Stability of CSF beta-amyloid(1-42) and tau levels by APOE genotype in Alzheimer patients

Cerebrospinal fluid (CSF) measures of beta-amyloid(1-42 )and tau differ between patients with Alzheimer's Disease (AD) and elderly normal controls. The effect of time and APOE genotype on these biomarkers continues to be elucidated. We assessed CSF beta-amyloid(1-42) and tau in 20 mild-to-moderate AD patients, 11 APOE epsilon4+ and 9 APOE epsilon4-, over a mean time of 3.8 years (range 1-11.1 years). Over the period measured, CSF beta-amyloid(1-42) levels were lower in APOE epsilon4+ compared to APOE epsilon4- patients, and the levels decreased over time. Tau levels were stable over time and did not show an effect of APOE allele. While this is a limited clinical sample, the further decrease in CSF beta-amyloid(1-42 )(i.e., more abnormal) combined with the CSF tau stability over a mean period of almost 4 years suggests that beta-amyloid(1-42 )and tau maintain their potential usefulness as diagnostic biomarkers over time. These findings should be taken into account if CSF beta-amyloid(1-42) and tau are used as measures of treatment response.