General anesthesia in early childhood and possible association with autism: a population-based matched cohort study.

BACKGROUND: In experimental animal studies, exposure to general anesthesia in early childhood may results in changes in infant brain morphology and behavior, potentially leading to the development of autistic behaviors in the long-term. However, in clinical studies the role of exposure to general anesthesia in early childhood and the risk of autism is unknown. METHODS: This is a population-based cohort study including all children aged 0-5 years of age exposed to general anesthesia between 2001 and 2014 and a corresponding matched population without such an exposure. Propensity score calculation was based on 49 variables (including age of parents, malformations, APGAR Score, and family income, among others). Quasi-Poisson regression was used to estimate risk ratios (RRs) with 95% confidence intervals (CIs) for the association between exposure to general anesthesia and autism or autism spectrum disorder. RESULTS: In total, 401,750 children exposed to general anesthesia were compared with 1,187,796 unexposed individuals. Autism or autism spectrum disorder were more common in the children exposed to general anesthesia as compared to unexposed children (1.65% and 0.98%, respectively, P<0.01). There was a statistically significant higher risk of autism or autism spectrum disorder in children exposed to general anesthesia as compared to unexposed children also after propensity score adjustment (RR 1.62, 95% CI: 1.57-1.67). CONCLUSIONS: Exposure to general anesthesia in early childhood was associated with an increased risk of autism or autism spectrum disorder. Future studies are needed to asses if general anesthesia may cause autism or if the association is due to other factors.

Cerebrospinal fluid p-tau217 performs better than p-tau181 as a biomarker of Alzheimer's disease.

Cerebrospinal fluid (CSF) p-tau181 (tau phosphorylated at threonine 181) is an established biomarker of Alzheimer's disease (AD), reflecting abnormal tau metabolism in the brain. Here we investigate the performance of CSF p-tau217 as a biomarker of AD in comparison to p-tau181. In the Swedish BioFINDER cohort (n = 194), p-tau217 shows stronger correlations with the tau positron emission tomography (PET) tracer [18F]flortaucipir, and more accurately identifies individuals with abnormally increased [18F]flortaucipir retention. Furthermore, longitudinal increases in p-tau217 are higher compared to p-tau181 and better correlate with [18F]flortaucipir uptake. P-tau217 correlates better than p-tau181 with CSF and PET measures of neocortical amyloid-ß burden and more accurately distinguishes AD dementia from non-AD neurodegenerative disorders. Higher correlations between p-tau217 and [18F]flortaucipir are corroborated in an independent EXPEDITION3 trial cohort (n = 32). The main results are validated using a different p-tau217 immunoassay. These findings suggest that p-tau217 might be more useful than p-tau181 in the diagnostic work up of AD.

Blood phosphorylated tau 181 as a biomarker for Alzheimer's disease: a diagnostic performance and prediction modelling study using data from four prospective cohorts.

