Reference Intervals for Plasma Amyloid β in Korean Adults Without Cognitive Impairment.

Amyloid β (Aβ) peptides are important components of plaques in patients with Alzheimer's disease (AD). Recent studies suggest that a low plasma ratio of Aβ42 to Aβ40 may precede the development of the sporadic form of AD. The aim of this study was to establish reference intervals for plasma Aβ in Korean adults. A total of 370 apparently healthy individuals (181 males and 189 females aged 40-69 yr) without cognitive impairment were enrolled. Plasma concentrations of Aβ40 and Aβ42 were measured by using a human amyloid β assay kit (Immuno-Biological Laboratories, Japan). Reference intervals were established according to the "CLSI guidelines for defining, establishing, and verifying reference intervals in the clinical laboratory". There was no need to partition the data with respect to gender or age group. The 95th percentile reference intervals for Aβ40 and Aβ42 were 127-331 pg/mL and 2.31-19.84 pg/mL, respectively. The reference interval for the Aβ42/Aβ40 ratio was 0.011-0.092. Plasma Aβ concentrations obtained in this study could be used as reference intervals for clinical purposes.