Relationship between apoE genotype and CSF β-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 of Alzheimer's disease (AD). The study included 41 definite AD cases, 80 patients with probable AD, 27 with other dementias and 39 neurological controls. 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 in 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. Ninety-one percent of the patients with A beta 42 below the cutoff value (340 pg/ml) and tau above the cutoff value (380 pg/ml) had AD. AD patients carrying 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 epsilon 4 allele non-carriers. Low A beta 42 and high tau concentration in CSF strongly 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 carriers. (C) 2000 Elsevier Science Inc. All rights reserved.