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Background: Among the Alzheimer's disease (AD) biomarkers measured in blood, phosphorylated forms of tau (p-tau) have been shown to exhibit a particularly high diagnostic potential. Here, we performed a comprehensive method comparison study, followed by evaluation of the diagnostic performance of eight recent plasma p-tau immunoassays targeting different tau phosphorylation sites, different tau fragments, and that are measured by two distinct platforms. Methods: We enrolled a cohort of 40 patients with AD at the stage of dementia (AD-dem) characterized by positive CSF A + T + profile, and a control group of 40 cognitively healthy participants (Control), to conduct a comprehensive method comparison for three plasma p-tau181 and five plasma p-tau217 assays run on the Simoa® HD-X™ or Lumipulse® G600II/G1200 platforms. Design of the compared assays differed in regard to: (1) tau phosphorylation site targeted by the capture antibody (T181 or T217), and (2) epitope of the pan-tau detector antibody (N-terminal or mid-region). For each of the assays we determined precision and analytical sensitivity parameters and used Passing-Bablok regression and Bland-Altman plots for pairwise comparison of p-tau181 or p-tau217 assays. Subsequently, we evaluated the diagnostic accuracy of all the assays for discrimination between AD-dem and Control groups. Results: We found a strong, positive correlation between all the measurements. Fixed and/or proportional bias was observed for each of compared p-tau181 assay pairs or p-tau217 assay pairs. While both plasma p-tau181 and p-tau217 levels were significantly increased in AD-dem vs. Control groups as measured by all assays, higher median concentration AD-dem/Control fold change and AUC values were observed for p-tau217 (assays range: fold change 3.72–6.74, AUC 0.916–0.956) compared with p-tau181 (assays range 1.81–2.94, AUC 0.829–0.909), independently of the platform used. No significant differences were observed between diagnostic performance of p-tau181 assays or p-tau217 assays targeting tau N-terminus or mid-region. Conclusions: Although all plasma p-tau measurements enabled discrimination between clinical groups, p-tau217 assays showed the highest robustness, independently of the pan-tau detector antibody targeting N-terminal or mid-region, and independently of the platform used. Considering the observed method disagreement in measured absolute concentrations, we stress the need for development of certified reference material, harmonizing measurements across different platforms. [ABSTRACT FROM AUTHOR]

Spinal muscular atrophy (SMA) is the leading genetic cause of infant mortality, characterized by progressive neuromuscular degeneration resulting from mutations in the survival motor neuron (SMN1) gene. The availability of disease-modifying therapies for SMA therapies highlights the pressing need for easily accessible and cost-effective blood biomarkers to monitor treatment response and for better disease management. Additionally, the wide implementation of newborn genetic screening programs in Western countries enables presymptomatic diagnosis of SMA and immediate treatment administration. However, the absence of monitoring and prognostic blood biomarkers for neurodegeneration in SMA hinders effective disease management. Neurofilament light protein (NfL) is a promising biomarker of neuroaxonal damage in SMA and reflects disease progression in children with SMA undergoing treatment. Recently, the European Medicines Agency issued a letter of support endorsing the potential utilization of NfL as a biomarker of pediatric neurological diseases, including SMA. Within this review, we comprehensively assess the potential applications of NfL as a monitoring biomarker for disease severity and treatment response in pediatric-onset SMA. We provide reference ranges for normal levels of serum based NfL in neurologically healthy children aged 0–18 years. These reference ranges enable accurate interpretation of NfL levels in children and can accelerate the implementation of NfL into clinical practice. [ABSTRACT FROM AUTHOR]

