The Clinical Utility of Standard and High-Sensitivity C-Reactive Protein: A Narrative Review

Abstract

C-reactive protein (CRP) is an acute phase protein predominantly produced in the liver and regulated by pro-inflammatory cytokines. CRP belongs to the pentraxin family and is involved in the innate immunity due to its functional properties including complement activation, phagocytosis, and apoptosis. CRP exists in two conformationally different forms: pentameric CRP (pCRP) and monomeric CRP (mCRP), having distinctive bioactivities during inflammatory processes. CRP is a non-specific serum biomarker of infection, inflammation, and tissue damage. Cumulative evidence showed that increased CRP concentrations help in the diagnosis, prognosis, and treatment monitoring of many acute and chronic inflammatory diseases. Over the past three decades, numerous studies were focused on the analytical precision of high-sensitivity CRP (hs-CRP) assays and their ability to detect lower levels of circulating CRP. Furthermore, several data reported that elevated levels of hs-CRP strongly predict the risk of cardiovascular diseases; thus, individuals at high and intermediate risk could benefit from intensive lifestyle measures and preventive therapeutic strategies. Additionally, CRP was recently considered as a valuable indicator of COVID-19 severity and mortality. This narrative review is focused on discussing the clinical usefulness of standard CRP and hs-CRP in a wide range of inflammatory conditions, namely: cardiovascular diseases, infections including COVID-19, diabetes mellitus, metabolic syndrome, cancers, rheumatic diseases, neurological disorders, gastrointestinal diseases, periodontitis, chronic kidney disease, asthma, sickle cell disease, surgery, transplant rejection, depression, pregnancy, and systemic lupus erythematosus.