Plasma levels of Aβ peptides are altered in amnestic mild cognitive impairment but not in sporadic Alzheimer's disease

Abstract

Plasma Aβ levels have been examined in sporadic Alzheimer's disease yielding conflicting results; both no difference and an increase in plasma concentrations of Aβ42 and Aβ40 in sporadic cases of AD as compared to controls have been reported. Elevated plasma Aβ42 levels may be detected several years before the onset of symptoms (in mild cognitive impairment stadium). Levels of Aβ40 and Aβ42 were measured in plasma from 54 patients with AD, 39 subjects with MCI and 35 controls using a commercially available ELISA. Mean plasma Aβ42 levels were significantly higher in MCI as compared to both AD (P<0.001) and control subjects (P<0.001), while Aβ40 did not differ between the groups. No correlations were observed between Aβ levels and age, MMSE scores or gender. According to ROC curve analysis the maximum accuracy in discriminating MCI versus both controls and AD subjects has been achieved using a cut-off value of 3.8.