Serum amyloid protein A (SAA) levels in Amyloidosis and other disorders

Serum amyloid protein A (SAA) levels were determined in the various sera from patients with amyloidosis (76 cases), non amyloid diseases such as chronic inflammatory diseases (5 cases), collagen diseases (23 cases), malignant diseases (23 cases), and normal controls (69 persons).SAA levels were measured by liquid phase radioimmunoassay techniques using anti-human amyloid A (AA) protein. In brief, alkali degraded amyloid A (DAA) was labeled with 2mCi125I (125I-DAA). One hundred microliter of sera was incubated with 125I-DAA for 48hours in the presence of rabbit anti-AA protein. Each experiment was accompanied by serial dilutions of DAA to obtain the standard curve.Among amyloid cases, SAA levels were elevated in 84.2% of patients in AA type amyloidosis (19_??_ cases), _??_whereas in AL type amyloidosis SAA levels were elevated in 53.2% of 26 patiellts. SAA is also elevated in 35.3% of 51 non-amyloid cases, in contrast to 1.4% of normal controls.As serum SAA levels elevated not only in cases with amyloidosis but in non-amyloid diseases, elevation of SAA is not specific for amyloidosis. However, prolonged elevation of SAA in longstanding chronic inflammatory diseases and malignant diseases may be one of the major pathogenetic signals of secondary amyloidosis.In an attempt to correlate SAA levels with several markers related to inflammation, there was a positive correlation between SAA levels and CRP.