Plasma ß-amyloid1-42 reference values in cognitively normal subjects.

BACKGROUND: In clinical practice, the use of plasma ß-Amyloid1-42 (Aß1-42) as biomarker for Alzheimer's disease is largely limited by the absence of reference values. The aim of this study was to evaluate Aß1-42 plasma concentrations in cognitively normal subjects and to propose reference values. METHODS: Plasma samples were obtained from 245 subjects, with a wide age-range (19-89 years), enrolled at the Unit of Laboratory Medicine of the "Azienda Ospedaliera Cardinale G. Panico" (younger subjects) and from a population-based study on aging (GreatAGE study) (older subjects). Three different age-groups were established: young (≤ 34), adult (35 ≤ age ≤ 64) and old (>64). The Innogenetics Elisa kit for plasma Aß1-42 was used for the analysis. RESULTS: The mean (SD) concentration of plasma Aß1-42 was 17.65 (5.71) pg/mL. A positive trend was found in Aß1-42 levels across the three age groups (p < .0001): young subjects showed values of Aß1-42 significantly lower than the adult group (p < .0001) and than the old one (p < .0001 overall); no significant differences were found between the adult and the old groups (p = 1.0000). For the entire cohort the lower limit of 90% Reference Interval, double-sided, was 8.12 pg/mL (95% CI 6.77-9.45) and the upper limit was 29.00 pg/mL (95% CI 27.01-31.00). CONCLUSION: The present study proposes reference values for plasma Aß1-42. Nevertheless, further studies are needed to confirm these results and corroborate the use of these reference values in clinical practice.