Table 1

Optimal practice for CSF collection and processing

Confounding variableIdeal situation
Preanalytical factors
 Time of collection8:00–12 noon to avoid potential for diurnal variation in CSF biomarkers
 LP needleNeedle gauge or design not known to influence measured biomarker concentration but gauge is related to risk of post-LP headache. Smallest size practical to use in diagnostic LP is 22G. Atraumatic needles are associated with reduced post-LP headache but increased failure rate
 Use of lumbar catheters/manometersAβ1-42 may adhere—to be avoided, if possible
 Collection vesselPolypropylene tube recommended. Aβ1-42 and other proteins adhere to polystyrene and glass significantly reducing measured concentrations. Tube brand may also influence measured biomarker concentrations
 FastingNot required
 Blood contamination/blood–brain barrier dysfunctionBlood contamination of up to 5000 erythrocytes/µL cells does not alter measured biomarker concentration, but blood–brain barrier dysfunction equivalent to CSF/serum albumin ratio >11 results in reduced measured Aβ1-42 concentration and should be interpreted with care
 Optimal volumeIn addition to CSF collected for routine clinical examination (eg, cell count, oligoclonal bands, cytology, etc) 15 mL can safely be collected without increased risk of post LP headache
 CentrifugationWithin 30 min of LP at 3000 rpm for 10 min to remove cells and other debris
 Aliquot storage volumeSamples that are frozen prior to analysis should be stored in aliquots of a standardised volume which fits the tube size well. Specifically, one should strive for as high volume to surface ratio as possible (well-filled tubes). Volume to surface ratio and number of tube transfers influence measured Aβ1-42 concentration, probably due to protein adsorption
 Freeze thawingOne or less freeze thaw cycles is recommended. Measured Aβ1-42 concentration drops by 20% after 3 freeze thaw cycles. Aβ1-42 and τ concentrations are stable at temperatures of −80°C
 Choice of immunoassay/platformConsistency required; variability in commercially available ELISA-based assays, calibration peptides and platforms mean interlaboratory and interassay consistency is poor
  • CSF, cerebrospinal fluid; LB, lumbar puncture.