Established and new biochemical tools for diagnosis and monitoring of rheumatoid arthritis.

Rheumatoid arthritis is clinically heterogeneous, and early aggressive therapy is probably not always warranted. A large number of biochemical and biologic markers are under investigation for possible usefulness in diagnostic and prognostic work. These markers can be divided into three main categories: disease specific, inflammatory, and tissue specific. Markers may be useful in the study of prognosis and response to therapy, whereas the diagnostic information they provide is limited. Marker metabolism is largely unexplored, and validation of most marker analyses is lacking. However, they are interesting research tools and may in the end not only teach lessons on the pathogenesis of the disease but also help in selecting patients early for aggressive disease or detecting response or lack of response to therapy.