title: The Dutch Parelsnoer Institute--Neurodegenerative diseases; methods, design and baseline results.
abstract: BACKGROUND
  The Parelsnoer Institute is a collaboration between 8 Dutch University Medical Centers in which clinical data and biomaterials from patients suffering from chronic diseases (so called "Pearls") are collected according to harmonized protocols. The Pearl Neurodegenerative Diseases focuses on the role of biomarkers in the early diagnosis, differential diagnosis and in monitoring the course of neurodegenerative diseases, in particular Alzheimer's disease. The objective of this paper is to describe the design and methods of the Pearl Neurodegenerative Diseases, as well as baseline descriptive variables, including their biomarker profile.
  
  
  METHODS
  The Pearl Neurodegenerative Diseases is a 3-year follow-up study of patients referred to a memory clinic with cognitive complaints. At baseline, all patients are subjected to a standardized examination, including clinical data and biobank materials, e.g. blood samples, MRI and cerebrospinal fluid. At present, in total more than 1000 patients have been included, of which cerebrospinal fluid and DNA samples are available of 211 and 661 patients, respectively. First descriptives of a subsample of the data (n = 665) shows that patients are diagnosed with dementia (45%), mild cognitive impairment (31%), and subjective memory complaints (24%).
  
  
  CONCLUSIONS
  The Pearl Neurodegenerative Diseases is an ongoing large network collecting clinical data and biomaterials of more than 1000 patients with cognitive impairments. The project has started with data analyses of the baseline characteristics and biomarkers, which will be the starting point of future specific research questions that can be answered by this unique dataset.
authors.affiliation: Alzheimer Center Limburg, School for Mental Health and Neuroscience (MHeNS), Maastricht University Medical Center, P.O. Box 616, 6200 MD, Maastricht, The Netherlands. p.aalten@maastrichtuniversity.nl.
authors.forename: Pauline
authors.initials: P
authors.lastname: Aalten
authors.affiliation: Alzheimer Center Limburg, School for Mental Health and Neuroscience (MHeNS), Maastricht University Medical Center, P.O. Box 616, 6200 MD, Maastricht, The Netherlands. i.ramakers@maastrichtuniversity.nl.
authors.forename: Inez H G B
authors.initials: IH
authors.lastname: Ramakers
authors.affiliation: Departments of Neurology and Geriatrics, University Medical Center Utrecht, Utrecht, The Netherlands. g.j.biessels@umcutrecht.nl.
authors.forename: Geert Jan
authors.initials: GJ
authors.lastname: Biessels
authors.affiliation: Department of Neurology, Alzheimer Research Cente, University Medical Center Groningen, Utrecht, The Netherlands. p.p.de.deyn@umcg.nl.
authors.forename: Peter Paul
authors.initials: PP
authors.lastname: de Deyn
authors.affiliation: Departments of Neurology and Geriatrics, University Medical Center Utrecht, Utrecht, The Netherlands. h.l.koek@umcutrecht.nl.
authors.forename: Huiberdina L
authors.initials: HL
authors.lastname: Koek
authors.affiliation: Alzheimer Center Nijmegen, Radboud University Medical Center Nijmegen, Nijmegen, The Netherlands. m.olde-rikkert@ger.umcn.nl.
authors.forename: Marcel G M
authors.initials: MG
authors.lastname: OldeRikkert
authors.affiliation: Department of Gerontology and Geriatrics, Leiden University Medical Center, Leiden, The Netherlands. a.m.oleksik@lumc.nl.
authors.forename: Ania M
authors.initials: AM
authors.lastname: Oleksik
authors.affiliation: Department of Neurology, Academic Medical Center Amsterdam, Amsterdam, The Netherlands. e.richard@amc.uva.nl.
authors.forename: Edo
authors.initials: E
authors.lastname: Richard
authors.affiliation: Alzheimer Center Amsterdam, VU Medical Center Amsterdam, Amsterdam, The Netherlands. l.smits@vumc.nl.
authors.forename: Lieke L
authors.initials: LL
authors.lastname: Smits
authors.affiliation: Departments of Neurology and Radiology, Erasmus Medical Center, Rotterdam, The Netherlands. j.c.vanswieten@erasmusmc.nl.
authors.forename: John C
authors.initials: JC
authors.lastname: van Swieten
authors.affiliation: Department of Neurology, Alzheimer Research Cente, University Medical Center Groningen, Utrecht, The Netherlands. l.k.teune@umcg.nl.
authors.forename: Laura K
authors.initials: LK
authors.lastname: Teune
authors.affiliation: Departments of Neurology and Radiology, Erasmus Medical Center, Rotterdam, The Netherlands. a.vanderlugt@erasmusmc.nl.
authors.forename: Aad
authors.initials: A
authors.lastname: van der Lugt
authors.affiliation: Alzheimer Center Amsterdam, VU Medical Center Amsterdam, Amsterdam, The Netherlands. f.barkhof@vumc.nl.
authors.forename: Frederik
authors.initials: F
authors.lastname: Barkhof
authors.affiliation: Department of Clinical Chemistry, Neurochemistry Laboratory and Biobank, VU Medical Center Amsterdam, Amsterdam, The Netherlands. c.teunissen@vumc.nl.
authors.forename: Charlotte E
authors.initials: CE
authors.lastname: Teunissen
authors.affiliation: Alzheimer Center Limburg, School for Mental Health and Neuroscience (MHeNS), Maastricht University Medical Center, P.O. Box 616, 6200 MD, Maastricht, The Netherlands. nico.rozendaal@maastrichtuniversity.nl.
authors.forename: Nico
authors.initials: N
authors.lastname: Rozendaal
authors.affiliation: Alzheimer Center Limburg, School for Mental Health and Neuroscience (MHeNS), Maastricht University Medical Center, P.O. Box 616, 6200 MD, Maastricht, The Netherlands. f.verhey@maastrichtuniversity.nl.
authors.forename: Frans R J
authors.initials: FR
authors.lastname: Verhey
authors.affiliation: Alzheimer Center Amsterdam, VU Medical Center Amsterdam, Amsterdam, The Netherlands. wm.vdflier@vumc.nl.
authors.forename: Wiesje M
authors.initials: WM
authors.lastname: van der Flier
mesh_terms: D000047:Academies and Institutes; D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000175:diagnosis; D016229:Amyloid beta-Peptides / Q000097:blood; D053327:Apolipoprotein E4 / Q000097:blood; D018070:Biological Specimen Banks; D015415:Biomarkers / Q000097:blood / Q000134:cerebrospinal fluid; D003072:Cognition Disorders / Q000175:diagnosis; D060825:Cognitive Dysfunction / Q000175:diagnosis; D015331:Cohort Studies; D004247:DNA / Q000032:analysis; D016208:Databases, Factual; D003704:Dementia / Q000175:diagnosis; D003937:Diagnosis, Differential; D042241:Early Diagnosis; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008499:Medical Records; D008569:Memory Disorders / Q000175:diagnosis; D008875:Middle Aged; D009426:Netherlands; D019636:Neurodegenerative Diseases / Q000175:diagnosis*; D011446:Prospective Studies
chemical_list: D016229:Amyloid beta-Peptides; D053327:Apolipoprotein E4; D015415:Biomarkers; D004247:DNA