Diagnostic Accuracy of ELISA and Luminex Technology (xMAP) for the Quantitation of CSF Amyloid Beta 40 and 42 Peptides to differentiate Patients with Probable Alzheimer Disease (AD) from Elderly Non-demented Controls (P1.094)

Objective: We hypothesized that irrespective of the differences in antibodies to Aβ 40 or Aβ 42 , analytical platforms or absolute levels of CSF Aβ 40 and Aβ 42 in ELISA or xMAP, both methods would perform equally well to support the diagnosis of patients with probable AD. Background: CSF Aβ 42 levels or Aβ 42 / Aβ 40 ratio are used to support the diagnosis of probable AD. There is a wide range of absolute levels. Such discrepancies reflect the variety of assays, differences in specificities and affinity of Aβ antibodies, and clinical characteristics of cohorts. No data is available that directly compares different antibodies and platforms in identifying AD within the same cohort. Design/Methods: We examined 56 coded CSF samples (39 controls and 17 AD) received from the NYU School of Medicine. Our assay in NY used rabbit monoclonal antibodies to Aβ in a sandwich ELISA. The same samples were also examined in Sweden using mouse monoclonal antibodies to Aβ in xMAP platform (INNO-BIA, Belgium). All analyses were conducted using both parametric and non-parametric statistics where appropriate. Results: Absolute levels in combined groups (AD versus controls) of CSFAβ 4 0 were about 1.3 fold higher in ELISA than those of xMAP, and Aβ 42 were 1.7 fold lower in ELISA than those of xMAP. There was a significant correlation between ELISA and xMAP for CSF Aβ 40 levels (r = .787; p 42 levels (r = .836; p 42 /Aβ 40 ratio (r = .575; p 42 levels or Aβ 42 /Aβ 40 ratios were equally sensitive to support the diagnosis of AD (p Conclusions: Despite differences in assays and Aβ antibodies, the overall performance of the ELISA and xMAP assays was equal to identify AD. Further studies are needed to confirm these findings in large cohorts including autopsy confirmed cases. Study Supported by: NY State OPWDD and Grant from the NIA Disclosure: Dr. Mehta has received royalty payments from Biolegend. Dr. deLeon has nothing to disclose. Dr. Blenow has nothing to disclose. Dr. Zigman has nothing to disclose. Dr. Zetterberg has nothing to disclose.