Standardization of measurement of β-amyloid(1-42) in cerebrospinal fluid and plasma

The standardization and clinical validation of the measurement of beta -amyloid((1-42)) (A beta (42)) in cerebrospinal fluid (CSF), plasma and urine is described using a commercially available sandwich-type ELISA with 21F12 and 3D6 as monoclonal antibodies. The INNOTEST(TM) beta -amyloid((1-42)) allows the specific and reliable measurement of (1-42) amyloid peptides in CSF and plasma. The A beta (42) concentrations in serum and urine were below the detection limit. In plasma, no differences were found in A beta (42) levels between controls and patients with different neurodegenerative disorders (Alzheimer's disease (AD), Lewy body disease (LBD), others). In contrast, CSF-A beta (42) concentrations were lower in AD and LBD patients as compared to controls. No correlation was found in AD patient between CSF and plasma concentrations of A beta (42) or between CSF A beta (42) levels and blood-brain-barrier function. The quantitative outcome of the test is in part dependent on confounding factors such as tube type, freeze/thaw cycles, temperature of incubation, standard preparation protocol, and antibody selection. Notwithstanding these aspects, it emerged that A beta (42) is a useful biochemical marker for the diagnosis of AD patients, but there is a need for an international A beta standard, a universally accepted protocol for CSF preparation, and a thorough evaluation of assay performance in function of the boundary conditions.