Rheumatoid arthritis (RA) is a chronic inflammatory disease of unknown origin that may lead to progressive damage of small and large joints with major functional impairment.

Long-term medical treatment is needed to impede the rheumatic inflammation, to reduce pain and to retain physical function. Several disease modifying anti-

rheumatic drugs (DMARDs) are the most prevalent and effective treatment options;

they intervene during different key processes of the rheumatic inflammatory cascade and thereby slow down disease progression. DMARDs do not exhibit an acute effect; improvement of symptoms occurs usually after several weeks and sometimes months after a patient began a DMARD therapy. The most commonly used DMARD is methotrexate (MTX).

Biologic DMARDs present an important therapeutic innovation. They are used if synthetic (non-biologic) DMARDs are ineffective, or if patients are affected by rapid progressive RA courses. These drugs are produced biotechnologically and follow completely new modes of action; they inhibit either messengers or cells that play essential roles in the rheumatic inflammatory cascade. In 2001, the first biologic DMARDs were licensed in Germany.

When compared to non-biologic DMARDs in clinical trials, biologic DMARDs were found to be very effective and safe. RA patients of such trials are usually selected according to specific disease characteristics and observed over only a short period of time. Therefore, it remains unclear how effective and safe biologic DMARDs are in the long-term if used in routine rheumatologic care. To answer these questions, biologics registers were implemented in several European countries. The registers are observational studies that investigate and compare the courses of disease and therapy in RA patients treated either with biologic or non-biologic DMARDs. The comparison of therapies is also of economic interest, since costs of therapy with biologic DMARDs are particularly high.