Cerebrospinal Fluid Biomarker Analysis

Blood was collected after overnight fasting, just prior to the lumbar puncture, in polypropylene tubes (for serum) or polypropylene K3-EDTA tubes (for plasma), according to widely accepted recommendations for sample handling [21 (link),22 (link)]. Tubes were centrifuged at 2000× g 15 min and the collected serum or EDTA plasma was aliquoted in polypropylene tubes (1 mL each) and stored at −80 °C within 30 min. Frozen serum or plasma aliquots were transferred in dry ice to the Neurologic Clinic and Policlinic, at the University Hospital Basel, Switzerland, for determination of τ_P-181. For the latter, the method described by Karikari et al. (2020) [11 (link)], was performed using the commercially available Simoa (single molecule array) pTau-181 Advantage V2 Kit, on a Simoa HD-X analyzer (Quanterix Corporation, 900 Middlesex Tumpike, Billerica, MA, USA).