title: Amyloid negativity in patients with clinically diagnosed Alzheimer disease and MCI.
abstract: OBJECTIVE
  To examine the clinical and biomarker characteristics of patients with amyloid-negative Alzheimer disease (AD) and mild cognitive impairment (MCI) from the Alzheimer's Disease Neuroimaging Initiative (ADNI), a prospective cohort study.
  
  
  METHODS
  We first investigated the reliability of florbetapir- PET in patients with AD and patients with MCI using CSF-Aβ1-42 as a comparison amyloid measurement. We then compared florbetapir- vs florbetapir+ patients with respect to several AD-specific biomarkers, baseline and longitudinal cognitive measurements, and demographic and clinician report data.
  
  
  RESULTS
  Florbetapir and CSF-Aβ1-42 +/- status agreed for 98% of ADs (89% of MCIs), indicating that most florbetapir- scans were a reliable representation of amyloid status. Florbetapir- AD (n = 27/177; 15%) and MCI (n = 74/217, 34%) were more likely to be APOE4-negative (MCI 83%, AD 96%) than their florbetapir+ counterparts (MCI 30%, AD 24%). Florbetapir- patients also had less AD-specific hypometabolism, lower CSF p-tau and t-tau, and better longitudinal cognitive performance, and were more likely to be taking medication for depression. In MCI only, florbetapir- participants had less hippocampal atrophy and hypometabolism and lower functional activity questionnaire scores compared to florbetapir+ participants.
  
  
  CONCLUSIONS
  Overall, image analysis problems do not appear to be a primary explanation of amyloid negativity. Florbetapir- ADNI patients have a variety of clinical and biomarker features that differ from their florbetapir+ counterparts, suggesting that one or more non-AD etiologies (which may include vascular disease and depression) account for their AD-like phenotype.
authors.affiliation: From Helen Wills Neuroscience Institute (S.M.L., A.H., W.J.J.), University of California, Berkeley; and Life Sciences Division (S.M.L., A.F., W.J.J.), Lawrence Berkeley National Laboratory, CA. slandau@berkeley.edu.
authors.forename: Susan M
authors.initials: SM
authors.lastname: Landau
authors.affiliation: From Helen Wills Neuroscience Institute (S.M.L., A.H., W.J.J.), University of California, Berkeley; and Life Sciences Division (S.M.L., A.F., W.J.J.), Lawrence Berkeley National Laboratory, CA.
authors.forename: Andy
authors.initials: A
authors.lastname: Horng
authors.affiliation: From Helen Wills Neuroscience Institute (S.M.L., A.H., W.J.J.), University of California, Berkeley; and Life Sciences Division (S.M.L., A.F., W.J.J.), Lawrence Berkeley National Laboratory, CA.
authors.forename: Allison
authors.initials: A
authors.lastname: Fero
authors.affiliation: From Helen Wills Neuroscience Institute (S.M.L., A.H., W.J.J.), University of California, Berkeley; and Life Sciences Division (S.M.L., A.F., W.J.J.), Lawrence Berkeley National Laboratory, CA.
authors.forename: William J
authors.initials: WJ
authors.lastname: Jagust
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000000981:diagnostic imaging* / Q000378:metabolism*; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D015415:Biomarkers / Q000378:metabolism; D060825:Cognitive Dysfunction / Q000000981:diagnostic imaging* / Q000378:metabolism*; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging; D008297:Male; D010446:Peptide Fragments / Q000378:metabolism*; D049268:Positron-Emission Tomography; D011446:Prospective Studies
chemical_list: D016229:Amyloid beta-Peptides; D015415:Biomarkers; D010446:Peptide Fragments; C075222:amyloid beta-protein (1-42)