BACKGROUND: CSF and PET biomarkers of amyloid ß and tau accurately detect Alzheimer's disease pathology, but the invasiveness, high cost, and poor availability of these detection methods restrict their widespread use as clinical diagnostic tools. CSF tau phosphorylated at threonine 181 (p-tau181) is a highly specific biomarker for Alzheimer's disease pathology. We aimed to assess whether blood p-tau181 could be used as a biomarker for Alzheimer's disease and for prediction of cognitive decline and hippocampal atrophy. METHODS: We developed and validated an ultrasensitive blood immunoassay for p-tau181. Assay performance was evaluated in four clinic-based prospective cohorts. The discovery cohort comprised patients with Alzheimer's disease and age-matched controls. Two validation cohorts (TRIAD and BioFINDER-2) included cognitively unimpaired older adults (mean age 63-69 years), participants with mild cognitive impairment (MCI), Alzheimer's disease, and frontotemporal dementia. In addition, TRIAD included healthy young adults (mean age 23 years) and BioFINDER-2 included patients with other neurodegenerative disorders. The primary care cohort, which recruited participants in Montreal, Canada, comprised control participants from the community without a diagnosis of a neurological condition and patients referred from primary care physicians of the Canadian National Health Service for specialist care. Concentrations of plasma p-tau181 were compared with established CSF and PET biomarkers and longitudinal measurements using Spearman correlation, area under the curve (AUC), and linear regression analyses. FINDINGS: We studied 37 individuals in the discovery cohort, 226 in the first validation cohort (TRIAD), 763 in the second validation cohort (BioFINDER-2), and 105 in the primary care cohort (n=1131 individuals). In all cohorts, plasma p-tau181 showed gradual increases along the Alzheimer's disease continuum, from the lowest concentrations in amyloid ß-negative young adults and cognitively unimpaired older adults, through higher concentrations in the amyloid ß-positive cognitively unimpaired older adults and MCI groups, to the highest concentrations in the amyloid ß-positive MCI and Alzheimer's disease groups (p<0·001, Alzheimer's disease vs all other groups). Plasma p-tau181 distinguished Alzheimer's disease dementia from amyloid ß-negative young adults (AUC=99·40%) and cognitively unimpaired older adults (AUC=90·21-98·24% across cohorts), as well as other neurodegenerative disorders, including frontotemporal dementia (AUC=82·76-100% across cohorts), vascular dementia (AUC=92·13%), progressive supranuclear palsy or corticobasal syndrome (AUC=88·47%), and Parkinson's disease or multiple systems atrophy (AUC=81·90%). Plasma p-tau181 was associated with PET-measured cerebral tau (AUC=83·08-93·11% across cohorts) and amyloid ß (AUC=76·14-88·09% across cohorts) pathologies, and 1-year cognitive decline (p=0·0015) and hippocampal atrophy (p=0·015). In the primary care cohort, plasma p-tau181 discriminated Alzheimer's disease from young adults (AUC=100%) and cognitively unimpaired older adults (AUC=84·44%), but not from MCI (AUC=55·00%). INTERPRETATION: Blood p-tau181 can predict tau and amyloid ß pathologies, differentiate Alzheimer's disease from other neurodegenerative disorders, and identify Alzheimer's disease across the clinical continuum. Blood p-tau181 could be used as a simple, accessible, and scalable test for screening and diagnosis of Alzheimer's disease. FUNDING: Alzheimer Drug Discovery Foundation, European Research Council, Swedish Research Council, Swedish Alzheimer Foundation, Swedish Dementia Foundation, Alzheimer Society Research Program.

Perspectives in fluid biomarkers in neurodegeneration from the 2019 biomarkers in neurodegenerative diseases course-a joint PhD student course at University College London and University of Gothenburg.

Until relatively recently, a diagnosis of probable Alzheimer's disease (AD) and other neurodegenerative disorders was principally based on clinical presentation, with post-mortem examination remaining a gold standard for disease confirmation. This is in sharp contrast to other areas of medicine, where fluid biomarkers, such as troponin levels in myocardial infarction, form an integral part of the diagnostic and treatment criteria. There is a pressing need for such quantifiable and easily accessible tools in neurodegenerative diseases.In this paper, based on lectures given at the 2019 Biomarkers in Neurodegenerative Diseases Course, we provide an overview of a range of cerebrospinal fluid (CSF) and blood biomarkers in neurodegenerative disorders, including the 'core' AD biomarkers amyloid ß (Aß) and tau, as well as other disease-specific and general markers of neuroaxonal injury. We then highlight the main challenges in the field, and how those could be overcome with the aid of new methodological advances, such as assay automation, mass spectrometry and ultrasensitive immunoassays.As we hopefully move towards an era of disease-modifying treatments, reliable biomarkers will be essential to increase diagnostic accuracy, allow for earlier diagnosis, better participant selection and disease activity and treatment effect monitoring.

Plasma P-tau181 in Alzheimer's disease: relationship to other biomarkers, differential diagnosis, neuropathology and longitudinal progression to Alzheimer's dementia.

Plasma phosphorylated tau181 (P-tau181) might be increased in Alzheimer's disease (AD), but its usefulness for differential diagnosis and prognosis is unclear. We studied plasma P-tau181 in three cohorts, with a total of 589 individuals, including cognitively unimpaired participants and patients with mild cognitive impairment (MCI), AD dementia and non-AD neurodegenerative diseases. Plasma P-tau181 was increased in preclinical AD and further increased at the MCI and dementia stages. It correlated with CSF P-tau181 and predicted positive Tau positron emission tomography (PET) scans (area under the curve (AUC) = 0.87-0.91 for different brain regions). Plasma P-tau181 differentiated AD dementia from non-AD neurodegenerative diseases with an accuracy similar to that of Tau PET and CSF P-tau181 (AUC = 0.94-0.98), and detected AD neuropathology in an autopsy-confirmed cohort. High plasma P-tau181 was associated with subsequent development of AD dementia in cognitively unimpaired and MCI subjects. In conclusion, plasma P-tau181 is a noninvasive diagnostic and prognostic biomarker of AD, which may be useful in clinical practice and trials.