Background: Several assays reliably measure cerebrospinal fluid (CSF) total tau (t‐tau) protein for Alzheimer's diseases (AD) diagnosis. However, CSF sampling is invasive and hampers availability of biomarker testing in AD. Therefore, less invasive blood t‐tau assays are needed, preferably on different platforms to enable implementation in different clinical settings. Point‐of‐care (POC) platforms enable the development of practical and easily implemented assays. Here, we aim to develop and compare two blood t‐tau POC‐assays, (1)on the Ella microfluidics platform and (2)using upconversion‐nanoparticle based lateral flow (UCNP‐LF), for use in AD diagnosis. Method: The prototype assays were developed with the same pair of antibodies (capture‐mAb: ADx205 and detector‐mAb: ADx204 having epitopes in respectively the regions aa 194‐204 and 1‐20) and were calibrated using a recombinant protein (2N4R tau). For the Ella‐assay, we validated the analytical sensitivity, precision (4 different runs) and parallelism. The acceptance range was set to <15% coefficient of variation (CV) for precision and 85‐115% of slope‐accuracy for parallelism. Detectability of t‐tau was assessed using 20 plasma samples, including 10 AD‐dementia patients (age: 64±9y, 60%F) and 10 controls (age: 67±8y, 50%F). For the UCNP‐LF assay, spiked buffer and serum were used for preliminary performance testing. Result: For the Ella assay, we determined a limit of detection (LoD) of 3 pg/mL based on mean signal of 16 blanks plus 10x SD (figure1). The assay quantified t‐tau in the clinical samples above assay blank with an average intra‐assay CV of 5.3%. Average intra‐ and inter‐assay CV for QC plasma samples were 8% and 11.4%. The assay showed robust mean parallelism response of (95%) (figure 2). Median t‐tau concentration in AD samples was 36.9 pg/mL vs 8 pg/mL in controls. The prototype UCNP‐LF assay showed a LoD of 92 pg/mL, based upon spiked buffer with the recombinant protein, and 102 pg/mL for spiked serum (figure3). The UCNP‐LF assay has a read‐out time of 30 minutes. Conclusion: The prototype assays showed promising preliminary performance. Next, a technology comparison using Bland‐Altman graphs on samples of at least two different clinical groups, would be measured using a reference immunoassay platform, such as Simoa. [ABSTRACT FROM AUTHOR]

Proteomics studies have shown differential expression of numerous proteins in dementias but have rarely led to novel biomarker tests for clinical use. The Marie Curie MIRIADE project is designed to experimentally evaluate development strategies to accelerate the validation and ultimate implementation of novel biomarkers in clinical practice, using proteomics-based biomarker development for main dementias as experimental case studies. We address several knowledge gaps that have been identified in the field. First, there is the technology-translation gap of different technologies for the discovery (e.g., mass spectrometry) and the large-scale validation (e.g., immunoassays) of biomarkers. In addition, there is a limited understanding of conformational states of biomarker proteins in different matrices, which affect the selection of reagents for assay development. In this review, we aim to understand the decisions taken in the initial steps of biomarker development, which is done via an interim narrative update of the work of each ESR subproject. The results describe the decision process to shortlist biomarkers from a proteomics to develop immunoassays or mass spectrometry assays for Alzheimer's disease, Lewy body dementia, and frontotemporal dementia. In addition, we explain the approach to prepare the market implementation of novel biomarkers and assays. Moreover, we describe the development of computational protein state and interaction prediction models to support biomarker development, such as the prediction of epitopes. Lastly, we reflect upon activities involved in the biomarker development process to deduce a best-practice roadmap for biomarker development., Competing Interests: SD is an employee of ADx NeuroSciences, Gent, Belgium. SC is an employee of National Measurement Laboratory at LGC, London, UK. CT has a collaboration contract with ADx Neurosciences, Quanterix, and Eli Lilly, performed contract research or received grants from AC-Immune, Axon Neurosciences, Bioconnect, Biogen, Brainstorm Therapeutics, Celgene, EIP Pharma, Eisai, PeopleBio, Quanterix, Roche, Toyama, and Vivoryon. She serves on editorial boards of Medidact Neurologie/Springer, Alzheimer Research and Therapy, Neurology: Neuroimmunology & Neuroinflammation, and is editor of a Neuromethods book Springer. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Mavrina, Kimble, Waury, Gogishvili, Gómez de San José, Das, Coppens, Fernandes Gomes, Mravinacová, Wojdała, Bolsewig, Bayoumy, Burtscher, Mohaupt, Willemse, Teunissen and the MIRIADE consortium.)