Rheumatoid arthritis (RA) is a common autoimmune disease affecting around 1% of the population. Although
major advances have been made in the treatment of RA,
still relatively little is known on disease pathogenesis and
aetiology. From treatment studies it has become clear that treating patients early in their disease course will provide the best results. However, especially in the early phase of arthritis, in particular when the patients do not yet fulfil the criteria for RA, it is difficult to decide which patients would benefit most from an early and aggressive intervention. Good biomarkers are important to guide decisions in the clinical management of RA. Next to the well-known rheumatoid factor (RF) and the anti-citrullinated protein antibodies (ACPA), several new markers are now likely to become available with interesting potential. Besides antibody responses directed against citrullinated proteins, also antibodies against carbamylated proteins (anti-CarP) have recently been shown to be present in RA. Interestingly these anti-CarP antibodies are also present in around 20% of
the ACPA-negative RA patients and are associated with more severe joint damage in this group. Apart from the antibodies that help in establishing the diagnosis and prognosis, also novel biomarkers that reflect clinical disease activity scores are being discovered. The development of biomarker-based disease activity scores might allow easy and frequent monitoring of patients to rapidly adjust treatment.