Acute reduction of cerebrospinal fluid volume prior to spinal anesthesia: implications for sensory block extent.

BACKGROUND: Multiple patient and clinical characteristics contribute to the variable outcome of spinal anesthesia (SPA). Acute reduction of cerebrospinal fluid (CSF) volume may alter the effect of SPA. The objective of the present study was to test if aspiration of 10 mL CSF immediately prior to SPA is associated with higher extent of sensory block. METHODS: Interventional cohort study. One hundred and two patients undergoing total hip arthroplasty (THA) were included. Fifty-one patients underwent sampling of 10 mL CSF prior to SPA (CSF aspiration group); 51 consecutive patients were used as controls. The primary outcome was the extent of sensory block to cold stimulus 20 minutes after injection of hyperbaric bupivacaine. Secondary outcome measures included duration of motor block and incidence of failed SPA. RESULTS: Acute reduction of CSF volume by 10 mL increased the extent of sensory anesthesia (mean thoracic level [T] 4.3±2.4 vs. 7.1±2.6, P<0.001). There were no significant between-group differences regarding motor block duration (P≥0.30) or failed SPA (three of 51 [CSF aspiration group] vs. one of 51 [control group], P=0.31). In a retrospective data analysis, 10 of 13 patients in the CSF aspiration group who had previously received SPA had a higher sensory block after 10 mL CSF aspiration compared to the previous SPA (T4.1 [range, 0-11] vs. T8.2 [4-10], P<0.01). CONCLUSIONS: Acute reduction of CSF volume by 10 mL prior to SPA leads to a higher thoracic level of sensory block.

Cerebrospinal fluid levels of neurogranin in Parkinsonian disorders.

BACKGROUND: CSF concentration of neurogranin has been suggested as a biomarker for synapse dysfunction. OBJECTIVES: To investigate CSF neurogranin in parkinsonian disorders compared to controls and Alzheimer's disease and the possible correlations between neurogranin and cognitive and motor impairment. METHODS: We included 157 patients with PD, 29 with PD with dementia, 11 with dementia with Lewy bodies, 26 with MSA, 21 with PSP, 6 with corticobasal syndrome, 47 controls, and 124 with Alzheimer's disease. CSF neurogranin was measured using two enzyme-linked immunosorbent assays; from EUROIMMUN and the University of Gothenburg. RESULTS: We found a strong correlation between CSF neurogranin-EI and CSF neurogranin-University of Gothenburg (Rs = 0.890; P < 0.001). Neurogranin was decreased in PD, PD with dementia, MSA, and PSP compared to controls and Alzheimer's disease. Neurogranin did not correlate with motor or cognitive impairment, longitudinal decline, or progression to dementia in PD. CONCLUSIONS: CSF neurogranin is decreased in parkinsonian disorders compared to controls, emphasizing the importance of synaptic dysfunction in these disorders. © 2019 International Parkinson and Movement Disorder Society.

Apathy and anxiety are early markers of Alzheimer's disease.

In this study, we investigated associations between neuropsychiatric symptoms (i.e., apathy, anxiety, and depression) and cerebral atrophy, white matter lesions (WML), beta-amyloid (Aß) deposition, and cognitive decline in a nondemented sample. 104 cognitively unimpaired and 53 subjects with mild cognitive impairment were followed for up to 4 years within the Swedish BioFINDER study. Neuropsychiatric assessments included the Hospital Anxiety and Depression Scale and the Apathy Evaluation Scale. Magnetic resonance imaging and 18F-flutemetamol-positron emission tomography quantified brain atrophy, WML, and Aß deposition. Mini-Mental State Examination assessed longitudinal global cognition. Regression analyses were used to test for associations. Apathy and anxiety were shown related to Aß deposition and predicted cognitive decline. Anxiety also interacted with amyloid status to predict faster cognitive deterioration. Apathy was further related to frontotemporal and subcortical atrophy, as well as WML. To conclude, the associations between apathy and anxiety with Aß deposition and cognitive decline point to these symptoms as early clinical manifestations of Alzheimer's disease.

Predicting clinical decline and conversion to Alzheimer's disease or dementia using novel Elecsys Aß(1-42), pTau and tTau CSF immunoassays.

