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The Alzheimer's disease (AD) process is likely initiated many years before clinical onset. Biomarkers of preclinical disease are critical for the development of disease-modifying or even preventative therapies. Current biomarkers for early disease, including cerebrospinal fluid tau and amyloid β (Aβ) levels, structural and functional magnetic resonance imaging, and the use of brain amyloid imaging, are limited because they are very invasive or expensive. Noninvasive biomarkers may be a more accessible alternative, but none can currently detect preclinical AD with the required sensitivity and specificity. Here, we show a novel, straight-forward, and noninvasive approach for assessment of early stages of cognitive decline. Salivary samples from cases of amnestic mild cognitive impairment (aMCI) and AD, and neurology controls were analyzed. We have discovered and validated a new single saliva biomarker, lactoferrin, which in our cross-sectional investigation perfectly discriminates clinically diagnosed aMCI and AD patients from a cognitively healthy control group. The accuracy for AD diagnosis shown by salivary lactoferrin was greater than that obtained from core cerebrospinal fluid (CSF) biomarkers, including total tau and CSF Aβ42. Furthermore, salivary lactoferrin can be used for population screening and for identifying those underdiagnosed subjects with very early stages of mild cognitive impairment and AD. This biomarker may offer new insights in the early diagnostics for AD. The authors are grateful to Juan Carlos del Castillo who participated in the promotion of this study. The authors specially thank Raquel Cobos, Consuelo Pascual, Desiree Antequera, Jose Javier Aguirre, Belén González-Lahera, Alicia Maroto, and Ana B. Pastor for their helpful support and technical assistance. The authors want to particularly acknowledge the patients enrolled in this study for their participation and the Biobanco imas12 in Hospital 12 de Octubre integrated in the in Spanish Hospital Biobanks Network (RetBioH; www.redbiobancos.es). Biobank is supported by Instituto de Salud Carlos III. This work was supported by a grant from GEROA Diagnostics (grant 2015/82). Sí

Background The Neurological Disorders in Central Spain, second survey (NEDICES-2) is a population-based, closed-cohort study that will include over 8000 subjects aged ≥55 years. It will also include a biobank. Objective The objective of this study was to evaluate all major aspects of the NEDICES-2 (methods, database, screening instruments, and questionnaires, as well as interexpert rating of the neurological diagnoses) in each one of the planned areas (all of them in central Spain) and to test the possibility of obtaining biological samples from each participant. Methods A selection of patients and participants of the planned NEDICES-2 underwent face-to-face interviews including a comprehensive questionnaire on demographics, current medications, medical conditions, and lifestyle habits. Biological samples (blood, saliva, urine, and hair) were also obtained. Furthermore, every participant was examined by a neurologist. Results In this pilot study, 567 study participants were enrolled (196 from hospitals and 371 from primary care physician lists). Of these 567, 310 completed all study procedures (questionnaires and the neurological evaluation). The study was time-consuming for several primary care physicians. Hence, a few primary care physicians from some areas refused to participate, which led to a reconfiguration of study areas. In addition, the central biobank needed to be supplemented by the biobanks of local Spanish National Health System hospitals. Conclusions Population-based epidemiological surveys, such as the NEDICES-2, require a pilot study to evaluate the feasibility of all aspects of a future field study (population selection, methods and instruments to be used, neurological diagnosis agreement, and data collection)., Our thanks to all collaborators in this feasibility pilot study, the Instituto de Salud Carlos III and the Biomedical Research Networking Center on Neurodegenerative Diseases (CIBERNED), and the two hospital computer experts (Victoria Garcia Baquero and Teresa Garcia Morales), who created the website (http://nedices2.ciberned.com/estudio-de-salud-nedices-2/). We would also like to thank Miss Jennifer Gates for the editing and proofreading of the manuscript.