C reactive protein (CRP) is an annular, pentameric protein found in human plasma whose levels rise in response to inflammation. It is synthesised by the liver in response to factors released by macrophages and fat cells. CRP plays a major role in activating the complement system. It is mainly used as a cardiac and inflammation marker. It is used as a positive control in CPR test kits and also used for the manufacturing of calibrators and controls in various in vitro diagnostic kits.