Calcitoninogen testing is the detection of calcitoninogen concentration from the blood circulation and is a more specific marker of inflammation for bacterial infections, which helps in the early diagnosis of bacterial infectious diseases. In contrast, calcitoninogen often shows a transient elevation after major surgical procedures, followed by a gradual decline for 2 months. Non-infectious factors that cause elevated calcitoninogen are also systemic diseases, such as phagocytic syndrome, adult Still’s disease, etc.; and the acute phase in specific states, let’s say multiple injuries, major surgery and severe burns, early acute pancreatitis, subacute thyroiditis, etc. In addition, it is seen in patients with tumors and transplants. Bacterial infection of the body causes corresponding clinical symptoms and may also present with abnormal blood tests, such as elevated white blood cell count and neutrophil count, significantly elevated C-reactive protein, and significant abnormalities in blood sedimentation or other markers of inflammatory response in routine blood tests. By using these inflammatory response markers, patients can be determined to have a possible bacterial infection, but the specificity is not particularly strong, and significant elevations may also occur in viral infections. The clinical use of calcitoninogen testing will be able to determine more specifically whether a significant bacterial infection is present.