Biological markers in rheumatoid arthritis.

Rheumatoid arthritis is characterized by chronic inflammation associated with considerable damage to the musculoskeletal system, particularly in and around diarthrodial joints. By using newly developed immunoassays and chemically based assays for cartilage-, bone-, and synovium-derived molecules, which are products of synthesis and/or degradation, it is now possible to detect the release of these molecules and their degradation products into body fluids such as serum, synovial fluid, and urine. This release is influenced significantly by the inflammatory process and reflects the damage caused to these tissues by chronic inflammation. Some new markers for skeletal metabolism are reviewed and examples are given of how they determine the damaging effects of this chronic inflammatory disease on these tissues before changes are observed radiologically. Some of these markers have both prognostic value and potential for rapidly interpreting the effects of therapy.