A blood culture is a test in which peripheral blood is drawn from a patient and placed in a culture flask for culture to observe whether colonies form. Generally, the price of blood culture is about 300 RMB, which may vary in different levels of hospitals and different regions. In clinical practice, blood culture is often used for patients with unexplained fever to find out whether there are pathogenic microorganisms invading the blood through blood culture, and it can also do drug sensitivity test at the same time to guide clinical treatment. In addition, blood culture is often used in patients with malignant tumors after chemotherapy, and most of them will have fever when they have a severe reduction of granulocytes during the myelosuppression phase. However, due to the decrease of granulocyte count, the root cause of fever is often difficult to be detected by ordinary examination, and then blood culture is needed to find out whether the infection is sepsis or bacteraemia.