This kit is used for quantitative determination of serum amyloid A (SAA) in human serum, plasma or whole blood in vitro. Serum amyloid A (SAA) is an acute phase reaction protein with a molecular weight of 12 KD. Under normal circumstances, the content of SAA in blood is very small. In the acute stage of inflammation or infection, SAA increases rapidly within 48-72 hours, and decreases rapidly in the recovery stage of disease. It has been shown that serum SAA can be detected in bacteria, virus infection, atherosclerosis, coronary heart disease, acute transplant rejection and other diseases. Similar to C-reactive protein (CRP), SAA is helpful to diagnose inflammation, evaluate its activity, detect its activity and treatment. In the acute stage of viral infection, the level of SAA was significantly higher than that of CRP, so SAA is a sensitive and reliable indicator for the diagnosis of viral infection. Combined detection of SAA and CRP can improve the sensitivity of diagnosis of infection, and help to differential diagnosis of bacterial infection and viral infection.