There are two methods for the routine determination of complement: 1. Hemolysis method: It is mainly used to check the activity of classical and bypass pathways. Total complement, referred to as CH50, is determined by the hemolysis method, also known as the test tube method. Complement C1-C9 is activated by antibody (hemolysin) sensitized sheep erythrocytes and causes lysis of the latter. There is a certain range between complement activity and the degree of hemolysis, such as 20%-80% hemolysis, within which there is a positive correlation. 50% hemolysis is generally used as the discriminating point, and the final CH50 concentration is calculated by calculation. 2. Immunochemical method: It is mainly used for the determination of complement content of C3, C4, etc. C3 and C4 are determined by immunochemical method, and most clinical laboratories currently use coarse-grained scattering, i.e., in a specific The measurement of C3 and C4 is performed by immunochemical method, and most clinical laboratories use coarse-grained scattering, i.e., measurement at a specific unit or above, or transmission turbidimetry on a biochemical instrument, where the antigen and antibody react in the liquid phase to produce turbidity, and within a certain concentration range, the complement content is proportional to the turbidity, at which time the complement C3 and C4 concentrations can be derived by conversion.