There is no direct correlation between the level of C-reactive protein and the severity of the disease, so a C-reactive protein of 50 mg/L or more does not mean that the disease is more severe. There is a positive correlation between the degree of elevation and the degree of infection. 1. C-reactive protein, whose normal value is less than 10mg/L, rises sharply in plasma when the body is infected or damaged by tissue injury. C-reactive protein can activate complement and enhance phagocytosis, thus removing pathogenic microorganisms that invade the body as well as damaged, necrotic and apoptotic tissue cells. 2. C-reactive protein rises sharply and exponentially in the hours after the onset of acute inflammation, tissue injury, myocardial infarction, surgical trauma, and major stress trauma. When the disease improves, it rapidly drops to normal, and its elevation is positively correlated with the degree of infection. 3. C-reactive protein can be used as a differential diagnostic indicator for bacterial and viral infections. When the patient has bacterial infection, C-reactive protein is obviously elevated, while when viral infection occurs, C-reactive protein is mostly normal. Therefore, CRP test can effectively guide the application of antibiotics, which can prevent the abuse of antibiotics and the occurrence of drug-resistant bacteria. Usually, only the C-reactive protein elevation does not indicate the severity of the disease, but must be combined with the patient’s clinical symptoms, signs and other examination results, the clinician to comprehensively determine the severity of the disease.