy to postpregnancy in relation to weight changes, fat mass and glucose metabolism.

CONTEXT

With high postpartum weight retention being a risk factor in future pregnancies and of lifelong obesity, we evaluated neuropeptide and adipokine changes in women who either gained weight or were weight stable.

DESIGN

Women were followed for 5 ± 1 years after pregnancy and divided into two groups, weight stable and weight gain, by weight change from start of pregnancy.

PATIENTS

Twenty-five women (BMI 27 ± 5 kg/m² ) recruited at admission for elective caesarean section.

MEASUREMENTS

CSF and serum levels of agouti-related protein (AgRP), leptin and insulin, and serum levels of adiponectin and soluble leptin receptor were measured during and after pregnancy. These measurements were further related to fat mass and insulin sensitivity (HOMA-IR).

RESULTS

S-AgRP levels during pregnancy were lower in the weight stable group and a 1 unit increase in s-AgRP was associated with 24% higher odds of pertaining to the weight gain group. After pregnancy, s-AgRP increased in the weight stable group but decreased in the weight gain group. Decreased transport of leptin into CSF during pregnancy was reversed by an increased CSF:serum leptin ratio after pregnancy. In women who returned to their prepregnancy weight, serum adiponectin increased after pregnancy and correlated negatively with HOMA-IR.

CONCLUSION

S-AgRP concentration in late pregnancy may be one factor predicting weight change after pregnancy, and circulating AgRP may be physiologically important in the long-term regulation of body weight.

C3 deficiency ameliorates the negative effects of irradiation of the young brain on hippocampal development and learning

Radiotherapy in the treatment of pediatric brain tumors is often associated with debilitating late-appearing adverse effects, such as intellectual impairment. Areas in the brain harboring stem cells are particularly sensitive to irradiation (IR) and loss of these cells may contribute to cognitive deficits. It has been demonstrated that IR-induced inflammation negatively affects neural progenitor differentiation. In this study, we used mice lacking the third complement component (C3^−/−) to investigate the role of complement in a mouse model of IR-induced injury to the granule cell layer (GCL) of the hippocampus. C3^−/− and wild type (WT) mice received a single, moderate dose of 8 Gy to the brain on postnatal day 10. The C3^−/− mice displayed 55 % more microglia (Iba-1+) and a trend towards increase in proliferating cells in the GCL compared to WT mice 7 days after IR. Importantly, months after IR C3^−/− mice made fewer errors than WT mice in a reversal learning test indicating better learning capacity in C3^−/− mice after IR. Notably, months after IR C3^−/− and WT mice had similar GCL volumes, survival of newborn cells (BrdU), microglia (Iba-1) and astrocyte (S100β) numbers in the GCL. In summary, our data show that the complement system contributes to IR-induced loss of proliferating cells and maladaptive inflammatory responses in the acute phase after IR, leading to impaired learning capacity in adulthood. Targeting the complement system is hence promising for future strategies to reduce the long-term adverse consequences of IR in the young brain.

Plasma and cerebrospinal fluid tau and neurofilament concentrations in rapidly progressive neurological syndromes: a neuropathology-based cohort

BACKGROUND AND PURPOSE

Cerebrospinal fluid (CSF) tau and neurofilament light chain (NF-L) proteins have proved to be reliable biomarkers for neuronal damage; however, there is a strong need for blood-based tests.

METHODS

The present study included 132 autopsy cases with rapidly progressive neurological syndromes, including Alzheimer disease (AD) (21), sporadic (65) and genetic (21) Creutzfeldt-Jakob disease (CJD), 25 cases with vascular, neoplastic and inflammatory alterations, and additionally 18 healthy control individuals. CSF tau and NF-L concentrations were measured by enzyme-linked immunosorbent assay. Plasma tau and NF-L concentrations were measured using ultra-sensitive single molecule array technology.

RESULTS

Plasma and CSF tau (R = 0.59, P < 0.001) and NF-L (R = 0.69, P < 0.001) levels correlated significantly (Spearman test). Plasma tau and NF-L levels were significantly higher in all disease groups compared to healthy controls (P < 0.001). Receiver operating characteristic curves were used and area under the curve values for comparisons with controls were 0.82 (AD), 0.94 (sporadic CJD), 0.92 (genetic CJD) and 0.83 (other neurological disorders) for plasma tau and 0.99, 0.99, 1.00 and 0.96 for plasma NF-L, respectively. Molecular subtyping of sporadic CJD showed a strong effect (linear logistic regression) on plasma tau (P < 0.001) but not NF-L levels (P = 0.19).

CONCLUSION

Plasma tau and NF-L concentrations are strongly increased in CJD and show similar diagnostic performance to the corresponding CSF measure. Molecular subtypes of sporadic CJD show different levels of plasma tau. Although not disease-specific, these findings support the use of plasma tau and NF-L as tools to identify, or to rule out, neurodegeneration.

Association of Plasma Neurofilament Light With Neurodegeneration in Patients With Alzheimer Disease

Question

What is the importance of plasma neurofilament light in Alzheimer disease?

Findings

In this case-control study of 193 cognitively healthy controls, 197 patients with mild cognitive impairment, and 180 patients with Alzheimer disease dementia, plasma neurofilament light was associated with Alzheimer disease and correlated with future progression of cognitive decline, brain atrophy, and brain hypometabolism.

Meaning

Plasma neurofilament light may be a promising noninvasive biomarker for Alzheimer disease.

Importance

Existing cerebrospinal fluid (CSF) or imaging (tau positron emission tomography) biomarkers for Alzheimer disease (AD) are invasive or expensive. Biomarkers based on standard blood test results would be useful in research, drug development, and clinical practice. Plasma neurofilament light (NFL) has recently been proposed as a blood-based biomarker for neurodegeneration in dementias.

Objective

To test whether plasma NFL concentrations are increased in AD and associated with cognitive decline, other AD biomarkers, and imaging evidence of neurodegeneration.

Design, Setting, and Participants

In this prospective case-control study, an ultrasensitive assay was used to measure plasma NFL concentration in 193 cognitively healthy controls, 197 patients with mild cognitive impairment (MCI), and 180 patients with AD dementia from the Alzheimer’s Disease Neuroimaging Initiative. The study dates were September 7, 2005, to February 13, 2012. The plasma NFL analysis was performed in September 2016.

Main Outcomes and Measures

Associations were tested between plasma NFL and diagnosis, Aβ pathologic features, CSF biomarkers of neuronal injury, cognition, brain structure, and metabolism.

Results

Among 193 cognitively healthy controls, 197 patients with mild cognitive impairment, and 180 patients with AD with dementia, plasma NFL correlated with CSF NFL (Spearman ρ = 0.59, P < .001). Plasma NFL was increased in patients with MCI (mean, 42.8 ng/L) and patients with AD dementia (mean, 51.0 ng/L) compared with controls (mean, 34.7 ng/L) (P < .001) and had high diagnostic accuracy for patients with AD with dementia vs controls (area under the receiver operating characteristic curve, 0.87, which is comparable to established CSF biomarkers). Plasma NFL was particularly high in patients with MCI and patients with AD dementia with Aβ pathologic features. High plasma NFL correlated with poor cognition and AD-related atrophy (at baseline and longitudinally) and with brain hypometabolism (longitudinally).

