Amyloid β1–40 Quantification in CSF: Comparison between Chromatographic and Immunochemical Methods

Abstract

Background/Aims: Amyloid β (Aβ) is the principal component of senile plaques, one of the hallmarks of Alzheimer’s disease (AD). Evidence is accumulating that soluble aggregates (oligomers) of Aβ are important in the pathogenesis of AD. Methods: We compared three different methods for quantification of the 40 amino acid form of Aβ (Aβ₄₀) in CSF, two based on antibodies [ELISA and surface-enhanced laser desorption/ionization-time of flight (SELDI-TOF) with antibody-coated arrays] and one based on direct binding of proteins to a protein array [SELDI-TOF and immobilized metal affinity [copper] (IMAC30)]. Results: CSF Aβ₄₀ concentration was only found to be significantly elevated in AD (127% of control levels; p = 0.0095) using SELDI-TOF with IMAC30 arrays. Conclusions: These data suggest that the measured Aβ level in CSF may differ depending on whether antibody-based methods are used or not, possibly caused by epitope masking due to Aβ oligomerization or to binding of Aβ to carrier proteins.