Relationship between apoE genotype and CSF beta-amyloid (1-42) and tan in patients with probable and definite Alzheimer's disease

We investigated the usefulness of cerebrospinal fluid (CSF) beta-amyloid42 (A beta 42), beta-amyloid40 (A beta 40) and tau analyses in the diagnosis o f Alzheimer's disease (AD). The study included 41 definite AD cases, 80 pat ients with probable AD, 27 with other dementias and 39 neurological control s. A beta 42, A beta 40 and tau protein concentrations in CSF were measured of using ELISA assays. A beta 42 levels were decreased and tan increased i n AD. Combination of A beta 42 and tau resulted a sensitivity of 50.4% for AD and specificities of 94.8% for controls and 85.2% for other dementias. N inety-one percent of the patients with A beta 42 below the cutoff value (34 0 pg/ml) and tau above the cutoff value (380 pg/ml) had AD. AD patients car rying apoE epsilon 4 allele had lower A beta 42 (P < 0.005) and higher tau (P < 0.05) levels than those without an epsilon 4 allele, and 18 (81.8%) of the 22 AD patients who had normal A beta 42 and tau levels were apoE epsil on 4 allele non-carriers. Low A beta 42 and high tau concentration in CSF s trongly support the diagnosis of AD. Measurement of A beta 42 may help the early diagnosis of cases at risk for AD such as apoE epsilon 4 allele carri ers. (C) 2000 Elsevier Science Inc. All rights reserved.