AMYLOID-BETA PROTEIN IN PLASMA FROM PATIENTS WITH SPORADIC ALZHEIMERS-DISEASE

Fibrillar amyloid beta protein (A beta) deposition is increased in the brains of patients with Alzheimer's disease (AD), and is manifested a s senile plaques (SPs) and congophilic angiopathy (CA). A beta 40 and A beta 42(43), two chief species of A beta, are documented in SPs and CA, as well as in cerebrospinal fluid (CSF) and cell culture media. A beta 42(43) is the major component of diffuse plaques, the earliest fo rm of SPs. Thus, we hypothesized that determination of the amount of A beta 42(43) in CSF or plasma might provide a diagnostic laboratory te st for AD. We measured amounts of different A beta species in plasma f rom 28 patients with sporadic probable AD, 40 age-matched neurologic p atients without dementia and 25 age-matched normal controls using enzy me-linked immunosorbent assays (ELISAs). Plasma concentrations of A be ta 1-40 and A beta 1-42(43) did not significantly differ among these g roups. These findings suggest the unlikelihood that plasma A beta assa ys would be useful as a diagnostic tool for AD.