• Alzheimer's disease;   • Amyloid β protein;   • CSF;   •
Diagnosis  Abstract: The principal constituent of amyloid
plaques found in the brains of individuals with Alzheimer's
disease (AD) is a 39–42-amino-acid protein, amyloid β protein
(Aβ). This study examined whether the measurement of Aβ levels
in CSF has diagnostic value. There were 108 subjects enrolled in
this prospective study: AD (n = 39), non-AD controls (dementing
diseases/syndromes; n = 20), and other (n = 49). CSF was
obtained by lumbar puncture, and Aβ concentrations were
determined using a dual monoclonal antibody immunoradiometric
sandwich assay. The mean Aβ value for the AD group (15.9 ± 6.8
ng/ml) was not significantly different from that for the non-AD
control group (13.0 ± 7.1 ng/ml; p = 0.07), and substantial
overlap in results were observed. Aβ values did not correlate
with age (r = −0.05, p = 0.59), severity of cognitive impairment
(r = 0.22, p = 0.21), or duration of AD symptoms (r = 0.14, p =
0.45). These findings are in conflict wi