SAA2 and rheumatoid arthritis: SAA concentrations were found to be significantly higher in the sera than in the synovial fluids of patients with RA (mean levels: 3.6 ± 2.1 and 2.3 ± 1.4 μg/mL, P < 0.01, Figure 8A), suggesting that chronic arthritis stimulates production of SAA from extraarticular sources such as the liver, thus contributing to the higher level of SAA in sera.