Update on biomarkers in psoriatic arthritis: a report from the GRAPPA 2010 annual meeting.

Biomarkers may be used to screen patients with psoriasis for psoriatic arthritis (PsA) and to assess disease activity and severity. Candidate biomarkers should fulfil the key features of the OMERACT (Outcome Measures in Rheumatology) filter, that is, truth, discrimination, and feasibility. A number of biomarkers are currently being investigated in psoriatic disease for important clinical outcomes. Serum high sensitivity C-reactive protein, cartilage oligomeric matrix protein, interleukin 6 (IL-6), osteoprotegerin, matrix metalloprotease-3 (MMP-3), and the ratio of C-propeptide of type II collagen (CPII) to collagen fragment neoepitopes Col2-3/4 (long mono) (C2C) show promise as serum biomarkers that distinguish subjects with PsA from those with psoriasis alone. Serum MMP-3 and melanoma inhibitory activity, synovial fluid IL-1, IL-1 receptor-α, IL-6, IL-8, and chemokine CCL3 and synovial tissue CD3-positive T cells may prove useful as biomarkers of PsA activity. Circulating osteoclast precursors, Dickkopf-1, macrophage colony stimulating factor, receptor activator of nuclear factor-κB ligand, and bone alkaline phosphatase are strong candidates as biomarkers of radiographic change. Prospective studies to identify biomarkers for psoriatic disease are high on the research agenda of the Group for Research and Assessment of Psoriasis and PsA.