Conclusions and Relevance

Plasma NFL is associated with AD diagnosis and with cognitive, biochemical, and imaging hallmarks of the disease. This finding implies a potential usefulness for plasma NFL as a noninvasive biomarker in AD.

Reduced cerebrospinal fluid concentration of interleukin-12/23 subunit p40 in patients with cognitive impairment

Background

The role of inflammation in Alzheimer’s disease (AD) and other cognitive disorders is unclear. In a well-defined mono-center population, we measured cytokines and chemokines in paired serum and cerebrospinal fluid (CSF) samples.

Methods

Consecutive patients with AD (n = 30), stable mild cognitive impairment (SMCI, n = 11), other dementias (n = 11), and healthy controls (n = 18) were included. None of the subjects was treated with glucocorticoids, cholinesterase inhibitors, or non-steroidal anti-inflammatory drugs. Serum and CSF concentrations of interleukin-6 (IL-6), IL-8, IL-12/23 p40, IL-15, IL-16, vascular endothelial growth factor-A (VEGF-A), and three chemokines were measured using a multiplex panel.

Results

After correction for multiple comparisons, only CSF IL-12/23 p40 concentration differed significantly between the total patient group (n = 52) and controls (n = 18; p = 0.002). Further analyses showed that CSF IL-12/23 p40 concentration was decreased in all patient subgroups (AD, other dementias, and SMCI) compared to healthy controls (p < 0.01, p < 0.05, and p < 0.05, respectively). In the total study population (n = 70), CSF IL-12/23 p40 concentrations correlated positively with CSF concentrations of β-amyloid_1-42 (Aβ_1–42) and phosphorylated tau protein (P-tau) whereas in AD patients (n = 30), CSF IL-12/23 p40 only correlated positively with CSF P-Tau (r = 0.46, p = 0.01).

Conclusions

Most cytokines and chemokines were similar in patients and controls, but CSF IL-12/23 subunit p40 concentration was decreased in patients with cognitive impairment, and correlated with markers of AD disease status. Further studies are needed to evaluate the role of CSF IL-12/23 p40 in other dementias and SMCI.

The influence of insulin resistance on cerebrospinal fluid and plasma biomarkers of Alzheimer's pathology

Background

Insulin resistance (IR) has previously been associated with an increased risk of developing Alzheimer’s disease (AD), although the relationship between IR and AD is not yet clear. Here, we examined the influence of IR on AD using plasma and cerebrospinal fluid (CSF) biomarkers related to IR and AD in cognitively healthy men. We also aimed to characterise the shared protein signatures between IR and AD.

Methods

Fifty-eight cognitively healthy men, 28 IR and 30 non-IR (age and APOE ε4 matched), were drawn from the Metabolic Syndrome in Men study in Kuopio, Finland. CSF AD biomarkers (amyloid β-peptide (Aβ), total tau and tau phosphorylated at the Thr181 epitope) were examined with respect to IR. Targeted proteomics using ELISA and Luminex xMAP assays were performed to assess the influence of IR on previously identified CSF and plasma protein biomarker candidates of AD pathology. Furthermore, CSF and plasma SOMAscan was performed to discover proteins that associate with IR and CSF AD biomarkers.

Results

CSF AD biomarkers did not differ between IR and non-IR groups, although plasma insulin correlated with CSF Aβ/tau across the whole cohort. In total, 200 CSF and 487 plasma proteins were differentially expressed between IR and non-IR subjects, and significantly enriched pathways, many of which have been previously implicated in AD, were identified. CSF and plasma proteins significantly associated with CSF AD biomarkers were also discovered, and those sensitive to both IR and AD were identified.

Conclusions

These data indicate that IR is not directly related to the level of CSF AD pathology in cognitively healthy men. Proteins that associated with both AD and IR are potential markers indicative of shared pathology.

Electronic supplementary material

The online version of this article (doi:10.1186/s13195-017-0258-6) contains supplementary material, which is available to authorized users.

Comparison of three analytical platforms for quantification of the neurofilament light chain in blood samples: ELISA, electrochemiluminescence immunoassay and Simoa

BACKGROUND

Neuronal damage is the morphological substrate of persisting neurological disability. Neurofilaments (Nf) are specific cytoskeletal proteins of neurons and their quantification has shown encouraging results as a biomarker for axonal injury.

METHODS

We aimed at comparing a widely used conventional ELISA for Nf light chain (NfL) with an electrochemiluminescence-based method (ECL assay) and a newly developed single-molecule array (Simoa) method in clinically relevant cerebrospinal fluid (CSF) and serum samples.

RESULTS

Analytical sensitivity was 0.62 pg/mL for Simoa, 15.6 pg/mL for the ECL assay, and 78.0 pg/mL for the ELISA. Correlations between paired CSF and serum samples were strongest for Simoa (r=0.88, p<0.001) and the ECL assay (r=0.78, p<0.001) and weaker for ELISA measurements (r=0.38, p=0.030). CSF NfL measurements between the platforms were highly correlated (r=1.0, p<0.001). Serum NfL levels were highly related between ECL assay and Simoa (r=0.86, p<0.001), and this was less visible between ELISA-ECL assay (r=0.41, p=0.018) and ELISA-Simoa (r=0.43, p=0.013). Multiple sclerosis (MS) patients had significantly higher serum NfL levels than controls when measured with Simoa (p=0.001) but not with the other platforms.

CONCLUSIONS

We found Simoa to be more sensitive than ELISA or the ECL assay. Our results support the feasibility of quantifying NfL in serum; the results correlate with the more-established CSF NfL test. The highly sensitive Simoa technology deserves further studies in larger patient cohorts to clarify whether serum NfL could be used in the future to measure disease severity and determine prognosis or response to treatment interventions in neurological diseases.

Cerebrospinal fluid markers of neuronal and glial cell damage in patients with autoimmune neurologic syndromes with and without underlying malignancies

Autoimmune neurologic syndromes can be paraneoplastic (associated with malignancies and/or onconeural antibodies), or non-paraneoplastic. Their clinical presentation is often similar. As prognosis is related to malignancy treatment, better biomarkers are needed to identify patients with malignancy. We investigated cerebrospinal fluid (CSF) markers of neuronal (neurofilament light chain, NFL and total tau protein, T-tau) and glial (glial fibrillary acidic protein) damage. CSF-NFL and T-tau were increased in both paraneoplastic and non-paraneoplastic autoimmune syndromes. Patients with manifest malignancies were older, had less epilepsy, more focal central and peripheral neurological signs and symptoms, and worse long-term outcome, than those without malignancy. CSF-NFL-levels predicted long-term outcome but were not diagnostic for malignancy, after age adjustment.

