Ultrasensitive C-reactive protein, also known as high-sensitivity C-reactive protein, is a C-reactive protein in plasma that is synthesized by the liver. The measurement of ultrasensitive C-reactive protein has the following clinical applications: i. It can be used to identify bacterial infections and viral infections. In bacterial infections, ultrasensitive C-reactive protein is elevated, and the more severe the infection, the higher the indicator, while in viral infections it is generally not high. Second, it is one of the strongest predictors of the risk of cardiovascular events, and can predict the susceptibility to acute heart attack or cerebral thrombosis, and clarify its severity and whether it has a good prognosis. Patients with hypertension should be appropriately monitored for elevated ultrasensitive C-reactive protein. Third, to predict the prognosis of malignant tumors, the higher the ultrasensitive C-reactive protein, the worse the prognosis. IV. Identify whether SLE is active or not. A significantly elevated ultrasensitive C-reactive protein indicates that the disease is in an active stage.