Confounding factors influencing amyloid beta concentration in cerebrospinal fluid

Abstract

Background. Patients afflicted with Alzheimer's disease (AD) exhibit a decrease in the cerebrospinal fluid (CSF) concentration of the 42 amino acid form of -amyloid (A 42). However, a high discrepancy between different centers in measured A 42 levels reduces the utility of this biomarker as a diagnostic tool and in monitoring the effect of disease modifying drugs. Preanalytical and analytical confounding factors were examined with respect to their effect on the measured A 42 level. Methods. Aliquots of CSF samples were either treated differently prior to A 42 measurement or analyzed using different commercially available xMAP or ELISA assays. Results. Confounding factors affecting CSF A 42 levels were storage in different types of test tubes, dilution with detergent-containing buffer, plasma contamination, heat treatment, and the origin of the immunoassays used for quantification. Conclusion. In order to conduct multicenter studies, a standardized protocol to minimize preanalytical and analytical confounding factors is warranted. Copyright © 2010 Maria Bjerke et al.