Blood-based NfL: A biomarker for differential diagnosis of parkinsonian disorder

OBJECTIVE

To determine if blood neurofilament light chain (NfL) protein can discriminate between Parkinson disease (PD) and atypical parkinsonian disorders (APD) with equally high diagnostic accuracy as CSF NfL, and can therefore improve the diagnostic workup of parkinsonian disorders.

METHODS

The study included 3 independent prospective cohorts: the Lund (n = 278) and London (n = 117) cohorts, comprising healthy controls and patients with PD, progressive supranuclear palsy (PSP), corticobasal syndrome (CBS), and multiple system atrophy (MSA), as well as an early disease cohort (n = 109) of patients with PD, PSP, MSA, or CBS with disease duration ≤3 years. Blood NfL concentration was measured using an ultrasensitive single molecule array (Simoa) method, and the diagnostic accuracy to distinguish PD from APD was investigated.

RESULTS

We found strong correlations between blood and CSF concentrations of NfL (ρ ≥ 0.73-0.84, p ≤ 0.001). Blood NfL was increased in patients with MSA, PSP, and CBS (i.e., all APD groups) when compared to patients with PD as well as healthy controls in all cohorts (p < 0.001). Furthermore, in the Lund cohort, blood NfL could accurately distinguish PD from APD (area under the curve [AUC] 0.91) with similar results in both the London cohort (AUC 0.85) and the early disease cohort (AUC 0.81).

CONCLUSIONS

Quantification of blood NfL concentration can be used to distinguish PD from APD. Blood-based NfL might consequently be included in the diagnostic workup of patients with parkinsonian symptoms in both primary care and specialized clinics.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that blood NfL levels discriminate between PD and APD.

Comparison of Different Matrices as Potential Quality Control Samples for Neurochemical Dementia Diagnostics

BACKGROUND

Assay-vendor independent quality control (QC) samples for neurochemical dementia diagnostics (NDD) biomarkers are so far commercially unavailable. This requires that NDD laboratories prepare their own QC samples, for example by pooling leftover cerebrospinal fluid (CSF) samples.

OBJECTIVE

To prepare and test alternative matrices for QC samples that could facilitate intra- and inter-laboratory QC of the NDD biomarkers.

METHODS

Three matrices were validated in this study: (A) human pooled CSF, (B) Aβ peptides spiked into human prediluted plasma, and (C) Aβ peptides spiked into solution of bovine serum albumin in phosphate-buffered saline. All matrices were tested also after supplementation with an antibacterial agent (sodium azide). We analyzed short- and long-term stability of the biomarkers with ELISA and chemiluminescence (Fujirebio Europe, MSD, IBL International), and performed an inter-laboratory variability study.

RESULTS

NDD biomarkers turned out to be stable in almost all samples stored at the tested conditions for up to 14 days as well as in samples stored deep-frozen (at - 80°C) for up to one year. Sodium azide did not influence biomarker stability. Inter-center variability of the samples sent at room temperature (pooled CSF, freeze-dried CSF, and four artificial matrices) was comparable to the results obtained on deep-frozen samples in other large-scale projects.

CONCLUSION

Our results suggest that it is possible to replace self-made, CSF-based QC samples with large-scale volumes of QC materials prepared with artificial peptides and matrices. This would greatly facilitate intra- and inter-laboratory QC schedules for NDD measurements.

Serum neurofilament light protein predicts clinical outcome in traumatic brain injury

Axonal white matter injury is believed to be a major determinant of adverse outcomes following traumatic brain injury (TBI). We hypothesized that measurement of neurofilament light protein (NF-L), a protein found in long white-matter axons, in blood samples, may serve as a suitable biomarker for neuronal damage in TBI patients. To test our hypotheses, we designed a study in two parts: i) we developed an immunoassay based on Single molecule array technology for quantification of NF-L in blood, and ii) in a proof-of-concept study, we tested our newly developed method on serial serum samples from severe TBI (sTBI) patients (n = 72) and controls (n = 35). We also compared the diagnostic and prognostic utility of NF-L with the established blood biomarker S100B. NF-L levels were markedly increased in sTBI patients compared with controls. NF-L at admission yielded an AUC of 0.99 to detect TBI versus controls (AUC 0.96 for S100B), and increased to 1.00 at day 12 (0.65 for S100B). Importantly, initial NF-L levels predicted poor 12-month clinical outcome. In contrast, S100B was not related to outcome. Taken together, our data suggests that measurement of serum NF-L may be useful to assess the severity of neuronal injury following sTBI.

A targeted proteomic multiplex CSF assay identifies increased malate dehydrogenase and other neurodegenerative biomarkers in individuals with Alzheimer's disease pathology

Alzheimer's disease (AD) is the most common cause of dementia. Biomarkers are required to identify individuals in the preclinical phase, explain phenotypic diversity, measure progression and estimate prognosis. The development of assays to validate candidate biomarkers is costly and time-consuming. Targeted proteomics is an attractive means of quantifying novel proteins in cerebrospinal and other fluids, and has potential to help overcome this bottleneck in biomarker development. We used a previously validated multiplexed 10-min, targeted proteomic assay to assess 54 candidate cerebrospinal fluid (CSF) biomarkers in two independent cohorts comprising individuals with neurodegenerative dementias and healthy controls. Individuals were classified as 'AD' or 'non-AD' on the basis of their CSF T-tau and amyloid Aβ1-42 profile measured using enzyme-linked immunosorbent assay; biomarkers of interest were compared using univariate and multivariate analyses. In all, 35/31 individuals in Cohort 1 and 46/36 in Cohort 2 fulfilled criteria for AD/non-AD profile CSF, respectively. After adjustment for multiple comparisons, five proteins were elevated significantly in AD CSF compared with non-AD CSF in both cohorts: malate dehydrogenase; total APOE; chitinase-3-like protein 1 (YKL-40); osteopontin and cystatin C. In an independent multivariate orthogonal projection to latent structures discriminant analysis (OPLS-DA), these proteins were also identified as major contributors to the separation between AD and non-AD in both cohorts. Independent of CSF Aβ1-42 and tau, a combination of these biomarkers differentiated AD and non-AD with an area under curve (AUC)=0.88. This targeted proteomic multiple reaction monitoring (MRM)-based assay can simultaneously and rapidly measure multiple candidate CSF biomarkers. Applying this technique to AD we demonstrate differences in proteins involved in glucose metabolism and neuroinflammation that collectively have potential clinical diagnostic utility.

Plasma tau in Alzheimer disease

Objective:

To test whether plasma tau is altered in Alzheimer disease (AD) and whether it is related to changes in cognition, CSF biomarkers of AD pathology (including β-amyloid [Aβ] and tau), brain atrophy, and brain metabolism.

