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

The standardization and clinical validation of the measurement of beta -amy loid((1-42)) (A beta (42)) in cerebrospinal fluid (CSF), plasma and urine i s described using a commercially available sandwich-type ELISA with 21F12 a nd 3D6 as monoclonal antibodies. The INNOTEST(TM) beta -amyloid((1-42)) all ows 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 t he detection limit. In plasma, no differences were found in A beta (42) lev els between controls and patients with different neurodegenerative disorder s (Alzheimer's disease (AD), Lewy body disease (LBD), others). In contrast, CSF-A beta (42) concentrations were lower in AD and LBD patients as compar ed to controls. No correlation was found in AD patient between CSF and plas ma concentrations of A beta (42) or between CSF A beta (42) levels and bloo d-brain-barrier function. The quantitative outcome of the test is in part d ependent on confounding factors such as tube type, freeze/thaw cycles, temp erature of incubation, standard preparation protocol, and antibody selectio n. Notwithstanding these aspects, it emerged that A beta (42) is a useful b iochemical 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.