Objective: Plasma Ab levels have been examined in sporadic Alzheimer’s disease (AD) patients yielding conflicting results. Some studies showed no difference between plasma concentrations of Ab1-42 and Ab1-40 in sporadic cases of AD as compared to controls (Ida et al 1996; Tamaoka et al 1996). Others found increased levels of Ab1-42 in at least some AD patients (Matsubara et al 1999; Kuo et al 1999). Finally the results of one study suggest that high plasma levels of Ab1-42 in healthy people might represent a risk factor of developing AD (Mayeux et al 1999).
Design: Plasma levels of Ab species etsblished in a pilot group of sporadic AD as compared to normal controls and mild cognitive impairment (MCI)
Materials and Methods: Levels of Ab1-40 and Ab1-42 were measured in plasma from 28 patients with AD, 12 subjects with MCI and 12 controls by means of a commercially available ELISA.
Results: Mean plasma Ab1-42 levels were significantly higher in MCI as compared to both AD (p<0.005) and control subjects (p<0.005). Levels of Ab1-40 were marginally higher in AD in the AD group than in controls (p=0.048) but not in MCI. Ab1-40/Ab1-42 ratio could correctly classify all MCI subjects as contrasted to both AD cases and controls. No correlations were observed between Ab species levels and age or MMSE scores.
Conclusion: Mean plasma levels of Ab peptides differ between AD, MCI and control subjects though their usefulness in differential diagnosis of AD is doubtful. Further studies including bigger numbers of subjects are needed to establish the utility of Ab peptides levels in identifying patients with mild cognitive impairment and (possibly) in prediction of their progressing to clinically overt AD.
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