Methods:

This was a study of plasma tau in prospectively followed patients with AD (n = 179), patients with mild cognitive impairment (n = 195), and cognitive healthy controls (n = 189) from the Alzheimer's Disease Neuroimaging Initiative (ADNI) and cross-sectionally studied patients with AD (n = 61), mild cognitive impairment (n = 212), and subjective cognitive decline (n = 174) and controls (n = 274) from the Biomarkers for Identifying Neurodegenerative Disorders Early and Reliably (BioFINDER) study at Lund University, Sweden. A total of 1284 participants were studied. Associations were tested between plasma tau and diagnosis, CSF biomarkers, MRI measures, ¹⁸fluorodeoxyglucose-PET, and cognition.

Results:

Higher plasma tau was associated with AD dementia, higher CSF tau, and lower CSF Aβ₄₂, but the correlations were weak and differed between ADNI and BioFINDER. Longitudinal analysis in ADNI showed significant associations between plasma tau and worse cognition, more atrophy, and more hypometabolism during follow-up.

Conclusions:

Plasma tau partly reflects AD pathology, but the overlap between normal aging and AD is large, especially in patients without dementia. Despite group-level differences, these results do not support plasma tau as an AD biomarker in individual people. Future studies may test longitudinal plasma tau measurements in AD.

Reference measurement procedure for CSF amyloid beta (Aβ)1-42 and the CSF Aβ1-42 /Aβ1-40 ratio - a cross-validation study against amyloid PET

A clinical diagnosis of Alzheimer's disease is currently made on the basis of results from cognitive tests in combination with medical history and general clinical evaluation, but the peptide amyloid-beta (Aβ) in cerebrospinal fluid (CSF) is increasingly used as a biomarker for amyloid pathology in clinical trials and in recently proposed revised clinical criteria for Alzheimer's disease. Recent analytical developments have resulted in mass spectrometry (MS) reference measurement procedures for absolute quantification of Aβ_1-42 in CSF. The CSF Aβ_1-42 /Aβ_1-40 ratio has been suggested to improve the detection of cerebral amyloid deposition, by compensating for inter-individual variations in total Aβ production. Our aim was to cross-validate the reference measurement procedure as well as the Aβ_1-42 /Aβ_1-40 and Aβ_1-42 /Aβ_1-38 ratios in CSF, measured by high-resolution MS, with the cortical level of Aβ fibrils as measured by amyloid (¹⁸ F-flutemetamol) positron emission tomography (PET). We included 100 non-demented patients with cognitive symptoms from the Swedish BioFINDER study, all of whom had undergone both lumbar puncture and ¹⁸ F-flutemetamol PET. Comparing CSF Aβ_1-42 concentrations with ¹⁸ F-flutemetamol PET showed high concordance with an area under the receiver operating characteristic curve of 0.85 and a sensitivity and specificity of 82% and 81%, respectively. The ratio of Aβ_1-42 /Aβ_1-40 or Aβ_1-42 /Aβ_1-38 significantly improved concordance with an area under the receiver operating characteristic curve of 0.95 and a sensitivity and specificity of 96% and 91%, respectively. These results show that the CSF Aβ_1-42 /Aβ_1-40 and Aβ_1-42 /Aβ_1-38 ratios using the described MS method are strongly associated with cortical Aβ fibrils measured by ¹⁸ F-flutemetamol PET.

Serum neurofilament light chain protein is a measure of disease intensity in frontotemporal dementia

OBJECTIVE

To investigate serum neurofilament light chain (NfL) concentrations in frontotemporal dementia (FTD) and to see whether they are associated with the severity of disease.

METHODS

Serum samples were collected from 74 participants (34 with behavioral variant FTD [bvFTD], 3 with FTD and motor neuron disease and 37 with primary progressive aphasia [PPA]) and 28 healthy controls. Twenty-four of the FTD participants carried a pathogenic mutation in C9orf72 (9), microtubule-associated protein tau (MAPT; 11), or progranulin (GRN; 4). Serum NfL concentrations were determined with the NF-Light kit transferred onto the single-molecule array platform and compared between FTD and healthy controls and between the FTD clinical and genetic subtypes. We also assessed the relationship between NfL concentrations and measures of cognition and brain volume.

RESULTS

Serum NfL concentrations were higher in patients with FTD overall (mean 77.9 pg/mL [SD 51.3 pg/mL]) than controls (19.6 pg/mL [SD 8.2 pg/mL]; p < 0.001). Concentrations were also significantly higher in bvFTD (57.8 pg/mL [SD 33.1 pg/mL]) and both the semantic and nonfluent variants of PPA (95.9 and 82.5 pg/mL [SD 33.0 and 33.8 pg/mL], respectively) compared with controls and in semantic variant PPA compared with logopenic variant PPA. Concentrations were significantly higher than controls in both the C9orf72 and MAPT subgroups (79.2 and 40.5 pg/mL [SD 48.2 and 20.9 pg/mL], respectively) with a trend to a higher level in the GRN subgroup (138.5 pg/mL [SD 103.3 pg/mL). However, there was variability within all groups. Serum concentrations correlated particularly with frontal lobe atrophy rate (r = 0.53, p = 0.003).

CONCLUSIONS

Increased serum NfL concentrations are seen in FTD but show wide variability within each clinical and genetic group. Higher concentrations may reflect the intensity of the disease in FTD and are associated with more rapid atrophy of the frontal lobes.

Cerebrospinal fluid-induced retardation of amyloid β aggregation correlates with Alzheimer's disease and the APOE ε4 allele

Misfolding and aggregation of amyloid β (Aβ) are key features of Alzheimer's disease (AD) pathogenesis, but the molecular events controlling this process are not known in detail. In vivo, Aβ aggregation and plaque formation occur in the interstitial fluid of the brain extracellular matrix. This fluid communicates freely with cerebrospinal fluid (CSF). Here, we examined the effect of human CSF on Aβ aggregation kinetics in relation to AD diagnosis and carrier status of the apolipoprotein E (APOE) ε4 allele, the main genetic risk factor for sporadic AD. The aggregation of Aβ was inhibited in the presence of CSF and, surprisingly, the effect was more pronounced in APOE ε4 carriers. However, by fractionation of CSF using size exclusion chromatography, it became evident that it was not the ApoE protein itself that conveyed the inhibition, since the retarding species eluted at lower volume, corresponding to a much higher molecular weight, than ApoE monomers. Cholesterol quantification and immunoblotting identified high-density lipoprotein particles in the retarding fractions, indicating that such particles may be responsible for the inhibition. These results add information to the yet unresolved puzzle on how the risk factor of APOE ε4 functions in AD pathogenesis.

No diurnal variation of classical and candidate biomarkers of Alzheimer's disease in CSF

Background

Cerebrospinal fluid (CSF) biomarkers have gained increasing importance in the diagnostic work-up of Alzheimer’s disease (AD). The core CSF biomarkers related to AD pathology (Aβ42, t-tau and p-tau) are currently used in CSF diagnostics, while candidate markers of amyloid metabolism (Aβ38, Aβ40, sAPPα, sAPPβ), synaptic loss (neurogranin), neuroinflammation (YKL-40), neuronal damage (VILIP-1) and genetic risk (apolipoprotein E) are undergoing evaluation. Diurnal fluctuation in the concentration of CSF biomarkers has been reported and may represent a preanalytical confounding factor in the laboratory diagnosis of AD. The aim of the present study was to investigate the diurnal variability of classical and candidate CSF biomarkers in a cohort of neurosurgical patients carrying a CSF drainage.