We evaluated the performance of CSF biomarkers for predicting risk of clinical decline and conversion to dementia in non-demented patients with cognitive symptoms. CSF samples from patients in two multicentre longitudinal studies (ADNI, n = 619; BioFINDER, n = 431) were analysed. Aß(1-42), tTau and pTau CSF concentrations were measured using Elecsys CSF immunoassays, and tTau/Aß(1-42) and pTau/Aß(1-42) ratios calculated. Patients were classified as biomarker (BM)-positive or BM-negative at baseline. Ability of biomarkers to predict risk of clinical decline and conversion to AD/dementia was assessed using pre-established cut-offs for Aß(1-42) and ratios; tTau and pTau cut-offs were determined. BM-positive patients showed greater clinical decline than BM-negative patients, demonstrated by greater decreases in MMSE scores (all biomarkers: -2.10 to -0.70). Risk of conversion to AD/dementia was higher in BM-positive patients (HR: 1.67 to 11.48). Performance of Tau/Aß(1-42) ratios was superior to single biomarkers, and consistent even when using cut-offs derived in a different cohort. Optimal pTau and tTau cut-offs were approximately 27 pg/mL and 300 pg/mL in both BioFINDER and ADNI. Elecsys pTau/Aß(1-42) and tTau/Aß(1-42) are robust biomarkers for predicting risk of clinical decline and conversion to dementia in non-demented patients, and may support AD diagnosis in clinical practice.

Cerebrospinal fluid and plasma biomarker trajectories with increasing amyloid deposition in Alzheimer's disease.

Failures in Alzheimer's disease (AD) drug trials highlight the need to further explore disease mechanisms and alterations of biomarkers during the development of AD. Using cross-sectional data from 377 participants in the BioFINDER study, we examined seven cerebrospinal fluid (CSF) and six plasma biomarkers in relation to ß-amyloid (Aß) PET uptake to understand their evolution during AD. In CSF, Aß42 changed first, closely followed by Aß42/Aß40, phosphorylated-tau (P-tau), and total-tau (T-tau). CSF neurogranin, YKL-40, and neurofilament light increased after the point of Aß PET positivity. The findings were replicated using Aß42, Aß40, P-tau, and T-tau assays from five different manufacturers. Changes were seen approximately simultaneously for CSF and plasma biomarkers. Overall, plasma biomarkers had smaller dynamic ranges, except for CSF and plasma P-tau which were similar. In conclusion, using state-of-the-art biomarkers, we identified the first changes in Aß, closely followed by soluble tau. Only after Aß PET became abnormal, biomarkers of neuroinflammation, synaptic dysfunction, and neurodegeneration were altered. These findings lend in vivo support of the amyloid cascade hypotheses in humans.

Multiplex proteomics identifies novel CSF and plasma biomarkers of early Alzheimer's disease.

To date, the development of disease-modifying therapies for Alzheimer's disease (AD) has largely focused on the removal of amyloid beta Aß fragments from the CNS. Proteomic profiling of patient fluids may help identify novel therapeutic targets and biomarkers associated with AD pathology. Here, we applied the Olink™ ProSeek immunoassay to measure 270 CSF and plasma proteins across 415 Aß- negative cognitively normal individuals (Aß- CN), 142 Aß-positive CN (Aß+ CN), 50 Aß- mild cognitive impairment (MCI) patients, 75 Aß+ MCI patients, and 161 Aß+ AD patients from the Swedish BioFINDER study. A validation cohort included 59 Aß- CN, 23 Aß- + CN, 44 Aß- MCI and 53 Aß+ MCI. To compare protein concentrations in patients versus controls, we applied multiple linear regressions adjusting for age, gender, medications, smoking and mean subject-level protein concentration, and corrected findings for false discovery rate (FDR, q < 0.05). We identified, and replicated, altered levels of ten CSF proteins in Aß+ individuals, including CHIT1, SMOC2, MMP-10, LDLR, CD200, EIF4EBP1, ALCAM, RGMB, tPA and STAMBP (- 0.14 < d < 1.16; q < 0.05). We also identified and replicated alterations of six plasma proteins in Aß+ individuals OSM, MMP-9, HAGH, CD200, AXIN1, and uPA (- 0.77 < d < 1.28; q < 0.05). Multiple analytes associated with cognitive performance and cortical thickness (q < 0.05). Plasma biomarkers could distinguish AD dementia (AUC = 0.94, 95% CI = 0.87-0.98) and prodromal AD (AUC = 0.78, 95% CI = 0.68-0.87) from CN. These findings reemphasize the contributions of immune markers, phospholipids, angiogenic proteins and other biomarkers downstream of, and potentially orthogonal to, Aß- and tau in AD, and identify candidate biomarkers for earlier detection of neurodegeneration.

