Why C-reactive protein is one of the most requested tests in clinical laboratories?

C-reactive protein (CRP) is an acute-phase protein which is synthesized by the liver in response to the secretion of several inflammatory cytokines including interleukin 6 (IL-6), IL-1 and tumor necrosis factor (TNF). CRP was the first acute-phase protein to be described and adopted in clinical laboratories as an exquisitely sensitive systemic marker of inflammation and tissue damage. The measurement of CRP is widely used for the diagnosis and monitoring of inflammatory conditions, including sepsis, trauma, and malignancies. In the last decades, impressive advances in analytical methods (from qualitative to high-sensitivity assays), automation and availability of results in a short time, not only translated in an increasing demand for the right management of systemic inflammatory diseases, but also in evaluating subclinical inflammatory processes underlying atherothrombotic events. CRP measurement is one of the most requested laboratory tests for both the wide range of clinical conditions in which it may assure a valuable information and some analytical advantages due to the evidence that it is a "robust biomarker". Even recently, the measurement of CRP received new interest, particularly as a biomarker of severity of Coronavirus disease 2019 (COVID-19), and it deserves further concern for improving demand appropriateness and result interpretation.