title: Cerebrospinal Fluid Levels of Amyloid Beta 1-43 in Patients with Amnestic Mild Cognitive Impairment or Early Alzheimer's Disease: A 2-Year Follow-Up Study.
abstract: BACKGROUND
  Biomarkers that will reliably predict the onset of Alzheimer's disease (AD) are urgently needed. Although cerebrospinal fluid (CSF) amyloid beta 1-42 (Aβ42), total tau, and phosphorylated tau can be used to complement the clinical diagnosis of AD, amnestic mild cognitive impairment (aMCI), the prodromal phase of AD, is heterogeneous. Biomarkers should be able to determine which patients with aMCI are at greatest risk of AD. Histological studies and animal models indicate that amyloid beta 1-43 (Aβ43) aggregates early, and may play a role in the pathological process of AD. We have examined levels of CSF Aβ43 in a 2-year longitudinal study of aMCI and early AD.
  
  
  METHODS
  Cerebrospinal fluid was collected at baseline, and after one and 2 years from patients with AD (n = 19), and patients with aMCI (n = 42). Of these, 21 progressed to AD during the 2 years of study, whereas 21 did not. Controls (n = 32) were lumbar punctured at baseline only. CSF analyses of Aβ43, Aβ42, and total tau were carried out with ELISA.
  
  
  RESULTS
  At baseline, CSF Aβ43, CSF Aβ42 and ratios with total tau could be used to separate controls from all three patient groups. CSF Aβ43, but not Aβ42, could separate patients with aMCI who progressed to AD during the 2 years of follow-up, from those that did not. The CSF total tau/Aβ43 ratio had a slightly but significantly larger area under the receiver operating characteristic curve when compared to the CSF total tau/Aβ42 ratio. CSF Aβ43 levels, but not Aβ42 levels, decreased from baseline to 2 years in the AD group.
  
  
  CONCLUSIONS
  CSF Aβ43 was demonstrated to be significantly reduced in patients already by the time that aMCI or AD was diagnosed, compared to controls, and this change must have occurred during the preclinical period. Since our results suggested that CSF Aβ43 distinguishes between subgroups of patients with aMCI better than CSF Aβ42, it may prove to be a useful additional biomarker for identifying aMCI patients at greatest risk of AD.
authors.affiliation: Department of Neuroscience, Faculty of Medicine, Norwegian University of Science and Technology Trondheim, Norway.
authors.forename: Camilla
authors.initials: C
authors.lastname: Lauridsen
authors.affiliation: Department of Neuroscience, Faculty of Medicine, Norwegian University of Science and TechnologyTrondheim, Norway; Department of Neurology, University Hospital of TrondheimTrondheim, Norway.
authors.forename: Sigrid B
authors.initials: SB
authors.lastname: Sando
authors.affiliation: Department of Neuroscience, Faculty of Medicine, Norwegian University of Science and Technology Trondheim, Norway.
authors.forename: Adiba
authors.initials: A
authors.lastname: Shabnam
authors.affiliation: Department of Neurology, University Hospital of Trondheim Trondheim, Norway.
authors.forename: Ina
authors.initials: I
authors.lastname: Møller
authors.affiliation: Department of Neuroscience, Faculty of Medicine, Norwegian University of Science and Technology Trondheim, Norway.
authors.forename: Guro
authors.initials: G
authors.lastname: Berge
authors.affiliation: Department of Neuroscience, Faculty of Medicine, Norwegian University of Science and TechnologyTrondheim, Norway; Department of Neurology, University Hospital of TrondheimTrondheim, Norway.
authors.forename: Gøril R
authors.initials: GR
authors.lastname: Grøntvedt
authors.affiliation: Norwegian Institute of Public Health Oslo, Norway.
authors.forename: Inger J
authors.initials: IJ
authors.lastname: Bakken
authors.affiliation: Unit for Applied Clinical Research, Faculty of Medicine, Norwegian University of Science and Technology Trondheim, Norway.
authors.forename: Øyvind
authors.initials: Ø
authors.lastname: Salvesen
authors.affiliation: Department of Neuroscience, Faculty of Medicine, Norwegian University of Science and TechnologyTrondheim, Norway; Department of Neurology, University Hospital of TrondheimTrondheim, Norway.
authors.forename: Geir
authors.initials: G
authors.lastname: Bråthen
authors.affiliation: Department of Neuroscience, Faculty of Medicine, Norwegian University of Science and TechnologyTrondheim, Norway; Department of Neurology, University Hospital of TrondheimTrondheim, Norway.
authors.forename: Linda R
authors.initials: LR
authors.lastname: White
keywords: Alzheimer’s disease; amnestic mild cognitive impairment; amyloid beta 1–42; amyloid beta 1–43; biomarkers; cerebrospinal fluid; diagnostic accuracy