Prediction of Alzheimer's disease using the CSF Aβ42/Aβ40 ratio in patients with mild cognitive impairment

Evidence supports an important role for beta-amyloid (A beta) in the pathogenesis of Alzheimer's disease ( AD). Here, we investigate baseline levels of the 40- and 42-amino-acid-long A beta peptides (A beta 40 and A beta 42) in cerebrospinal fluid (CSF) from a cohort of patients with mild cognitive impairment (MCI, n = 137) in relation to the final diagnosis after 4 - 6 years of follow-up time. CSF A beta 42 concentration at baseline and the A beta 42/A beta 40 ratio were significantly decreased in the MCI patients who developed AD as compared to cognitively stable MCI patients and MCI patients who developed other forms of dementia ( p < 0.001). The baseline levels of A beta 40 were similar in all MCI groups but correlated with change in Mini Mental State Examination scores in converters to AD. The A beta 42/A beta 40 ratio was superior to A beta 42 concentration with regard to identifying incipient AD in MCI ( p < 0.05). In conclusion, the data provide further support for the view that amyloid precursor protein metabolism is disturbed in early sporadic AD and points to the usefulness of the A beta 42/ A beta 40 ratio as a predictive biomarker for AD. Copyright (C) 2007 S. Karger AG, Basel.