ß-amyloid pathology and hippocampal atrophy are independently associated with memory function in cognitively healthy elderly.

The independent effects of different brain pathologies on age-dependent cognitive decline are unclear. We examined this in 300 cognitively unimpaired elderly individuals from the BioFINDER study. Using cognition as outcome we studied the effects of cerebrospinal fluid biomarkers for amyloid-ß (Aß42/40), neuroinflammation (YKL-40), and neurodegeneration and tau pathology (T-tau and P-tau) as well as MRI measures of white-matter lesions, hippocampal volume (HV), and regional cortical thickness. We found that Aß positivity and HV were independently associated with memory. Results differed depending on age, with memory being associated with HV (but not Aß) in older participants (73.3-88.4 years), and with Aß (but not HV) in relatively younger participants (65.2-73.2 years). This indicates that Aß and atrophy are independent contributors to memory variability in cognitively healthy elderly and that Aß mainly affects memory in younger elderly individuals. With advancing age, the effect of brain atrophy overshadows the effect of Aß on memory function.

Associations among amyloid status, age, and longitudinal regional brain atrophy in cognitively unimpaired older adults.

The goal of this study was to compare regional brain atrophy patterns in cognitively unimpaired (CU) older adults with and without brain accumulation of amyloid-ß (Aß) to elucidate contributions of Aß, age, and other variables to atrophy rates. In 80 CU participants from the Alzheimer's Disease Neuroimaging Initiative, we determined effects of Aß and age on longitudinal, regional atrophy rates, while accounting for confounding variables including sex, APOE ε4 genotype, white matter lesions, and cerebrospinal fluid total and phosphorylated tau levels. We not only found overlapping patterns of atrophy in Aß+ versus Aß- participants but also identified regions where atrophy pattern differed between the 2 groups. Higher Aß load was associated with increased longitudinal atrophy in the entorhinal cortex, amygdala, and hippocampus, even when accounting for age and other variables. Age was associated with atrophy in insula, fusiform gyrus, and isthmus cingulate, even when accounting for Aß. We found age by Aß interactions in the postcentral gyrus and lateral orbitofrontal cortex. These results elucidate the separate and related effects of age, Aß, and other important variables on longitudinal brain atrophy rates in CU older adults.

Staging ß-Amyloid Pathology With Amyloid Positron Emission Tomography.

IMPORTANCE: Different brain regions appear to be involved during ß-amyloid (Aß) accumulation in Alzheimer disease (AD), but a longitudinally valid system to track Aß stages in vivo using positron emission tomography (PET) is lacking. OBJECTIVE: To construct a longitudinally valid in vivo staging system for AD using amyloid PET. DESIGN, SETTING, AND PARTICIPANTS: Longitudinal multicenter cohort study using data accessed on August 20, 2018, from the Alzheimer's Disease Neuroimaging Initiative database of scans performed from June 9, 2010, to July 12, 2018, from 741 persons: 304 without cognitive impairment, 384 with mild cognitive impairment, and 53 with AD dementia. Cerebrospinal fluid (CSF) Aß42 and fluorine 18-labeled florbetapir (18F-florbetapir) data were used to determine early, intermediate, and late regions of Aß accumulation. ß-Amyloid stages ranging from 0 to 3 were constructed using these composites. Each subsequent stage required involvement of more advanced regions. Patients were followed up at 2, 4, and 6 years. Replication and validation were conducted using an independent cohort (Swedish BioFINDER) and gene expression information from the Allen Human Brain Atlas database. Analyses were conducted August 21, 2018, to May 24, 2019. MAIN OUTCOMES AND MEASURES: The main outcome was change in stage. Stages were compared for diagnosis, CSF biomarkers of tau, and longitudinal atrophy, cognitive measures, and regional gene expression. Transitions between stages were tested using longitudinal 18F-florbetapir data. RESULTS: Among 641 participants with CSF Aß42 data and at least two 18F-florbetapir scans, 335 (52.3%) were male. The early region of Aß accumulation included the precuneus, posterior cingulate, isthmus cingulate, insula, and medial and lateral orbitofrontal cortices. The late region included the lingual, pericalcarine, paracentral, precentral, and postcentral cortices. The intermediate region included remaining brain regions with increased accumulation rates. In 2072 PET scans from 741 participants, 2039 (98.4%) were unambiguously staged. At baseline, participants with stage 0 (n = 402) had a 14.7% (95% CI, 11.2%-18.1%) probability of progression to a higher stage; stage 1 (n = 21), 71.4% (95% CI, 50.0%-90.9%); and stage 2 (n = 79), 53.1% (95% CI, 42.2%-64.0%). Seven of the 741 participants (0.9%) reverted to a lower stage. Higher stages were associated with lower CSF Aß42 concentrations (from stage 1 at baseline), greater CSF P-tau (from stage 1) and CSF T-tau (from stage 2), and accelerated cognitive decline (from stage 2) and atrophy (from stage 3), even when adjusting for clinical diagnosis. Key findings were replicated in the BioFINDER cohort (N = 474). The regions of different stages differed by gene expression profiles when using the transcriptome from the Allen Human Brain Atlas, especially involving genes associated with voltage-gated ion channel activity especially involving genes associated with voltage-gated ion channel activity, but also blood circulation, axon guidance, and lipid transportation. CONCLUSIONS AND RELEVANCE: Results of this study suggest that this robust staging system of Aß accumulation may be useful for monitoring patients throughout the course of AD. Progression through stages may depend on underlying selective vulnerability in different brain regions.

