Usefulness of the determination of C reactive protein and other acute phase proteins in rheumatoid arthritis [Utilità del dosaggio della proteina C reattiva e di altre proteine della fase acuta nell'artrite reumatoide]

The acute phase response is defined as a large number of diverse reactions which attempt to adjust the organism to the effects of stress/injury. It is now clear that there is a complex interaction between the cytokines with interleukin-6 predominant, but also involving interleukin-1, tumor necrosis factor and a group of recently described cytokines including as well interleukin-11, leukaemia inhibitory factor and oncostatin M all of which influence the levels of acute phase proteins. In clinical practice, C reactive protein (CRP) is frequently used as marker of the acute-phase response. It has a short half-life and consequently it is a sensitive measure of cytokine-induced protein synthesis. In rheumatoid arthritis (RA) the rate appearance of bony erosions in the early phase of the disease correlated with the mean serum concentration of CRP in some studies. A recent study examining the rate of spinal trabecular bone loss in the first year of rheumatoid disease found a strong correlation between bone loss and serum CRP concentrations. It appears that CRP concentrations reflect the level of 'systemic osteoclast-activating factor' and are, therefore, a good measure of the general catabolic state of the patient. Many would now consider that persistently elevated serum CRP in patients with RA is in itself an indication for immunosuppressive therapy.