Soluble biomarkers may differentiate psoriasis from psoriatic arthritis.

Patients with psoriatic arthritis (PsA) have a higher inflammatory burden and poorer quality of life compared to patients with psoriasis without PsA. Early identification of PsA may prevent joint damage progression and improve quality of life. Soluble biomarkers have the potential to be useful for screening patients with psoriasis for underlying PsA so that appropriate referral to a rheumatologist is made. Pilot studies have shown that C-reactive protein, interleukin 6, cartilage oligomeric matrix protein (COMP), Dickkopf-1, and macrophage-colony stimulating factor may differentiate PsA from psoriasis without PsA. Compared with controls, increased serum levels of receptor activator of nuclear factor-κB ligand, tumor necrosis factor superfamily member 14, matrix metalloproteinase-3 (MMP-3), and COMP are independently associated with psoriatic disease. Increased levels of high-sensitivity CRP (hsCRP), osteoprotegerin (OPG), MMP-3, and the ratio of C-propeptide of type II collagen (CPII) to collagen fragment neoepitopes Col2-3/4 C(long mono) (C2C) are independently associated with PsA. A combination of hsCRP, OPG, MMP-3, and the ratio CPII of C2C was able to distinguish patients with PsA from those with psoriasis alone in a receiver-operating characteristic curve analysis, with area under the curve 0.904. Therefore, a combination of the above biomarkers may at least have a role in screening patients with psoriasis for PsA. These findings need to be validated in prospective studies.