Method

Samples were collected from a cohort of 13 neurosurgical patients from either ventricular (n = 6) or lumbar (n = 7) CSF drainage at six time points during the day, 1–7 days following the neurosurgical intervention. Concentrations of the core biomarkers were determined by immunoassays.

Results

Although absolute values largely varied among subjects, none of the biomarkers showed significant diurnal variation. Site of drainage (lumbar vs. ventricular) did not influence this result. The different immunoassays used for tau and Aβ markers provided similar results.

Conclusion

Time of day at CSF collection does not ultimately affect the concentration levels of classical and candidate AD biomarkers. Similar trends were found when using different immunoassays, thus corroborating the consistency of the data.

Electronic supplementary material

The online version of this article (doi:10.1186/s13024-016-0130-3) contains supplementary material, which is available to authorized users.

Increased Cerebrospinal Fluid Levels of Ubiquitin Carboxyl-Terminal Hydrolase L1 in Patients with Alzheimer's Disease

BACKGROUND

Dysfunctions of the ubiquitin proteasome system (UPS), including the highly abundant neuronal enzyme ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1), and autophagy-related changes (lysosomal degradation) are implicated in several neurodegenerative disorders including Alzheimer's disease (AD).

METHOD

This study evaluated cerebrospinal fluid (CSF) levels of UCH-L1, protein deglycase (DJ-1), neuron-specific enolase (NSE), and tau phosphorylated at threonine 231 (P-tau231) in two independent patient and control cohorts. Cohort 1 included CSF samples from subjects having an AD biomarker profile (n = 10) or a control biomarker profile (n = 31), while cohort 2 was a monocenter clinical study including patients with AD (n = 32), mild cognitive impairment (n = 13), other dementias (n = 15), as well as cognitively healthy controls (n = 20).

RESULTS

UCH-L1 and P-tau231 were elevated in AD patients compared to controls in both cohorts. CSF levels of DJ-1 and NSE were unchanged in the AD group, whereas they were decreased in the group of other dementia compared to controls in the clinical study.

CONCLUSION

Our main findings support that the UPS pathway may be impaired in AD, and UCH-L1 may serve as an additional CSF biomarker for AD.

Increased Cerebrospinal Fluid Level of Insulin-like Growth Factor-II in Male Patients with Alzheimer's Disease

BACKGROUND

Insulin-like growth factor-II (IGF-II) is important for brain development. Although IGF-II is abundant also in adult life, little is known of the role of IGF-II in Alzheimer's disease (AD).

OBJECTIVE AND METHODS

This was a cross-sectional study of 60 consecutive patients under primary evaluation of cognitive impairment and 20 healthy controls. The patients had AD dementia or mild cognitive impairment (MCI) diagnosed with AD dementia upon follow-up (n = 32), stable MCI (SMCI, n = 13), or other dementias (n = 15). IGF-II, IGF-binding protein-1 (IGFBP-1), and IGFBP-2 were analyzed in serum and cerebrospinal fluid (CSF).

RESULTS

Levels of IGF-II, IGFBP-1, and IGFBP-2 were similar in all groups in the total study population. Gender-specific analyses showed that in men (n = 40), CSF IGF-II level was higher in AD compared to SMCI and controls (p <  0.01 and p <  0.05, respectively). Furthermore, CSF IGFBP-2 level was increased in AD men versus SMCI men (p <  0.01) and tended to be increased versus control men (p = 0.09). There were no between-group differences in women (n = 40). In the total study population (n = 80) as well as in men (n = 40), CSF levels of IGF-II and IGFBP-2 correlated positively with CSF levels of the AD biomarkers total-tau and phosphorylated tau protein.

CONCLUSION

In men, but not women, in the early stages of AD, CSF IGF-II level was elevated, and CSF IGFBP-2 level tended to be increased, compared to healthy controls.

Blood biomarkers indicate mild neuroaxonal injury and increased amyloid β production after transient hypoxia during breath-hold diving

OBJECTIVE

To determine whether transient hypoxia during breath-hold diving causes neuronal damage or dysfunction or alters amyloid metabolism as measured by certain blood biomarkers.

DESIGN

Sixteen divers competing in the national Swedish championship in breath-hold diving and five age-matched healthy control subjects were included. Blood samples were collected at baseline and over a course of 3 days where the divers competed in static apnea (STA), dynamic apnea without fins (DYN1) and dynamic apnea with fins (DYN2).

MAIN OUTCOMES

Biomarkers reflecting brain injury and amyloid metabolism were analysed in serum (S-100β, NFL) and plasma (T-tau, Aβ42) using immunochemical methods.

RESULTS

Compared to divers' baseline, Aβ42 increased after the first event of static apnea (p = 0.0006). T-tau increased (p = 0.001) in STA vs baseline and decreased after one of the dynamic events, DYN2 (p = 0.03). Further, T-tau correlated with the length of the apneic time during STA (ρ = 0.7226, p = 0.004) and during DYN1 (ρ = 0.66, p = 0.01).

CONCLUSION

The findings suggest that transient hypoxia may acutely increase the levels of Aβ42 and T-tau in plasma of healthy adults, further supporting that general hypoxia may cause mild neuronal dysfunction or damage and stimulate Aβ production.

Update on ultrasensitive technologies to facilitate research on blood biomarkers for central nervous system disorders

Most research on fluid biomarkers for central nervous system (CNS) disorders has so far been performed using cerebrospinal fluid (CSF) as the biomarker source. CSF has the advantage of being closer to the brain than serum or plasma with a relative enrichment of CNS-specific proteins that are present at very low concentrations in the blood and thus difficult to reliably quantify using standard immunochemical technologies. Recent technical breakthroughs in the field of ultrasensitive assays have started to change this. Here, we review the most established ultrasensitive quantitative technologies that are currently available to general biomarker laboratories and discuss their use in research on biomarkers for CNS disorders.

Low Circulating Acute Brain-Derived Neurotrophic Factor Levels Are Associated With Poor Long-Term Functional Outcome After Ischemic Stroke

BACKGROUND AND PURPOSE

Brain-derived neurotrophic factor (BDNF) plays important roles in brain plasticity and repair, and it influences stroke outcomes in animal models. Circulating BDNF concentrations are lowered in patients with traumatic brain injury, and low BDNF predicts poor recovery after this injury. We sought to investigate whether circulating concentrations of BDNF are altered in the acute phase of ischemic stroke and whether they are associated with short- or long-term functional outcome.

METHODS

Serum concentrations of BDNF were measured in the Sahlgrenska Academy Study on Ischemic Stroke. The main outcomes were modified Rankin Scale (mRS) good (mRS score of 0-2) versus poor (mRS score of 3-6) at 3 months and 2 years after stroke, and good (mRS score of 0-2) versus poor (mRS score of 3-5) at 7 years after stroke.

