Concentration of Serum Amyloid P Component in the CSF as a Possible Marker of Cerebral Amyloid Deposits in Alzheimer′s Disease

Abstract

Serum amyloid P component (SAP) is a normal plasma protein produced in the liver and co-deposited with amyloid fibrils in all types of amyloidosis, including cerebral β-protein amyloid deposits associated with Alzheimer′s disease (AD). We have measured its concentration and those of α 2-macroglobulin, IgG and albumin in the CSF of 51 patients with AD and 50 healthy and disease control subjects. The mean levels of SAP were 12.8 ng/ml in AD and 8.5 ng/ml in controls (P<0.0125); there was no difference in the levels of the other proteins studied. The observed concentrations of SAP were much lower than expected for a protein of molecular weight 254620. The difference between AD and controls suggests that the concentration of SAP in the CSF may be affected by the presence of cerebral amyloidosis.