Serum (blood)

Serum (/ˈsɪərəm/) is the fluid and solvent component of blood which does not play a role in clotting.^[1] It may be defined as blood plasma without the clotting factors, or as blood with all cells and clotting factors removed. Serum contains all proteins except clotting factors (involved in blood clotting), including all electrolytes, antibodies, antigens, hormones; and any exogenous substances (e.g., drugs, microorganisms). Serum also does not contain all the formed elements of blood, which include blood cells, white blood cells (leukocytes, lymphocytes), red blood cells (erythrocytes), and platelets.^{[citation needed]}

The study of serum is serology. Serum is used in numerous diagnostic tests as well as blood typing. Measuring the concentration of various molecules can be useful for many applications, such as determining the therapeutic index of a drug candidate in a clinical trial.^[2]

To obtain serum, a blood sample is allowed to clot (coagulation). The sample is then centrifuged to remove the clot and blood cells, and the resulting liquid supernatant is serum.^[3]