RESULTS

Acute concentrations of BDNF were significantly lower in ischemic stroke cases (n=491) compared with controls (n=513). BDNF concentrations were not significantly associated with 3-month outcome. However, patients with BDNF in the lowest tertile had an increased risk of experiencing a poor outcome both at 2-year and 7-year follow-up, and these associations were independent of vascular risk factors and stroke severity (odds ratio, 2.6; confidence intervals, 1.4-4.9; P=0.002 and odds ratio, 2.1; confidence intervals, 1.1-3.9; P=0.028, respectively).

CONCLUSIONS

Circulating concentrations of BDNF protein are lowered in the acute phase of ischemic stroke, and low levels are associated with poor long-term functional outcome. Further studies are necessary to confirm these associations and to determine the predictive value of BDNF in stroke outcomes.

Cerebrospinal fluid levels of insulin, leptin, and agouti-related protein in relation to BMI in pregnant women

OBJECTIVE

During pregnancy, metabolic interactions must be adapted, though neuroendocrine mechanisms for increased food intake are poorly understood. The objective of this study was to characterize differences in insulin, leptin, and agouti-related protein (AgRP) levels in serum and cerebrospinal fluid (CSF) in pregnant women with normal weight (NW) and pregnant women with overweight (OW) or obesity (OB). Placenta as a source for increased peripheral AgRP levels during pregnancy was also investigated.

METHODS

Women were recruited at admission for elective cesarean section. Insulin, AgRP, and leptin were measured in serum and CSF from 30 NW, 25 OW, and 21 OB at term. Serum during pregnancy and placenta at term were collected for further AgRP analysis.

RESULTS

Immunohistology showed placental production of AgRP and serum AgRP levels increased throughout pregnancy. CSF AgRP, leptin, and insulin levels were higher in OW and OB than NW. Serum leptin and insulin levels were higher and AgRP lower in OB than NW.

CONCLUSIONS

High serum AgRP levels might protect from the suppressive effects of leptin during pregnancy. Pregnant women with OB and OW might further be protected from the suppressive effect of leptin by high CSF AgRP levels. Evidence was found, for the first time, of human placental AgRP production mirrored by levels in the circulation.

CSF and blood biomarkers for the diagnosis of Alzheimer's disease: a systematic review and meta-analysis

BACKGROUND

Alzheimer's disease biomarkers are important for early diagnosis in routine clinical practice and research. Three core CSF biomarkers for the diagnosis of Alzheimer's disease (Aβ42, T-tau, and P-tau) have been assessed in numerous studies, and several other Alzheimer's disease markers are emerging in the literature. However, there have been no comprehensive meta-analyses of their diagnostic performance. We systematically reviewed the literature for 15 biomarkers in both CSF and blood to assess which of these were most altered in Alzheimer's disease.

METHODS

In this systematic review and meta-analysis, we screened PubMed and Web of Science for articles published between July 1, 1984, and June 30, 2014, about CSF and blood biomarkers reflecting neurodegeneration (T-tau, NFL, NSE, VLP-1, and HFABP), APP metabolism (Aβ42, Aβ40, Aβ38, sAPPα, and sAPPβ), tangle pathology (P-tau), blood-brain-barrier function (albumin ratio), and glial activation (YKL-40, MCP-1, and GFAP). Data were taken from cross-sectional cohort studies as well as from baseline measurements in longitudinal studies with clinical follow-up. Articles were excluded if they did not contain a cohort with Alzheimer's disease and a control cohort, or a cohort with mild cognitive impairment due to Alzheimer's disease and a stable mild cognitive impairment cohort. Data were extracted by ten authors and checked by two for accuracy. For quality assessment, modified QUADAS criteria were used. Biomarker performance was rated by random-effects meta-analysis based on the ratio between biomarker concentration in patients with Alzheimer's disease and controls (fold change) or the ratio between biomarker concentration in those with mild cognitive impariment due to Alzheimer's disease and those with stable mild cognitive impairment who had a follow-up time of at least 2 years and no further cognitive decline.

FINDINGS

Of 4521 records identified from PubMed and 624 from Web of Science, 231 articles comprising 15 699 patients with Alzheimer's disease and 13 018 controls were included in this analysis. The core biomarkers differentiated Alzheimer's disease from controls with good performance: CSF T-tau (average ratio 2·54, 95% CI 2·44-2·64, p<0·0001), P-tau (1·88, 1·79-1·97, p<0·0001), and Aβ42 (0·56, 0·55-0·58, p<0·0001). Differentiation between cohorts with mild cognitive impairment due to Alzheimer's disease and those with stable mild cognitive impairment was also strong (average ratio 0·67 for CSF Aβ42, 1·72 for P-tau, and 1·76 for T-tau). Furthermore, CSF NFL (2·35, 1·90-2·91, p<0·0001) and plasma T-tau (1·95, 1·12-3·38, p=0·02) had large effect sizes when differentiating between controls and patients with Alzheimer's disease, whereas those of CSF NSE, VLP-1, HFABP, and YKL-40 were moderate (average ratios 1·28-1·47). Other assessed biomarkers had only marginal effect sizes or did not differentiate between control and patient samples.

INTERPRETATION

The core CSF biomarkers of neurodegeneration (T-tau, P-tau, and Aβ42), CSF NFL, and plasma T-tau were strongly associated with Alzheimer's disease and the core biomarkers were strongly associated with mild cognitive impairment due to Alzheimer's disease. Emerging CSF biomarkers NSE, VLP-1, HFABP, and YKL-40 were moderately associated with Alzheimer's disease, whereas plasma Aβ42 and Aβ40 were not. Due to their consistency, T-tau, P-tau, Aβ42, and NFL in CSF should be used in clinical practice and clinical research.

FUNDING

Swedish Research Council, Swedish State Support for Clinical Research, Alzheimer's Association, Knut and Alice Wallenberg Foundation, Torsten Söderberg Foundation, Alzheimer Foundation (Sweden), European Research Council, and Biomedical Research Forum.

Serum erythropoietin and outcome after ischaemic stroke: a prospective study

OBJECTIVES

Erythropoietin (EPO), which is inversely associated with blood haemoglobin (Hb), exerts neuroprotective effects in experimental ischaemic stroke (IS). However, clinical treatment trials have so far been negative. Here, in patients with IS, we analysed whether serum EPO is associated with (1) initial stroke severity, (2) recovery and (3) functional outcome.

DESIGN

Prospective. Controls available at baseline.

SETTING

A Swedish hospital-initiated study with outpatient follow-up after 3 months.

PARTICIPANTS

Patients (n=600; 64% males, mean age 56 years, controls n=600) were included from the Sahlgrenska Academy Study on IS (SAHLSIS).

PRIMARY AND SECONDARY OUTCOME MEASURES

In addition to EPO and Hb, initial stroke severity was assessed by the Scandinavian Stroke Scale (SSS) and compared with SSS after 3 months (follow-up) as a measure of recovery. Functional outcome was evaluated using the modified Rankin Scale (mRS) at follow-up. Serum EPO and SSS were divided into quintiles in the multivariate regression analyses.

