Measurement of β amyloid protein in cerebrospinal fluid as an aid in diagnosis of Alzheimer's disease

Objective To study the diagnostic value of β amyloid protein (Aβ) content in cerebrospinal fluid (CSF) of Alzheimer's disease(AD) patients. Methods Aβ levels were measured by ELISA method with monoclonal antibody against Aβ1 40 in AD(n=12), normal controls (n=24) and Parkinson's disease with dementia (n=6).Results The A values for AD patients were 0 221 0 308 with mean value of 0 255±0 060. In normal controls, the A values were 0 255 0 567 with mean of 0 412±0 097.The mean value for AD was significantly different from that of the normal control group. For Parkinson's disease group, the A values were 0 228 0 380, the mean was 0 313±0 003, it was not significantly different from the mean value for normal controls. The Aβ1 40 level was positively correlated with the severity of AD symptoms, but not with duration. Conclusions Aβ1 40 level in CSF of AD was significantly lower than that in normal controls. It decreased as severity of disease increased, but it did not correlate with duration of AD symptoms. At present, it is yet difficult to conclude whether Aβ has any diagnostic value for AD.