Biomarkers of rheumatoid arthritis: recent progress.

IMPORTANCE OF THE FIELD: Biomarkers are emerging as vital tools for early diagnosis, prognostication and disease management in chronic diseases, including rheumatoid arthritis (RA). AREAS COVERED IN THIS REVIEW: This review discusses diagnostic, prognostic and theranostic biomarker candidates for RA that are being studied at present. WHAT THE READER WILL GAIN: The reader will gain a better understanding of the different classes of markers being proposed as potential biomarkers for RA, and how they compare with each other. TAKE HOME MESSAGE: At present, several molecules are showing varying degrees of promise as potential biomarkers in RA. These include serum rheumatoid factors and anti-cyclic citrullinated protein antibodies, a couple of acute phase proteins and pro-inflammatory cytokines expressed in the serum and/or diseased joints, notably IL-1, IL-6, TNF-α, MCP-1 and MIP-α, as well as molecules released by damaged synovial tissue, cartilage and bone. Continuing proteomic and metabolomic efforts are rapidly expanding this repertoire of potential biomarker candidates. Large-scale longitudinal trials are clearly needed where several biomarker candidates can be assessed in parallel, relative to current yardsticks. The ultimate goal is to distill out a subset of informative biomarkers, presumably representing distinct pathogenic pathways, which will enable the rheumatologist to prognosticate, predict and actively manage the disease course in RA.