CRP, known as C-reactive protein, is a protein that binds to the podococcal C polysaccharide of Streptococcus pneumoniae to form a complex. This protein is rapidly elevated during the acute phase of the inflammatory process and is increased in some patients with acute and chronic infections, tissue injuries, malignancies, rheumatic diseases, and radiation exposure. C-reactive protein is used clinically to determine postoperative complications of some diseases, to identify infections, and for risk assessment of some cardiac diseases. The tests are conventional C-reactive protein and ultrasensitive C-reactive protein. Ultrasensitive C-reactive protein is a good indicator of heart disease risk grading, and it has a cut-off value of 3.0 mg/L. When it is less than 3.0 mg/L, the risk of heart disease is low, and greater than 3.0 mg/L is high.