This test measures the concentration of serum amyloid-A (SAA) protein in the blood. SAA is one of the major acute-phase proteins produced by the liver in response to inflammatory signals (cytokines such as IL-1 and IL-6). Its level rises very rapidly (within 6–8 hours) from the onset of inflammation or injury and returns to normal just as quickly after the causative agent is removed, making it an excellent marker for monitoring acute and chronic inflammatory activity.