Complement, AP50 total alternative pathway & CH50/THC total classical pathway function
The complement cascade is activated as part of the innate immune response to pathogens. It is also involved in removing immune complexes and apoptotic debris from the circulation.
These assays measure the ability of serum complement components to form the terminal membrane attack complex (MAC) via the classical and the alternative pathway. The MAC forms cytotoxic pores in the membrane of microbes leading to direct killing. These tests are used as a screening test for defects of individual components of the classical, alternative and terminal pathways and in the investigation of immune deficiency. It should not be used for monitoring complement consumption, instead request C3 and C4 levels.
These tests measure formation of the C5b-9 terminal MAC by ELISA.
Suspected complement deficiency
AP50 – 50-125% of normal
|Sample & container required
|Serum (RST rust top)
|5-10 mL blood (1 mL serum)
|For external users, separate and freeze immediately. Transport frozen. For internal users, transport to Charing Cross Hospital Immunology ASAP