Sant Pau Memory Unit, Department of Neurology, Institut d'Investigacions Biomèdiques Sant Pau, Hospital de Sant Pau, Universitat Autònoma de Barcelona, Barcelona, Spain; Centro de Investigación Biomédica en Red en Enfermedades Neurodegenerativas, CIBERNED, Spain. Electronic address: [Email]
OBJECTIVE : To assess the potential influence of the ratio between the storage tube surface area and the volume of cerebrospinal fluid (CSF) (surface/volume) on the quantifications of four Alzheimer's disease (AD) biomarkers on the Lumipulse G600II automated platform. METHODS : CSF samples of 10 consecutive patients were stored in 2 ml polypropylene tubes containing four different CSF volumes: 1.5 ml, 1 ml, 0.5 ml and 0.25 ml. Concentration of CSF Aβ1-42, Aβ1-40, t-Tau and p-Tau were measured in all aliquots using the LUMIPULSE G600II automated platform from Fujirebio. RESULTS : Levels of CSF Aβ1-42 and Aβ1-40 were lower in samples stored with lower volumes (higher surface/volume ratios). This decrease was partly compensated by using the ratio Aβ1-42/Aβ1-40. Quantification of t-Tau and p-Tau were not influenced by this pre-analytical condition. CONCLUSIONS : The surface/volume ratio can potentially influence the results of amyloid AD biomarkers. It appears essential to take into account the surface/volume ratio of the storage tubes when quantifying CSF biomarkers in clinical routine.