Abstract: An in vitro method and a kit for the quantification of antibodies anti-beta amyloid protein in a sample of cerebrospinal fluid comprising the following steps a) concentrating the quantity of said antibodies of said sample with magnetic micro beads coated with macromolecules capable of binding said antibodies b) analysing the concentrated sample obtained in step a) by immunoenzyme assay or by radioimmunoassay; c) analysing a sample comprising antibodies anti-beta amyloid protein having a known titre with the same assay used in step b) and elaborating the related calibration curve, wherein said antibody having a known titre is a murine antibody belonging to the IgG2a or IgG2b class or a human or humanized antibody belonging to the IgG2b or IgGi class.