RESULTS

Serum EPO was 21% and 31% higher than in controls at the acute phase of IS and follow-up, respectively. In patients, acute serum EPO was 19.5% higher in severe versus mild IS. The highest acute EPO quintile adjusted for sex, age and Hb was associated with worse stroke severity quintile (OR 1.70, 95% CI 1.00 to 2.87), better stroke recovery quintile (OR 1.93, CI 1.09 to 3.41) and unfavourable mRS 3-6 (OR 2.59, CI 1.15 to 5.80). However, the fourth quintile of EPO increase (from acute to follow-up) was associated with favourable mRS 0-2 (OR 3.42, CI 1.46 to 8.03). Only the last association withstood full adjustment.

CONCLUSIONS

The crude associations between EPO and worse stroke severity and outcome lost significance after multivariate modelling. However, in patients in whom EPO increased, the association with favourable outcome remained after adjustment for multiple covariates.

Assessing the commutability of reference material formats for the harmonization of amyloid-β measurements

The cerebrospinal fluid (CSF) amyloid-β (Aβ42) peptide is an important biomarker for Alzheimer’s disease (AD). Variability in measured Aβ42 concentrations at different laboratories may be overcome by standardization and establishing traceability to a reference system. Candidate certified reference materials (CRMs) are validated herein for this purpose.

Commutability of 16 candidate CRM formats was assessed across five CSF Aβ42 immunoassays and one mass spectrometry (MS) method in a set of 48 individual clinical CSF samples. Promising candidate CRM formats (neat CSF and CSF spiked with Aβ42) were identified and subjected to validation across eight (Elecsys, EUROIMMUN, IBL, INNO-BIA AlzBio3, INNOTEST, MSD, Simoa, and Saladax) immunoassays and the MS method in 32 individual CSF samples. Commutability was evaluated by Passing-Bablok regression and the candidate CRM termed commutable when found within the prediction interval (PI). The relative distance to the regression line was assessed.

The neat CSF candidate CRM format was commutable for almost all method comparisons, except for the Simoa/MSD, Simoa/MS and MS/IBL where it was found just outside the 95% PI. However, the neat CSF was found within 5% relative distance to the regression line for MS/IBL, between 5% and 10% for Simoa/MS and between 10% and 15% for Simoa/MSD comparisons.

The neat CSF candidate CRM format was commutable for 33 of 36 method comparisons, only one comparison more than expected given the 95% PI acceptance limit. We conclude that the neat CSF candidate CRM can be used for value assignment of the kit calibrators for the different Aβ42 methods.

Neurogranin and YKL-40: independent markers of synaptic degeneration and neuroinflammation in Alzheimer's disease

Introduction

Neuroinflammation and synaptic degeneration are major neuropathological hallmarks in Alzheimer’s disease (AD). Neurogranin and YKL-40 in cerebrospinal fluid (CSF) are newly discovered markers indicating synaptic damage and microglial activation, respectively.

Methods

CSF samples from 95 individuals including 39 patients with AD dementia (AD-D), 13 with mild cognitive impairment (MCI) due to AD (MCI-AD), 29 with MCI not due to AD (MCI-o) and 14 patients with non-AD dementias (non-AD-D) were analyzed for neurogranin and YKL-40.

Results

Patients with dementia or MCI due to AD showed elevated levels of CSF neurogranin (p < 0.001 for AD-D and p < 0.05 for MCI-AD) and YKL-40 (p < 0.05 for AD-D and p = 0.15 for MCI-AD) compared to mildly cognitively impaired subjects not diagnosed with AD. CSF levels of neurogranin and YKL-40 did not differ between MCI not due to AD and non-AD dementias. In AD subjects no correlation between YKL-40 and neurogranin was found. The CSF neurogranin levels correlated moderately with tau and p-tau but not with Aβ₄₂ or the MMSE in AD samples. No relevant associations between YKL-40 and MMSE or the core AD biomarkers, Aβ₄₂, t-tau and p-tau were found in AD subjects.

Conclusions

Neurogranin and YKL-40 are promising AD biomarkers, independent of and complementary to the established core AD biomarkers, reflecting additional pathological changes in the course of AD.

Electronic supplementary material

The online version of this article (doi:10.1186/s13195-015-0161-y) contains supplementary material, which is available to authorized users.

Plasma Concentration of the Neurofilament Light Protein (NFL) is a Biomarker of CNS Injury in HIV Infection: A Cross-Sectional Study

Background

Cerebrospinal fluid (CSF) neurofilament light chain protein (NFL) is a sensitive marker of neuronal injury in a variety of neurodegenerative conditions, including the CNS dysfunction injury that is common in untreated HIV infection. However, an important limitation is the requirement for lumbar puncture. For this reason, a sensitive and reliable blood biomarker of CNS injury would represent a welcome advance in both clinical and research settings.

Methods

To explore whether plasma concentrations of NFL might be used to detect CNS injury in HIV infection, an ultrasensitive Single molecule array (Simoa) immunoassay was developed. Using a cross-sectional design, we measured NFL in paired CSF and plasma samples from 121 HIV-infected subjects divided into groups according to stage of their systemic disease, presence of overt HIV-associated dementia (HAD), and after antiretroviral treatment (ART)-induced viral suppression. HIV-negative controls were also examined.

Findings

Plasma and CSF NFL concentrations were very highly correlated (r = 0.89, P < 0.0001). While NFL was more than 50-fold lower plasma than CSF it was within the quantifiable range of the new plasma assay in all subjects, including the HIV negatives and the HIV positives with normal CSF NFL concentrations. The pattern of NFL changes were almost identical in plasma and CSF, both exhibiting similar age-related increases in concentrations along with highest values in HAD and substantial elevations in ART-naïve neuroasymptomatic subjects with low blood CD4⁺ T cells.

Interpretation

These results show that plasma NFL may prove a valuable tool to evaluate ongoing CNS injury in HIV infection that may be applied in the clinic and in research settings to assess the presence if active CNS injury. Because CSF NFL is also elevated in a variety of other CNS disorders, sensitive measures of plasma NFL may similarly prove useful in other settings.

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Plasma NFL is a sensitive marker of neuronal injury

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Plasma and CSF NFL concentrations were highly correlated

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Plasma NFL is useful to detect active axonal injury in treated and untreated HIV

A sensitive blood biomarker of neuronal injury has long been sought for. Here we describe an ultrasensitive quantification measurement of the axonal neurofilament light chain protein (NFL) in blood. We test this in the setting of HIV brain injury in which cerebrospinal fluid (CSF) NFL has been well characterized and noted to be a reliable biomarker of neuronal injury.

Blood and CSF NFL were highly correlated and measurement of plasma NFL was able to detect both severe and subclinical neuronal injury in HIV.

CSF NFL is elevated in a wide range of additional neurodegenerative settings, so the reported findings likely have broader implications, though this requires additional direct study.

