Increased Cerebrospinal Fluid Aβ38/Aβ42 Ratio in Alzheimer Disease

Abstract

We quantitated amyloid β peptide (Aβ) 38, Aβ40 and Aβ42 levels in matched CSF and plasma from Alzheimer disease (AD) patients and controls. CSF Aβ38 and Aβ40 levels were similar in AD patients and in controls; however, they were higher in controls with APOE υ4 allele than those without. CSF Aβ42 levels were lower in AD patients than in controls. The CSF Aβ38/42 ratio was higher in AD patients than controls, consistent with the previously reported higher Aβ40/42 ratio. Aβ38, Aβ40 and Aβ42 levels in plasma were similar in AD patients and in controls and showed no relationship to levels in CSF. Our findings suggest that the increased CSF Aβ38/42 ratio found in AD patients is derived entirely from reduction of CSF Aβ42 levels.