Early diagnosis of neurodegenerative disorders such as Alzheimer's (AD) or Parkinson's disease (PD) is needed to slow down or halt the disease at the earliest stage. Cerebrospinal fluid (CSF) biomarkers can be a good tool for early diagnosis. However, their use in clinical practice is challenging due to the high variability found between centers in the concentrations of both AD CSF biomarkers (Aβ42, total tau and phosphorylated tau) and PD CSF biomarker (α-synuclein). Such a variability has been partially attributed to different preanalytical procedures between laboratories, thus highlighting the need to establish standardized operating procedures. Here, we merge two previous consensus guidelines for preanalytical confounding factors in order to achieve one exhaustive guideline updated with new evidence for Aβ42, total tau and phosphorylated tau, and α-synuclein. The proposed standardized operating procedures are applicable not only to novel CSF biomarkers in AD and PD, but also to biomarkers for other neurodegenerative disorders.

Abstract. Diagnostic processes of Alzheimer's disease (AD) are evolving. Knowledge about disease-specific biomarkers is constantly increasing and larger volumes of data are being measured from patients. To gain additional benefits from the collected data, a novel statistical modeling and data visualization system is proposed for supporting clinical diagnosis of AD. The proposed system computes an evidence-based estimate of a patient's AD state by comparing his or her heterogeneous neuropsychological, clinical, and biomarker data to previously diagnosed cases. The AD state in this context denotes a patient's degree of similarity to a previously diagnosed disease population. A summary of patient data and results of the computation are displayed in a succinct Disease State Fingerprint (DSF) visualization. The visualization clearly discloses how patient data contributes to the AD state, facilitating rapid interpretation of the information. To model the AD state from complex and heterogeneous patient data, a statistical Disease State Index (DSI) method underlying the DSF has been developed. Using baseline data from the Alzheimer's Disease Neuroimaging Initiative (ADNI), the ability of the DSI to model disease progression from elderly healthy controls to AD and its ability to predict conversion from mild cognitive impairment (MCI) to AD were assessed. It was found that the DSI provides well-behaving AD state estimates, corresponding well with the actual diagnoses. For predicting conversion from MCI to AD, the DSI attains performance similar to state-of-the-art reference classifiers. The results suggest that the DSF establishes an effective decision support and data visualization framework for improving AD diagnostics, allowing clinicians to rapidly analyze large quantities of diverse patient data.

To use proteomic analysis of cerebrospinal fluid to discover novel proteins and peptides able to differentiate between patients with stable mild cognitive impairment (MCI) and those who will progress to Alzheimer disease (AD). Design: Baseline cerebrospinal fluid samples from patients with MCI and healthy controls were profiled using surface-enhanced laser desorption/ionization time-offlight mass spectrometry. Setting: Memory disorder clinic. Participants: Patients with MCI (n = 113), of whom 56 were cognitively stable and 57 progressed to AD with dementia during a 4-to 6-year follow-up, as well as 28 healthy controls who were followed up for 3 years. Main Outcome Measure: During follow-up, 57 patients progressed to AD and 56 patients had stable MCI. Cerebrospinal fluid from these 2 groups of patients was compared using surface-enhanced laser desorption/ ionization time-of-flight mass spectrometry. Results: We identified a panel of 17 potential biomarkers that could distinguish between patients with stable MCI and patients with MCI who progressed to AD. We have positively identified and characterized 5 of the potential biomarkers. Conclusions: Proteomic profiling of cerebrospinal fluid provided a novel panel of 17 potential biomarkers for prediction of MCI progression to AD. The 5 identified biomarkers are relevant to the pathogenesis of AD and could help gain an understanding of the molecular pathways in which they may function.

Scope: The aim of this study was to develop and evaluate a parallel reaction monitoring mass spectrometry (PRM-MS) assay consisting of a panel of potential protein biomarkers in cerebrospinal fluid (CSF). Experimental design: Thirteen proteins were selected based on their association with neurodegenerative diseases and involvement in synaptic function, secretory vesicle function, or innate immune system. CSF samples were digested and two to three peptides per protein were quantified using stable isotope-labeled peptide standards. Results: Coefficients of variation were generally below 15%. Clinical evaluation was performed on a cohort of 10 patients with Alzheimer's disease (AD) and 15 healthy subjects. Investigated proteins of the granin family exhibited the largest difference between the patient groups. Secretogranin-2 (p<0.005) and neurosecretory protein VGF (p<0.001) concentrations were lowered in AD. For chromogranin A, two of three peptides had significantly lowered AD concentrations (p<0.01). The concentrations of the synaptic proteins neurexin-1 and neuronal pentraxin-1, as well as neurofascin were also significantly lowered in AD (p<0.05). The other investigated proteins, β2-microglobulin, cystatin C, amyloid precursor protein, lysozyme C, neurexin-2, neurexin-3, and neurocan core protein, were not significantly altered. Conclusion and clinical relevance: PRM-MS of protein panels is a valuable tool to evaluate biomarker candidates for neurodegenerative disorders.

This article presents recommendations, based on the Grading of Recommendations, Assessment, Development, and Evaluation method, for the clinical application of cerebrospinal fluid (CSF) amyloid-β, tau, and phosphorylated tau in the diagnostic evaluation of patients with mild cognitive impairment (MCI). The recommendations were developed by a multidisciplinary working group and based on the available evidence and consensus from focused group discussions for 1) prediction of clinical progression to Alzheimer's disease (AD) dementia, 2) cost-effectiveness, 3) interpretation of results, and 4) patient counseling. The working group recommended using CSF AD biomarkers in the diagnostic workup of MCI patients, after prebiomarker counseling, as an add-on to clinical evaluation to predict functional decline or conversion to AD dementia and to guide disease management. Because of insufficient evidence, it was uncertain whether CSF AD biomarkers outperform imaging biomarkers. Furthermore, the working group provided recommendations for interpretation of ambiguous CSF biomarker results and for pre- and post-biomarker counseling.

This article presents recommendations, based on the Grading of Recommendations, Assessment, Development, and Evaluation method, for the clinical application of cerebrospinal fluid (CSF) amyloid-β, tau, and phosphorylated tau in the diagnostic evaluation of patients with dementia. The recommendations were developed by a multidisciplinary working group based on the available evidence and consensus from focused discussions for (i) identification of Alzheimer's disease (AD) as the cause of dementia, (ii) prediction of rate of decline, (iii) cost-effectiveness, and (iv) interpretation of results. The working group found sufficient evidence to support a recommendation to use CSF AD biomarkers as a supplement to clinical evaluation, particularly in uncertain and atypical cases, to identify or exclude AD as the cause of dementia. Because of insufficient evidence, it was uncertain whether CSF AD biomarkers outperform imaging biomarkers. Operational recommendations for the interpretation of ambiguous CSF biomarker results were also provided.

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Conflict of interest statement AL has served at scientific advisory boards of Fujirebio Europe, Eli Lilly, Novartis and Nutricia and is the inventor of a patent on synaptic markers in CSF. LP has received honoraria as member of advisory boards from Fujirebio Europe, IBL International, Merck, Roche and Biogen.