Pregnancy-associated alpha 2-glycoprotein (alpha 2-PAG) and various acute phase reactants in rheumatoid arthritis and osteoarthritis.

Pregnancy-associated alpha 2-glycoprotein (alpha 2-PAG) concentrations have been measured in matched sera and synovial fluid samples obtained from 36 patients with rheumatoid arthritis and 10 patients with osteoarthritis. Levels of alpha 2-PAG in serum and synovial fluid were significantly higher in rheumatoid arthritis than in osteoarthritis. Calculation of the synovial fluid/serum ratios for alpha 2-PAG gave results which are explicable only if this protein were being synthesised locally. In a longitudinal study of 15 patients with rheumatoid arthritis, concentrations of alpha 2-PAG did not reflect disease activity, unlike those of the classical acute phase reactants, C-reactive protein and caeruloplasmin.