Effects of processing and storage conditions on amyloid beta (1-42) and tau concentrations in cerebrospinal fluid: implications for use in clinical practice.
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.
Schoonenboom
Niki S M
NS
Alzheimer Center and Department of Neurology, VU University Medical Center, 1081 HV Amsterdam, The Netherlands. niki.schoonenboom@vumc.nl
Mulder
Cees
C
Vanderstichele
Hugo
H
Van Elk
Evert-Jan
EJ
Kok
Astrid
A
Van Kamp
Gerard J
GJ
Scheltens
Philip
P
Blankenstein
Marinus A
MA
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*
D016229:Amyloid beta-Peptides; D015415:Biomarkers; D010446:Peptide Fragments; C075222:amyloid beta-protein (1-42); D016875:tau Proteins