title: Effects of processing and storage conditions on amyloid beta (1-42) and tau concentrations in cerebrospinal fluid: implications for use in clinical practice.
abstract: BACKGROUND
  Reported concentrations of amyloid beta (1-42) (A beta 42) and tau in cerebrospinal fluid (CSF) differ among reports. We investigated the effects of storage temperature, repeated freeze/thaw cycles, and centrifugation on the concentrations of A beta 42 and tau in CSF.
  
  
  METHODS
  Stability of samples stored at -80 degrees C was determined by use of an accelerated stability testing protocol according to the Arrhenius equation. A beta 42 and tau concentrations were measured in CSF samples stored at 4, 18, 37, and -80 degrees C. Relative CSF concentrations (%) of the biomarkers after one freeze/thaw cycle were compared with those after two, three, four, five, and six freeze/thaw cycles. In addition, relative A beta 42 and tau concentrations in samples not centrifuged were compared with samples centrifuged after 1, 4, 48, and 72 h.
  
  
  RESULTS
  A beta 42 and tau concentrations were stable in CSF when stored for a long period at -80 degrees C. CSF A beta 42 decreased by 20% during the first 2 days at 4, 18, and 37 degrees C compared with -80 degrees C. CSF tau decreased after storage for 12 days at 37 degrees C. After three freeze/thaw cycles, CSF A beta 42 decreased 20%. CSF tau was stable during six freeze/thaw cycles. Centrifugation did not influence the biomarker concentrations.
  
  
  CONCLUSIONS
  Repeated freeze/thaw cycles and storage at 4, 18, and 37 degrees C influence the quantitative result of the A beta 42 test. Preferably, samples should be stored at -80 degrees C immediately after collection.
authors.affiliation: Alzheimer Center and Department of Neurology, VU University Medical Center, 1081 HV Amsterdam, The Netherlands. niki.schoonenboom@vumc.nl
authors.forename: Niki S M
authors.initials: NS
authors.lastname: Schoonenboom
authors.forename: Cees
authors.initials: C
authors.lastname: Mulder
authors.forename: Hugo
authors.initials: H
authors.lastname: Vanderstichele
authors.forename: Evert-Jan
authors.initials: EJ
authors.lastname: Van Elk
authors.forename: Astrid
authors.initials: A
authors.lastname: Kok
authors.forename: Gerard J
authors.initials: GJ
authors.lastname: Van Kamp
authors.forename: Philip
authors.initials: P
authors.lastname: Scheltens
authors.forename: Marinus A
authors.initials: MA
authors.lastname: Blankenstein
mesh_terms: D000368:Aged; D000544:Alzheimer Disease / Q000175:diagnosis; D016229:Amyloid beta-Peptides / Q000134:cerebrospinal fluid* / Q000592:standards; D015415:Biomarkers / Q000134:cerebrospinal fluid; D002498:Centrifugation; D005260:Female; D005615:Freezing; D006361:Heating; D006801:Humans; D008297:Male; D008875:Middle Aged; D010446:Peptide Fragments / Q000134:cerebrospinal fluid* / Q000592:standards; D011177:Postal Service; D013048:Specimen Handling; D013997:Time Factors; D016875:tau Proteins / Q000134:cerebrospinal fluid*
chemical_list: D016229:Amyloid beta-Peptides; D015415:Biomarkers; D010446:Peptide Fragments; C075222:amyloid beta-protein (1-42); D016875:tau Proteins