Serum calprotectin in immune-mediated inflammatory rheumatic diseases: a new biomarker of inflammation

In immuno-mediated rheumatic diseases (IMRD), laboratory biomarkers, which include autoantibodies, proteins of the acute phase of inflammation, cytokines, markers of endothelial damage, components of the complement system, subpopulations of lymphocytes, indicators of bone metabolism, and many others, occupy a central place in the diagnosis, assessment of activity, and monitoring of the effectiveness of pharmacotherapy. In the range of biomarkers of inflammation in recent years, special attention has been drawn to calprotectin (CP), which is a heterodimeric complex of S100A8 and S100A9 calcium-dependent proteins. Currently, to characterize inflammation in IMRD, attention is drawn to determining the concentration of CP in biological fluids, the so-called circulating or serum (s) CP, an increase in the concentration of which may be more associated with local (in situ) than with systemic synthesis of protein. The narrative review summarizes the clinical significance of the sCP determination in IMRD as a new biomarker of inflammation. Preliminary recommendations regarding indications for determining the sCP in IMRD are presented.