Pd. Mehta et al., Plasma and cerebrospinal fluid levels of amyloid beta proteins 1-40 and 1-42 in Alzheimer disease, ARCH NEUROL, 57(1), 2000, pp. 100-105
Background: In brains with AD, A beta is a major component of diffuse plaqu
es. Previous reports showed that CSF A beta 42 levels were lower in patient
s with AD than in controls. Although studies showed higher plasma A beta 42
levels in familial AD, a recent report has indicated that plasma A beta 42
levels were similar in a sporadic AD group and controls. However, no infor
mation is published on plasma A beta 40 and A beta 42 levels in relation to
Apo E genotype or severity of dementia in sporadic AD.
Objective: To examine plasma and cerebrospinal fluid (CSF) levels of amyloi
d beta protein 1-40 (A beta 40) and 1-42 (A beta 42) levels in patients wit
h probable Alzheimer disease (AD) and elderly nondemented control subjects
in relation to the apolipoprotein E (Apo E) genotype and dementia severity.
Setting: Two university medical centers.
Patients and Methods: Levels of A beta 40 and A beta 42 were measured in pl
asma from 78 patients with AD and 61 controls and in CSF from 36 patients w
ith AD and 29 controls by means of a sandwich enzyme-linked immunosorbent a
ssay.
Results: Mean plasma A beta 40 levels were higher in the AD group than in c
ontrols (P = .005), but there was substantial overlap; A beta 42 levels wer
e similar between the groups. Levels of A beta 40 and A beta 42 showed no a
ssociation with sex or Mini-Mental State Examination scores. There was a si
gnificant relationship between age and A beta 40 level in controls but not
in the AD group. Levels of A beta 40 were higher in patients with AD with t
he Apo E epsilon 4 allele than in controls (P < .01). Cerebrospinal fluid A
beta 40 levels were similar in the AD group and controls. However, A beta
42 levels were lower in the AD group than in controls (P < .001). The level
s showed no association with severity of dementia.
Conclusions: Although mean plasma A beta 40 levels are elevated in sporadic
AD and influenced by Apo E genotype, measurement of plasma A beta 40 level
s is not useful to support the clinical diagnosis of AD. Lower levels of CS
F A beta 42 in the AD group are consistent with previous studies.