Determining clinically meaningful decline in preclinical Alzheimer disease.

OBJECTIVE: To determine the time required for a preclinical Alzheimer disease population to decline in a meaningful way, use estimates of decline to update previous clinical trial design assumptions, and identify factors that modify ß-amyloid (Aß)-related decline. METHODS: In 1,120 cognitively unimpaired individuals from 3 international cohorts, we estimated the relationship between Aß status and longitudinal changes across multiple cognitive domains and assessed interactions between Aß and baseline factors. Power analyses were performed to explore sample size as a function of treatment effect. RESULTS: Cognitively unimpaired Aß+ participants approach mild cognitive impairment (MCI) levels of performance 6 years after baseline, on average. Achieving 80% power in a simulated 4-year treatment trial, assuming a 25% treatment effect, required 2,000 participants/group. Multiple factors interacted with Aß to predict cognitive decline; however, these findings were all cohort-specific. Despite design differences across the cohorts, with large sample sizes and sufficient follow-up time, the Aß+ groups declined consistently on cognitive composite measures. CONCLUSIONS: A preclinical AD population declines to the cognitive performance of an early MCI population in 6 years. Slowing this rate of decline by 40%-50% delays clinically relevant impairment by 3 years-a potentially meaningful treatment effect. However, assuming a 40%-50% drug effect highlights the difficulties in preclinical AD trial design, as a more commonly assumed treatment effect of 25% results in a required sample size of 2,000/group. Designers of preclinical AD treatment trials need to prepare for larger and longer trials than are currently being considered. Interactions with Aß status were inconsistent and not readily generalizable.

Diagnostic Value of Cerebrospinal Fluid Neurofilament Light Protein in Neurology: A Systematic Review and Meta-analysis.

IMPORTANCE: Neurofilament light protein (NfL) is elevated in cerebrospinal fluid (CSF) of a number of neurological conditions compared with healthy controls (HC) and is a candidate biomarker for neuroaxonal damage. The influence of age and sex is largely unknown, and levels across neurological disorders have not been compared systematically to date. OBJECTIVES: To assess the associations of age, sex, and diagnosis with NfL in CSF (cNfL) and to evaluate its potential in discriminating clinically similar conditions. DATA SOURCES: PubMed was searched for studies published between January 1, 2006, and January 1, 2016, reporting cNfL levels (using the search terms neurofilament light and cerebrospinal fluid) in neurological or psychiatric conditions and/or in HC. STUDY SELECTION: Studies reporting NfL levels measured in lumbar CSF using a commercially available immunoassay, as well as age and sex. DATA EXTRACTION AND SYNTHESIS: Individual-level data were requested from study authors. Generalized linear mixed-effects models were used to estimate the fixed effects of age, sex, and diagnosis on log-transformed NfL levels, with cohort of origin modeled as a random intercept. MAIN OUTCOME AND MEASURE: The cNfL levels adjusted for age and sex across diagnoses. RESULTS: Data were collected for 10 059 individuals (mean [SD] age, 59.7 [18.8] years; 54.1% female). Thirty-five diagnoses were identified, including inflammatory diseases of the central nervous system (n = 2795), dementias and predementia stages (n = 4284), parkinsonian disorders (n = 984), and HC (n = 1332). The cNfL was elevated compared with HC in a majority of neurological conditions studied. Highest levels were observed in cognitively impaired HIV-positive individuals (iHIV), amyotrophic lateral sclerosis, frontotemporal dementia (FTD), and Huntington disease. In 33.3% of diagnoses, including HC, multiple sclerosis, Alzheimer disease (AD), and Parkinson disease (PD), cNfL was higher in men than women. The cNfL increased with age in HC and a majority of neurological conditions, although the association was strongest in HC. The cNfL overlapped in most clinically similar diagnoses except for FTD and iHIV, which segregated from other dementias, and PD, which segregated from atypical parkinsonian syndromes. CONCLUSIONS AND RELEVANCE: These data support the use of cNfL as a biomarker of neuroaxonal damage and indicate that age-specific and sex-specific (and in some cases disease-specific) reference values may be needed. The cNfL has potential to assist the differentiation of FTD from AD and PD from atypical parkinsonian syndromes.