Technical performance of a novel, fully automated electrochemiluminescence immunoassay for the quantitation of β-amyloid (1-42) in human cerebrospinal fluid

INTRODUCTION

Available assays for quantitation of the Alzheimer's disease (AD) biomarker amyloid-beta 1-42 (Aβ [1-42]) in cerebrospinal fluid demonstrate significant variability and lack of standardization to reference measurement procedures (RMPs). We report analytical performance data for the novel Elecsys β-amyloid (1-42) assay (Roche Diagnostics).

METHODS

Lot-to-lot comparability was tested using method comparison. Performance parameters were measured according to Clinical & Laboratory Standards Institute (CLSI) guidelines. The assay was standardized to a Joint Committee for Traceability in Laboratory Medicine (JCTLM) approved RMP.

RESULTS

Limit of quantitation was <11.28 pg/mL, and the assay was linear throughout the measuring range (200-1700 pg/mL). Excellent lot-to-lot comparability was observed (correlation coefficients [Pearson's r] >0.995; bias in medical decision area <2%). Repeatability coefficients of variation (CVs) were 1.0%-1.6%, intermediate CVs were 1.9%-4.0%, and intermodule CVs were 1.1%-3.9%. Estimated total reproducibility was 2.0%-5.1%. Correlation with the RMP was good (Pearson's r, 0.93).

DISCUSSION

The Elecsys β-amyloid (1-42) assay has high analytical performance that may improve biomarker-based AD diagnosis.

Dissecting IWG-2 typical and atypical Alzheimer's disease: insights from cerebrospinal fluid analysis

Pathobiological factors underlying phenotypic diversity in Alzheimer's disease (AD) are incompletely understood. We used an extended cerebrospinal fluid (CSF) panel to explore differences between "typical" with "atypical" AD and between amnestic, posterior cortical atrophy, logopenic aphasia and frontal variants. We included 97 subjects fulfilling International Working Group-2 research criteria for AD of whom 61 had "typical" AD and 36 "atypical" syndromes, and 30 controls. CSF biomarkers included total tau (T-tau), phosphorylated tau (P-tau), amyloid β1-42, amyloid βX-38/40/42, YKL-40, neurofilament light (NFL), and amyloid precursor proteins α and β. The typical and atypical groups were matched for age, sex, severity and rate of cognitive decline and had similar biomarker profiles, with the exception of NFL which was higher in the atypical group (p = 0.03). Sub-classifying the atypical group into its constituent clinical syndromes, posterior cortical atrophy was associated with the lowest T-tau [604.4 (436.8-675.8) pg/mL], P-tau (79.8 ± 21.8 pg/L), T-tau/Aβ1-42 ratio [2.3 (1.4-2.6)], AβX-40/X-42 ratio (22.1 ± 5.8) and rate of cognitive decline [1.9 (0.75-4.25) MMSE points/year]. Conversely, the frontal variant group had the highest levels of T-tau [1185.4 (591.7-1329.3) pg/mL], P-tau (116.4 ± 45.4 pg/L), T-tau/Aβ1-42 ratio [5.2 (3.3-6.9)] and AβX-40/X-42 ratio (27.9 ± 7.5), and rate of cognitive decline. Whilst on a group level IWG-2 "typical" and "atypical" AD share similar CSF profiles, which are very different from controls, atypical AD is a heterogeneous entity with evidence for subtle differences in amyloid processing and neurodegeneration between different clinical syndromes. These findings also have practical implications for the interpretation of clinical CSF biomarker results.

Cerebrospinal fluid neurogranin: relation to cognition and neurodegeneration in Alzheimer's disease

Synaptic dysfunction is linked to cognitive symptoms in Alzheimer's disease. Thus, measurement of synapse proteins in cerebrospinal fluid may be useful biomarkers to monitor synaptic degeneration. Cerebrospinal fluid levels of the postsynaptic protein neurogranin are increased in Alzheimer's disease, including in the predementia stage of the disease. Here, we tested the performance of cerebrospinal fluid neurogranin to predict cognitive decline and brain injury in the Alzheimer's Disease Neuroimaging Initiative study. An in-house immunoassay was used to analyse neurogranin in cerebrospinal fluid samples from a cohort of patients who at recruitment were diagnosed as having Alzheimer's disease with dementia (n = 95) or mild cognitive impairment (n = 173), as well as in cognitively normal subjects (n = 110). Patients with mild cognitive impairment were grouped into those that remained cognitively stable for at least 2 years (stable mild cognitive impairment) and those who progressed to Alzheimer's disease dementia during follow-up (progressive mild cognitive impairment). Correlations were tested between baseline cerebrospinal fluid neurogranin levels and baseline and longitudinal cognitive impairment, brain atrophy and glucose metabolism within each diagnostic group. Cerebrospinal fluid neurogranin was increased in patients with Alzheimer's disease dementia (P < 0.001), progressive mild cognitive impairment (P < 0.001) and stable mild cognitive impairment (P < 0.05) compared with controls, and in Alzheimer's disease dementia (P < 0.01) and progressive mild cognitive impairment (P < 0.05) compared with stable mild cognitive impairment. In the mild cognitive impairment group, high baseline cerebrospinal fluid neurogranin levels predicted cognitive decline as reflected by decreased Mini-Mental State Examination (P < 0.001) and increased Alzheimer's Disease Assessment Scale-cognitive subscale (P < 0.001) scores at clinical follow-up. In addition, high baseline cerebrospinal fluid neurogranin levels in the mild cognitive impairment group correlated with longitudinal reductions in cortical glucose metabolism (P < 0.001) and hippocampal volume (P < 0.001) at clinical follow-up. Furthermore, within the progressive mild cognitive impairment group, elevated cerebrospinal fluid neurogranin levels were associated with accelerated deterioration in Alzheimer's Disease Assessment Scale-cognitive subscale (β = 0.0017, P = 0.01). These data demonstrate that cerebrospinal fluid neurogranin is increased already at the early clinical stage of Alzheimer's disease and predicts cognitive deterioration and disease-associated changes in metabolic and structural biomarkers over time.

A Practical Guide to Immunoassay Method Validation

Biochemical markers have a central position in the diagnosis and management of patients in clinical medicine, and also in clinical research and drug development, also for brain disorders, such as Alzheimer’s disease. The enzyme-linked immunosorbent assay (ELISA) is frequently used for measurement of low-abundance biomarkers. However, the quality of ELISA methods varies, which may introduce both systematic and random errors. This urges the need for more rigorous control of assay performance, regardless of its use in a research setting, in clinical routine, or drug development. The aim of a method validation is to present objective evidence that a method fulfills the requirements for its intended use. Although much has been published on which parameters to investigate in a method validation, less is available on a detailed level on how to perform the corresponding experiments. To remedy this, standard operating procedures (SOPs) with step-by-step instructions for a number of different validation parameters is included in the present work together with a validation report template, which allow for a well-ordered presentation of the results. Even though the SOPs were developed with the intended use for immunochemical methods and to be used for multicenter evaluations, most of them are generic and can be used for other technologies as well.