OBJECTIVE: To better understand the seemingly contradictory plasma beta-amyloid (Abeta) results in Alzheimer's disease (AD) patients by using a newly developed plasma Abeta assay, the INNO-BIA plasma Abeta forms, in a multicenter study. METHODS: A combined retrospective analysis of plasma Abeta isoforms on mild cognitive impairment (MCI) from three large cross-sectional studies involving 643 samples from the participating German and Swedish centers. RESULTS: Detection modules based on two different amino (N)-terminal specific Abeta monoclonal antibodies demonstrated that Abeta in plasma could be reliable quantified using a sandwich immunoassay technology with high precision, even for low Abeta42 plasma concentrations. Abeta40 and Abeta42 concentrations varied consistently with the ApoE genotype, while the Abeta42/Abeta40 ratio did not. Irrespective of the decrease of the Abeta42/Abeta40 ratio with age and MMSE, this parameter was strongly associated with AD, as defined in this study by elevated hyperphosphorylated (P-tau181P) levels in cerebrospinal fluid (CSF). CONCLUSION: A highly robust assay for repeatedly measuring Abeta forms in plasma such as INNO-BIA plasma Abeta forms might be a useful tool in a future risk assessment of AD.