Performance of Fully Automated Plasma Assays as Screening Tests for Alzheimer Disease-Related ß-Amyloid Status.

IMPORTANCE: Accurate blood-based biomarkers for Alzheimer disease (AD) might improve the diagnostic accuracy in primary care, referrals to memory clinics, and screenings for AD trials. OBJECTIVE: To examine the accuracy of plasma ß-amyloid (Aß) and tau measured using fully automated assays together with other blood-based biomarkers to detect cerebral Aß. DESIGN, SETTING, AND PARTICIPANTS: Two prospective, cross-sectional, multicenter studies. Study participants were consecutively enrolled between July 6, 2009, and February 11, 2015 (cohort 1), and between January 29, 2000, and October 11, 2006 (cohort 2). Data were analyzed in 2018. The first cohort comprised 842 participants (513 cognitively unimpaired [CU], 265 with mild cognitive impairment [MCI], and 64 with AD dementia) from the Swedish BioFINDER study. The validation cohort comprised 237 participants (34 CU, 109 MCI, and 94 AD dementia) from a German biomarker study. MAIN OUTCOME AND MEASURES: The cerebrospinal fluid (CSF) Aß42/Aß40 ratio was used as the reference standard for brain Aß status. Plasma Aß42, Aß40 and tau were measured using Elecsys immunoassays (Roche Diagnostics) and examined as predictors of Aß status in logistic regression models in cohort 1 and replicated in cohort 2. Plasma neurofilament light chain (NFL) and heavy chain (NFH) and APOE genotype were also examined in cohort 1. RESULTS: The mean (SD) age of the 842 participants in cohort 1 was 72 (5.6) years, with a range of 59 to 88 years, and 446 (52.5%) were female. For the 237 in cohort 2, mean (SD) age was 66 (10) years with a range of 23 to 85 years, and 120 (50.6%) were female. In cohort 1, plasma Aß42 and Aß40 predicted Aß status with an area under the receiver operating characteristic curve (AUC) of 0.80 (95% CI, 0.77-0.83). When adding APOE, the AUC increased significantly to 0.85 (95% CI, 0.82-0.88). Slight improvements were seen when adding plasma tau (AUC, 0.86; 95% CI, 0.83-0.88) or tau and NFL (AUC, 0.87; 95% CI, 0.84-0.89) to Aß42, Aß40 and APOE. The results were similar in CU and cognitively impaired participants, and in younger and older participants. Applying the plasma Aß42 and Aß40 model from cohort 1 in cohort 2 resulted in slightly higher AUC (0.86; 95% CI, 0.81-0.91), but plasma tau did not contribute. Using plasma Aß42, Aß40, and APOE in an AD trial screening scenario reduced positron emission tomography costs up to 30% to 50% depending on cutoff. CONCLUSIONS AND RELEVANCE: Plasma Aß42 and Aß40 measured using Elecsys immunoassays predict Aß status in all stages of AD with similar accuracy in a validation cohort. Their accuracy can be further increased by analyzing APOE genotype. Potential future applications of these blood tests include prescreening of Aß positivity in clinical AD trials to lower the costs and number of positron emission tomography scans or lumbar punctures.

Association Between Longitudinal Plasma Neurofilament Light and Neurodegeneration in Patients With Alzheimer Disease.

