Changes in core biomarkers in cerebrospinal fluid and cognitive ability in patients with Alzheimer's disease: A two-year longitudinal study

CSF was collected from patients or healthy elderly volunteers by lumbar puncture. Patients were punctured every 6 months over a 2-year period (5 collections), whereas controls were only punctured at baseline. CSF was collected directly into small cryovials in ice-water, and frozen within 30 minutes. No CSF samples were centrifuged. Erythrocyte counts in the CSF were on average 1.7/mL (range 1 5). Polypropylene tubes (Corning) were used throughout, and all samples were stored at -80 oC until analysis.