title: Fluctuations of CSF amyloid-beta levels: implications for a diagnostic and therapeutic biomarker.
abstract: OBJECTIVE
  To investigate the stability and time course of human CSF amyloid-beta (Abeta) levels over hours.
  
  
  METHODS
  Fifteen nondemented participants had CSF sampled hourly for up to 36 hours via indwelling lumbar catheter. CSF Abeta(1-x), Abeta(1-40), and Abeta(1-42) were measured by ELISA in each hourly CSF sample.
  
  
  RESULTS
  Significant variation in Abeta levels of 1.5- to fourfold was detected over 36 hours of serially sampling in individual subjects. Abeta(40), Abeta(42), and Abeta(1-X) are highly correlated over time indicating that similar processes likely regulate the level of these species. On average, the fluctuations of Abeta levels appear to be time of day or activity dependent.
  
  
  CONCLUSIONS
  Diagnostic and therapeutic trials that measure Abeta should control for the time of CSF sampling to minimize variability.
authors.affiliation: Dept. of Neurology, Washington University School of Medicine, St. Louis, MO 63110, USA. batemanr@wustl.edu
authors.forename: Randall J
authors.initials: RJ
authors.lastname: Bateman
authors.forename: Guolin
authors.initials: G
authors.lastname: Wen
authors.forename: John C
authors.initials: JC
authors.lastname: Morris
authors.forename: David M
authors.initials: DM
authors.lastname: Holtzman
mesh_terms: D000328:Adult; D000368:Aged; D000544:Alzheimer Disease / Q000134:cerebrospinal fluid / Q000175:diagnosis / Q000628:therapy; D016229:Amyloid beta-Peptides / Q000134:cerebrospinal fluid*; D015415:Biomarkers / Q000134:cerebrospinal fluid; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013997:Time Factors
chemical_list: D016229:Amyloid beta-Peptides; D015415:Biomarkers