Importance: Plasma neurofilament light (NfL) has been suggested as a noninvasive biomarker to monitor neurodegeneration in Alzheimer disease (AD), but studies are lacking. Objective: To examine whether longitudinal plasma NfL levels are associated with other hallmarks of AD. Design, Setting, and Participants: This North American cohort study used data from 1583 individuals in the multicenter Alzheimer's Disease Neuroimaging Initiative study from September 7, 2005, through June 16, 2016. Patients were eligible for inclusion if they had NfL measurements. Annual plasma NfL samples were collected for up to 11 years and were analyzed in 2018. Exposures: Clinical diagnosis, Aß and tau cerebrospinal fluid (CSF) biomarkers, imaging measures (magnetic resonance imaging and fluorodeoxyglucose-positron emission tomography), and tests on cognitive scores. Main Outcomes and Measures: The primary outcome was the association between baseline exposures (diagnosis, CSF biomarkers, imaging measures, and cognition) and longitudinal plasma NfL levels, analyzed by an ultrasensitive assay. The secondary outcomes were the associations between a multimodal classification scheme with Aß, tau, and neurodegeneration (ie, the ATN system) and plasma NfL levels and between longitudinal changes in plasma NfL levels and changes in the other measures. Results: Of the included 1583 participants, 716 (45.2%) were women, and the mean (SD) age was 72.9 (7.1) years; 401 had no cognitive impairment, 855 had mild cognitive impairment, and 327 had AD dementia. The NfL level was increased at baseline in patients with mild cognitive impairment and AD dementia (mean levels: cognitive unimpairment, 32.1 ng/L; mild cognitive impairment, 37.9 ng/L; and AD dementia, 45.9 ng/L; P < .001) and increased in all diagnostic groups, with the greatest increase in patients with AD dementia. A longitudinal increase in NfL level correlated with baseline CSF biomarkers (low Aß42 [P = .001], high total tau [P = .02], and high phosphorylated tau levels [P = .02]), magnetic resonance imaging measures (small hippocampal volumes [P < .001], thin regional cortices [P = .009], and large ventricular volumes [P = .002]), low fluorodeoxyglucose-positron emission tomography uptake (P = .01), and poor cognitive performance (P < .001) for a global cognitive score. With use of the ATN system, increased baseline NfL levels were seen in A-T+N+ (P < .001), A+T-N+ (P < .001), and A+T+N+ (P < .001), and increased rates of NfL levels were seen in A-T+N- (P = .009), A-T+N+ (P = .02), A+T-N+ (P = .04), and A+T+N+ (P = .002). Faster increase in NfL levels correlated with faster increase in CSF biomarkers of neuronal injury, faster rates of atrophy and hypometabolism, and faster worsening in global cognition (all P < .05 in patients with mild cognitive impairment; associations differed slightly in cognitively unimpaired controls and patients with AD dementia). Conclusions and Relevance: The findings suggest that plasma NfL can be used as a noninvasive biomarker associated with neurodegeneration in patients with AD and may be useful to monitor effects in trials of disease-modifying drugs.

Serum tau fragments as predictors of death or poor neurological outcome after out-of-hospital cardiac arrest.

Background: Anoxic brain injury is the primary cause of death after resuscitation from out-of-hospital cardiac arrest (OHCA) and prognostication is challenging. The aim of this study was to evaluate the potential of two fragments of tau as serum biomarkers for neurological outcome. Methods: Single-center sub-study of 171 patients included in the Target Temperature Management (TTM) Trial randomly assigned to TTM at 33 °C or TTM at 36 °C for 24 h after OHCA. Fragments (tau-A and tau-C) of the neuronal protein tau were measured in serum 24, 48 and 72 h after OHCA. The primary endpoint was neurological outcome. Results: Median (quartile 1 - quartile 3) tau-A (ng/ml) values were 58 (43-71) versus 51 (43-67), 72 (57-84) versus 71 (59-82) and 76 (61-92) versus 75 (64-89) for good versus unfavourable outcome at 24, 48 and 72 h, respectively (pgroup = 0.95). Median tau C (ng/ml) values were 38 (29-50) versus 36 (29-49), 49 (38-58) versus 48 (33-59) and 48 (39-59) versus 48 (36-62) (pgroup = 0.95). Tau-A and tau-C did not predict neurological outcome (area under the receiver-operating curve at 48 h; tau-A: 0.51 and tau-C: 0.51). Conclusions: Serum levels of tau fragments were unable to predict neurological outcome after OHCA.