BackgroundThe last few years have seen major advances in blood biomarkers for Alzheimer's Disease (AD) with the development of ultrasensitive immunoassays, promising to transform how we diagnose, prognose, and track progression of neurodegenerative dementias.MethodsWe evaluated a panel of four novel ultrasensitive electrochemiluminescence (ECL) immunoassays against presumed CNS derived proteins of interest in AD in plasma [phosphorylated-Tau181 (pTau181), total Tau (tTau), neurofilament light (NfL), and glial fibrillary acidic protein (GFAP)]. Two sets of banked plasma samples from the Massachusetts Alzheimer's Disease Research Center's longitudinal cohort study were examined: A longitudinal prognostic sample (n = 85) consisting of individuals with mild cognitive impairment (MCI) and 4 years of follow-up and a cross-sectional sample (n = 238) consisting of individuals with AD, other neurodegenerative diseases (OND), and normal cognition (CN).ResultsParticipants with MCI who progressed to dementia due to probable AD during follow-up had higher baseline plasma concentrations of pTau181, NfL, and GFAP compared to non-progressors. The best prognostic discrimination was observed with pTau181 (AUC = 0.83, 1.7-fold increase) and GFAP (AUC = 0.83, 1.6-fold increase). Participants with autopsy- and/or biomarker verified AD had higher plasma levels of pTau181, tTau and GFAP compared to CN and OND, while NfL was elevated in AD and further increased in OND. The best diagnostic discrimination was observed with pTau181 (AD vs CN: AUC = 0.90, 2-fold increase; AD vs. OND: AUC = 0.84, 1.5-fold increase) but tTau, NfL, and GFAP also showed good discrimination between AD and CN (AUC = 0.81–0.85; 1.5–2.2 fold increase).ConclusionsThese new ultrasensitive ECL plasma assays for pTau181, tTau, NfL, and GFAP demonstrated diagnostic utility for detection of AD. Moreover, the absolute baseline plasma levels of pTau181 and GFAP reflect cognitive decline over the next 4 years, providing prognostic information that may have utility in both clinical practice and clinical trial populations.

Background: The last few years have seen major advances in blood biomarkers for Alzheimer's Disease (AD) with the development of ultrasensitive immunoassays, promising to transform how we diagnose, prognose, and track progression of neurodegenerative dementias. Methods: We evaluated a panel of four novel ultrasensitive electrochemiluminescence (ECL) immunoassays against presumed CNS derived proteins of interest in AD in plasma [phosphorylated-Tau181 (pTau181), total Tau (tTau), neurofilament light (NfL), and glial fibrillary acidic protein (GFAP)]. 366 plasma samples from the Massachusetts Alzheimer's Disease Research Center's longitudinal cohort study were examined to differentiate definite AD, other neurodegenerative diseases (OND), and cognitively normal (CN) individuals. A subset of samples were selected to have longitudinal follow up to also determine the utility of this plasma biomarker panel in predicting 4-year risk for cognitive decline in individuals with different levels of cognitive impairment. Results: pTau181, tTau and GFAP were higher in AD compared to CN and OND, while NfL was elevated in AD and further increased in OND. pTau181 performed the best (AD vs CN: AUC=0.88, 2-fold increase; AD vs OND: AUC=0.78, 1.5-fold increase) but tTau also showed excellent discrimination (AD vs CN: AUC=0.79, 1.5-fold increase; AD vs OND: AUC=0.72, 1.3-fold increase). Participants with MCI who progressed to AD dementia had higher baseline plasma concentrations of pTau181, NfL, and GFAP compared to non-progressors with the best discrimination for pTau181 (AUC=0.82, 1.7-fold increase) and GFAP (AUC=0.81, 1.6-fold increase). Conclusions: These new ultrasensitive ECL plasma assays for pTau181, tTau, NfL, and GFAP detect CNS disease with high specificity and accuracy. Moreover, the absolute baseline plasma levels of pTau and GFAP reflect clinical disease aggressiveness over the next 4 years, providing diagnostic and prognostic information that may have utility in both clinical and clinical trial populations. Classification of Evidence: This study provides Class II evidence that plasma levels of pTau181, tTau, NfL, and GFAP are associated with AD and that pTau181 and GFAP are associated with progression from MCI to AD dementia.

BackgroundNormal Pressure Hydrocephalus (NPH) is a neurological condition where there is enlarged ventricular size with normal opening pressure at lumbar puncture. Etiology is uncertain but it is presumed to occur from an imbalance in the production and/or absorption of cerebrospinal fluid (CSF) leading to expansion of the ventricles. Clinical features include gait dysfunction, cognitive impairments, bladder incontinence. Diagnosis is challenging, given a large overlap in clinical and neuroradiological features and co‐morbidity with other more common diseases of aging, especially Alzheimer’s disease (AD) and Lewy body diseases. CSF amyloid and tau biomarkers can be helpful to identify AD pathology but do not exclude concurrent NPH. Currently, there are no biofluid biomarkers to assist in diagnosis of NPH. Here we describe a proteomic discovery pilot to identify candidate protein biomarkers associated with NPH.Method176 banked CSF samples from the MassGeneral Institute for Neurodegenerative Disease biorepository were separated into three groups: NPH (n=30), AD (n=65), and cognitively unimpaired neurological controls (CU‐N; n=81). Diagnoses were established based on comprehensive chart review and CSF AD biomarkers. For proteomic analysis, samples were prepared in batches and analyzed by LC‐MS/MS on an Orbitrap Fusion using a data‐independent acquisition method with non‐overlapping windows from 400‐1000 m/z. Batches were run sequentially, and raw files were searched per batch using Scaffold‐DIA and a custom data‐dependent generated library.ResultFive proteins present in hemoglobulin (HBD and HBB), immunoglobulins (LV39 and KV105), and fibrinogen (FIBA) were increased in NPH compared to AD (Benjamini‐Hochberg adjusted p‐value pAdj <0.05). CSF erythrocyte counts were undetectable in all but one NPH subjects suggesting that a traumatic LP was not the cause of the increased levels. Two neuron associated proteins (VGF and NPTXR) were detected at lower levels in NPH compared to CU‐N subjects (pAdj<0.0001). Alpha‐1‐antichymotrypsin (AACT), was detected at high concentrations both in NPH and AD compared to CU‐N subjects (pAdj<0.02).ConclusionProteomic analysis in NPH may identify novel pathological processes involved in the disease process and aid in the development of biomarkers in NPH.