Serum amyloid A (SAA) concentration varies among rheumatoid arthritis patients estimated by SAA/CRP ratio

Background: C reactive protein (CRP) and serum amyloid A (SAA) are similarly sensitive indicators of inflammation, but discrepancies are recognized in several disease conditions. SAA levels are generally higher and vary more among individuals. The significance of the SAA/CRP ratio was evaluated in the estimation of SAA. Methods: Sera of out-patients with rheumatoid arthritis (RA) and healthy subjects were measured for CRP and SAA cross-sectionally and longitudinally by a highly sensitive latex agglutination turbidimetric imununoassay. The results were classified into four groups according to the CRP concentration, and the SAA/CRP ratios were calculated and evaluated. Results: In the cross-sectional study, CRP and SAA were shown to correlate significantly in sera of patients with RA, but not in healthy subjects. The SAA/CRP ratios were wide RA patients and tended to decrease in the range and mean values were observed depending on the concentration of CRP. In the longitudinal study, variations of the ratio among individuals were wide, but smaller and similar within individuals. The difference in magnitude of the ratios is due to the difference in SAA concentration. Conclusion: Variations of SAA/CRP ratios were affected by SAA concentrations. The ratio should be checked in the evaluation of SAA. (c) 2005 Elsevier B.V. All rights reserved.